PDA

View Full Version : Focal Reducers - Squeeze all your FOV and Light on your GH1 Sensor



MatzeB
05-06-2009, 05:06 AM
Astro guys use focal reducer / focal compressor / field flattener to concentrate the wide field of view on their small CCD chips.
The cool thing is that you not only widen your field of view, but also brighten your image, because the whole light is compressed to a smaller area.

check out this page:
http://www.isomedia.com/homes/cvedeler/scope/focal_reducers.htm

Compressing your full frame 35mm Lens to the 2x crop GH1 sensor should theoretically gain 2 stops of light, because the sensor area is 4 times smaler.
That would turn a 50mm f1,4 into a 25mm f0,7 or a 24mm f2,0 into a 12mm f1,0 ! :shocked:

I don't know, if a 0,5x compression is possible while keeping the overall quality of the lens. But one could use a weaker 0,75x reducer - and gain at least the half field and one stop of light.


For a quick experimental observation of the effect take a Macro Diopter and hold it - behind - your lens. Catch your image with a piece of paper or some kind of ground glass. A +10 Diopter is not strong enough - but you will see the effect.

LizaWitz
05-06-2009, 02:19 PM
Very interesting point. Plus your 50mm f1.4 would be a 25mm f0.7, or 50 mm equivilent. Because the image circle would be reduced to fit the image circle of the MFT sensor, resulting in the same field of view.

Less wasted light, same field of view as 35mm.

There's also a fair bit of room between the sensor and the back of a 35mm adapted lens in which to put these optic.

Your light gain from this, though, would be offset by any light loss due to the focal reducer optics... but it sounds like a spectacular idea, all in all!

pix2pixels
05-06-2009, 06:34 PM
Hmmmm,

An interesting article (http://www.iceinspace.com.au/93-458-0-0-1-0.html) about using the FC with telescopes and DSLR cameras.

pix2pixels
05-06-2009, 06:59 PM
From the notes about this Meade focal reducer (http://www.agenaastro.com/Meade-f-3-3-Focal-Reducer-and-Variable-T-Adapter-p/ofr-me-3.3fr.htm), it seems that is not suitable for conventional photographic imaging, but others are. They are only x0.5, but that is not bad if they work. One stop gain, and the approximative equivalent FOV of a FF35mm camera is fantastic.
I also understand that there is a resolution loss, but test will be required.

AwakenedFilms
05-06-2009, 07:03 PM
Who is going to try it and let us know how well it works?

I wonder if zooming in on the GG will negate the increase in light because of the increase in f-stop. Also, grain will become larger and possibly more apparent.

I still think its a cool idea.


J

pix2pixels
05-06-2009, 07:38 PM
The amount of de-magnification is variable, depending of the adapater/spacer length.

It looks that these adapters are not very expensive and trying to 'play' with a series of contraptions of different lens combos would be cool.

Kholi
05-06-2009, 07:46 PM
If someone tells me HOW to do it I'll pick one up.

I don't see HOW though.

MatzeB
05-07-2009, 03:20 AM
From the notes about this Meade focal reducer (http://www.agenaastro.com/Meade-f-3-3-Focal-Reducer-and-Variable-T-Adapter-p/ofr-me-3.3fr.htm), it seems that is not suitable for conventional photographic imaging, but others are. They are only x0.5, but that is not bad if they work. One stop gain, and the approximative equivalent FOV of a FF35mm camera is fantastic.
I also understand that there is a resolution loss, but test will be required.


0,5x is the maximum. The GH1 Sensor has a crop factor of ~ 1,9 in 16/9.
1/1,9 = 0,53...
With a 0,5x reducer you actually should gain 2 stops, because the image AREA
is reduced to 1/4.

MatzeB
05-07-2009, 03:27 AM
Who is going to try it and let us know how well it works?

I wonder if zooming in on the GG will negate the increase in light because of the increase in f-stop. Also, grain will become larger and possibly more apparent.

I still think its a cool idea.


J

I don't think it's a good idea to use it with a 35mm Adapter.
There's nothing you can improve if you already have the Full Frame.
It will only degrade your image.

I'm talking about using it on the smaller GH1 Sensor.

MatzeB
05-07-2009, 03:32 AM
The amount of de-magnification is variable, depending of the adapater/spacer length.

It looks that these adapters are not very expensive and trying to 'play' with a series of contraptions of different lens combos would be cool.

It's definitely worth some experiments.

DanDOF
05-07-2009, 06:11 AM
This might become my new DIY project... goodbye Ground Glass, hello GH1 Sensor! :love4:

Kholi
05-07-2009, 08:26 AM
Again, because i don't understand the concept, if someone tells me how I'll try it?

Steve Castle
05-07-2009, 12:22 PM
Again, because i don't understand the concept, if someone tells me how I'll try it?

What the focal reducer does, the lens is already doing relative to the target sensor/film size. The real point of a focal reducer for a dSLR adapter is to reduce the image circle from a 35mm full-frame, for instance, to a 1.5x crop or 2.0x crop; from its original target size to a smaller one (which is what the OP I think is suggesting).

There are technical problems to this, primarily the focal flange distance being too short to accommodate the necessary optical elements. This is why focal reducers are primarily used on large astronomical telescopes that are simpler to implement. The Borg 77EDII Telescope I posted on the other thread for instance can accommodate a focal reducer.

http://dvxuser.com/V6/showpost.php?p=1626017&postcount=67

To make it really work on a dSLR, you will essentially need an entirely new lens assembly that refocuses the image circle. This obviously will be expensive and would reduce overall optical image quality. The patent below demonstrates how this will need to be accomplished for a dSLR (the "50" area representing the focal reducer):

http://i357.photobucket.com/albums/oo13/steve_castle/Picture3-2.png

Ian-T
05-07-2009, 01:48 PM
I understand that we would be adding more elements in between the lens and sensor....but being that this camera (GH-1) does not use a mirror like traditional DSLRs, how bad would the degradation be? Maybe slightly softer? And gaining some light to boot.

Barry_Green
05-07-2009, 02:43 PM
A mirror wouldn't have any effect on degradation, as the mirror flips up out of the way when shooting anyway... it should have the same effect on a GH1 as it would on any SLR...

pix2pixels
05-07-2009, 04:35 PM
Maybe a product like Optec 0.5 (http://www.optecinc.com/astronomy/ngw_050.htm) could be a starting point

pix2pixels
05-07-2009, 04:43 PM
Some extra info on this page (http://www.optecinc.com/astronomy/nextgen.htm) too.

MatzeB
05-08-2009, 02:51 AM
Without the mirrorbox there should be enough space for an adapter.
I doubt it would be good enough for 12MP photos, but downscaled to 1080 or 720 it might look good.
Here is a quick test of a DIY compressor - just to show, that it should be possible. Looks like it's compressing ~0,7x or 0,8x
Don't judge image quality. It's only to show the effect.

50mm Canon FD at f1,4 :
http://www.dvxuser6.com/uploaded/19323/1241775171.jpg

50mm Canon FD at f1,4 with compressor:
http://www.dvxuser6.com/uploaded/19323/1241775273.jpg

MatzeB
05-08-2009, 03:15 AM
Maybe a product like Optec 0.5 (http://www.optecinc.com/astronomy/ngw_050.htm) could be a starting point

The cheapest way to do some rough tests probably is taking a GH1 to an astronomy shop and try different reducers (handholding).
critical looking vendor included...:huh:

pix2pixels
05-08-2009, 03:21 AM
WOW MatzeB,

Did a similar thing yesterday.
I went to a local telescope shop and they had a Meade telecomprssor on the shelf. Just attached a 16-35mm lens from my Canon camera and got a similar image to yours. I didn't have another camera with me to take a photo.

I was told to look at Optec, but they are available only from US for less than $300. I hope to hear from a local guy that manufactures telecompressors and telescope adapters for DSLRs.

From further reading (http://www.astrovid.com/technical_documents/Optec%20f5%20negen%20focal%20reducer.pdf), I gather that the NextGen 0.5 needs 55mm between the sensor and flange distancel to get 18mm an image circle where they are optimised for best image performance.

MatzeB
05-08-2009, 04:15 AM
From further reading (http://www.astrovid.com/technical_documents/Optec%20f5%20negen%20focal%20reducer.pdf), I gather that the NextGen 0.5 needs 55mm between the sensor and flange distancel to get 18mm an image circle where they are optimised for best image performance.

300$ is a bit too expensive for the first test. And 18mm is a bit too small. But they are made for very long lenses - maybe the size of the image circle and the working distance is totaly different with our short lenses.

For serious tests we have to wait till the GH1 is available.
I think I can make a more or less hard mountable and adjustable ghetto reducer out of T2 rings and this adapter:
http://www.japanexposures.com/shop/product_info.php?products_id=262

pix2pixels
05-08-2009, 04:28 AM
Hopefully I will get in touch and speak to this local (oz) manufacturer and get more information, hope, or a cold shower.

As I mentioned before, just holding a 16mm lens in front of the adaptor, I could see a decent image as you did with yours. Wish I had a GH1 right here, right now.


There a discontinued Optec 0.5x available for ~$90.

Steve Castle
05-08-2009, 11:13 PM
Without the mirrorbox there should be enough space for an adapter.
I doubt it would be good enough for 12MP photos, but downscaled to 1080 or 720 it might look good.
Here is a quick test of a DIY compressor - just to show, that it should be possible. Looks like it's compressing ~0,7x or 0,8x
Don't judge image quality. It's only to show the effect.


The distance afforded between Canon FD and ĩ4/3rds is a mere 22mms. For most focal reducers the critical spacing to maintain is at least 55mms between the sensor and the shoulder (or rear spacer, if required) of the focal reducer coupling. Each focal reducer has a set distance the element should be placed. For the Meade .33x focal reducer it's around 88mm, Optec 0.5 & Borg requires ~55mm. Astronomical image sensor cameras are not designed to a standard distance between the camera interface and imaging sensor, so to have these focal reducers work you will need to consider the spacing very carefully.

What might be easiest is a combination of a bellows system with multiple adapters that can accommodate the assortment of lenses and mounts (Horseman, Novoflex, etc). This way you can adjust the exact distance between the focal reducer and the sensor. A Nikon F-mount with a FFD of 46.5mm might be easier to adapt then a Canon FD, or maybe even Medium-format lenses (RB/RZ/645 etc.) or a PL.

Another thing, there are many ways to implement this beyond the astronomical focal reducers being discussed here. If you would remember the Nikon-Fuji E2/E3 used a similar system, except the focal reducer was aft of the where the sensor/film would be. The Kodak patent I showed previously in this thread was designed around the same time, to adapt 35mm full-frame lenses to smaller CCD sensors. What these companies figured out was that the negative impact of these focal reducers optically wasn't worth the added cost, and as APS-C & 4/3rds sensors started to be released it was more desirable to release lenses catered to those formats rather then implementing complex methods in reducing the image circle on existing lenses.

With that said, I'd be very interested in seeing what results you achieve with your endeavors. . .

http://i357.photobucket.com/albums/oo13/steve_castle/FujixE2Smdm.jpg
http://i357.photobucket.com/albums/oo13/steve_castle/opticalillus.jpg

MatzeB
05-09-2009, 11:35 AM
Thanks Steve for these insights. I've never heard of the E2/E3 before.
From a commercial point of view it makes not sense to hassle with a converter and have a bucket full of compatibility issues when you can sell new lenses or larger sensors.
This is a pure DIY project. It's quite probable that the results will be disappointing. But maybe it rocks or at least give a certain "look".

I have a collection of FD lenses. Therefore I will try these first. But you're right it's easier with Nikon.
I thought about a bellows, but it's too long for a compact adapter. The T2-System is very versatile and I already own a couple of different rings.

MatzeB
05-17-2009, 03:46 PM
There are at least a few professional broadcast reducers out there - thought no one that compresses a 35mm full frame 0,5x.

Vantage Film (Hawk Anamorphics) has two different 0,7x reducers for long lenses.
They gain 1 stop!
http://www.vantagefilm.com/en/news/index_12.shtml
http://www.vantagefilm.com/en/news/index_08.shtml

Abakus sells several different converters - even for c-mount.
http://www.abakus.co.uk/Format_Converters.htm

A suitable converter would be 1000$ minimum from these companies. Probably alot more.


Steven Mogg ( http://moggadapters.com/astro/adapter.asp ) sells inexpensive focal reducers and custom SLR-mount adapters.
@pixel2pixel is that the Oz manufacturer you've mentioned?

TimurCivan
05-17-2009, 04:47 PM
This is how Kubrick managed to shoot Barry Lyndon with Candle light with a Zeiss F.07 50mm lens. it was a Fast medium Format lens with this contraption on the back. the problme was the camera had to be modified to move the film plane because the real element was only a few mm away from the gate..... ti does work... watch barry lyndon.

pix2pixels
05-17-2009, 07:06 PM
Steven Mogg ( http://moggadapters.com/astro/adapter.asp ) sells inexpensive focal reducers and custom SLR-mount adapters.
@pixel2pixel is that the Oz manufacturer you've mentioned?



Yes,

Unfortunately, all my attempts to contact him via email were not successful to date. Still hope to get in touch with him. His expertise and advice would be great.

Looking at Hawk adapters, it seems that the long lenses are suitable to be dealt with. It's worth looking into it to see what would the shortest focal length acceptable.

squig
05-18-2009, 12:50 AM
He's flogging a DSLR focal reducer for 75 bucks.

If anyone can give me an extra stop without too much degradation I'm all ears and shallow pockets.

MatzeB
05-18-2009, 01:11 AM
squig think about an anamorphic reducer...
the wide field is already there on full frame lenses.
You just have to squeeze it.

von Mutius
05-18-2009, 01:31 AM
If there is not enough place why not use a medium format lens, the focal flange distance with those is way longer because of the larger film and mirrorbox...

Just my 2 eurocents:)


Matthias

MatzeB
05-18-2009, 03:01 AM
yeah it could be easier, but you have to compress them stronger.
something about 0,25x - 4 stops gain.
A 50mm f4,0 Flektogon would become a 12,5mm f1,0.
I don't know if such a strong compression is possible.

j
05-18-2009, 10:16 AM
Do you retain DOF with focal reducers?

MatzeB
05-18-2009, 11:39 AM
No - I don't think so.

You get lower f-stops. That could give you shallower DOF.
But if there's enough light it's probably better to stop the lens down.

AwakenedFilms
05-18-2009, 01:36 PM
Getting closer...Very interesting!


J

squig
05-18-2009, 06:29 PM
squig think about an anamorphic reducer...
the wide field is already there on full frame lenses.
You just have to squeeze it.

that's exactly what I'm thinking

DanDOF
06-05-2009, 09:01 PM
I found this Focal Reducer simulator about half way down the page:

http://www.wilmslowastro.com/software/formulae.htm

timbook2
06-08-2009, 02:27 PM
extremely interesting thread :)

Matze ::thumbup:

ick komm nach Berlin in 2-3 Wochen, können wir uns mal kurzschliessen???

Postmaster
06-08-2009, 02:56 PM
Just fo the record:

Iīm using medium format Zeiss primes on my LEX.
They behave exactly what the numbers say.

Like a 80mm medium format looks like a 80mm 35mm lens.
Same DOF and FOV.

But of course the collect a much bigger circle than the GG can show.
A stronger condenser or a bigger gg would do the trick.
I would prefer a biger GG thou because of the grain.
I could zoom out much more and maybe the grain would vanish at all without spinning or vibrating the GG.

An anamorphic reducer would be the cream thou.

Frank

TimurCivan
06-08-2009, 03:58 PM
Do you retain DOF with focal reducers?

yes. its the same image circle. it will look like the native capturing lens.

TimurCivan
06-08-2009, 04:03 PM
Just fo the record:

Iīm using medium format Zeiss primes on my LEX.
They behave exactly what the numbers say.

Like a 80mm medium format looks like a 80mm 35mm lens.
Same DOF and FOV.

But of course the collect a much bigger circle than the GG can show.
A stronger condenser or a bigger gg would do the trick.
I would prefer a biger GG thou because of the grain.
I could zoom out much more and maybe the grain would vanish at all without spinning or vibrating the GG.

An anamorphic reducer would be the cream thou.

Frank

perhaps im misunderstanding... do you have a focal reducer on your medium format lenses? because a 80mm would look like a 105 or 110 on a 35mm Film plane.

j
06-08-2009, 06:59 PM
Do you retain DOF with focal reducers?
yes. its the same image circle. it will look like the native capturing lens.

Then where were these during the EPIC Edwierdo thread?

Postmaster
06-09-2009, 03:01 AM
perhaps im misunderstanding... do you have a focal reducer on your medium format lenses? because a 80mm would look like a 105 or 110 on a 35mm Film plane.

Thatīs what I thought and everyone told me in the first place - but itīs wrong.
With a 50mm medium format Zeiss prime I get the same FOV and DOF as with a 50mm Nikon prime made for 35mm photo cameras on my LEX.

Donīt ask me how it works but itīs a fact. Look at the pictures:
First one is 4.0 50mm Zeiss medium format
Second one is 1.4 50mm Nikon (35mm photo prime)

And no, I donīt have a reducer. I just mentioned it because there was always some missunderstanding when it comes to medium format lenses.

But I wish I would have a reducer or even better an anamorphic reducer.

MatzeB
06-14-2009, 11:30 AM
A 50 is a 50 is a 50 is a 50 - regardless the size of the chip.
The difference between a 50mm SLR Lens and a 50mm medium format lens is the size of the image circle.
If you add a focal reducer or doubler it's no longer a 50.

There's a lot of 'crop factor' confusion out there.

Rabot
06-30-2009, 04:56 AM
Sorry to revive this but it was tointeresting to keep it out.

What's up yet with Focal Reducer?

DanDOF
07-27-2009, 10:01 PM
I've been wondering, does a focal reducer change the back focus distance (focal flange distance) of the photography/telescopic lens?

If it doesn't it seems impossible to fit any focal reducer between GH1 and lens, even if an adapter was made to move the FR within the camera body towards the sensor
(about 20mm of space from Micro 4/3 mount to sensor).

All the focal Reducers I've found have a focal length greater than the focal flange distance of a Nikon lens (46.5mm).

For example, according to http://www.wilmslowastro.com/software/formulae.htm#FR

the focal length of the following Focal Reducers are:
- Atik 0.5x = 80mm
- Celestron 0.63x = 285mm
- Meade 0.33x = 85mm


The Meade/Celestron focal reducers have the following focal lengths.
[note: Since around 2006 Meade 0.63 focal reducers have a focal length of around half what they should be making them unsuitable for use with SLR cameras or filter wheels]:

FR 0.33x focal length = 85mm
FR 0.63x focal length = 285mm
William Optics 0.8x FR focal length = 260mm
ATIK 0.5x FR focal length = 80mm
* Note that the in-focus figure assumes that the FR-CCD spacing is added to your physical imaging train length (as when using the Meade/Celestron FR's with spacing tubes). If you are using a FR like the ATIK that is fitted internally, then you have to add the FR-CCD spacing to this figure (to make it smaller). If you are using a FR like the Meade/Celestron then you will have to subtract the depth of the FR itself to this figure (to make it a larger negative number).


Anyway, I think this thread may be a lost cause now.

seb33
08-07-2009, 02:08 PM
link for focal reducers and nikon or canon adaptator, in french sorry

http://www.m42optic.fr/pro/catalog/index.php?cPath=44_24_90&osCsid=402993813eb649358a5a21bb4f700b3a

seb33
08-09-2009, 09:26 AM
read here :

http://www.bautforum.com/astronomical-observing-equipment-accessories/55902-focal-reducer-slr-camera.html

"I've never seen one and there may be a reason. Putting in a FR requires shortening the distance between telescope object and the FR versus where the sensor (film) would normally be without it. For example, I have an Orion ED80 telescope and a 0.5 focal reducer. The FR should be (and normally is) a fixed distance from the sensor (film) as this distance determines the actuall reduction amount - more distance = greater reduction. Without the FR, my camera can't focus without adding about a 2" extension tube to the optics train. With the FR (at a distance that yields 0.5x) in its proper place at the end of the camera's 'snout' the focus is just fine without any extension tube. By using a longer 'snout' to achieve more like 0.4x or 0.35x ), the camera cannot go into the telescope's tube far enough to focus.

Consequently, I would expect that to insert a FR in a camera/lens system, one must move the lens away from the sensor (film) in order to insert the FR while the optics demands that the sensor (film) be located closer to the lens if there is a FR added - which in the general case is likely to be an impossibility.

On the opposite end of things, barlow lenses used to be available for slr cameras for 2x and 3x increase in effective FL. However, those require separating lens from sensor (film) which was no problem."

commanderspike
08-09-2009, 03:50 PM
I see no reason why a focal reducer can't work on the GH1 and the first person who sticks a Micro 4/3rds mount on the end of one is going to be a millionaire :)

Yet a quick look around and they're all for telescopes! Crazy...

The diagram of the old Nikon DSLR with small CCD sensor showed the imaginary film plate behind the lens. The lens works as normal and the focal reducer simply delivers the image to the sensor at half the size and double the brightness.

I can't wait for somebody to actually make one... it can't be that hard? The optics already exist.

My only concern is over image quality. Sure the image will be brighter and you could probably get away with lower ISOs than you normally could, but the lens won't be more sensitive to light. It'll still be an F1.4 for example. It's just that the sensor will be more sensitive to the image. But I bet that some subtleties from the image will be washed out and the focal reducer would have to have some damn good glass in it to keep hold of all the image's resolution at 0.5x.

Revsta
02-12-2010, 12:37 PM
So any updates on this? i'm looking to shoot a feature soon and it would be awesome to have a focal reducer instead of investing in 7.5mm lenses.

alignment1
02-12-2010, 03:23 PM
yeah, I'm real late to the party- but this sounds great--very Edwierdo thread-ish!! I love it- another holy grail to chase.

Anything...

Anyone??...

Z

NURBS
06-04-2010, 12:29 PM
Hey Guys'

Me interesting this theme too, I'm bought 0.5x Focal reducer. Fastest test show very nice result. I'll do new adapter for this reducer and show result.

Test result will be soon. ;-)

dvbrother
06-04-2010, 02:39 PM
NURBS,

Where did you buy the 0.5x adapter? How did you attach it to the GH1?
Yes, please show the results of your test soon!

jleo
06-04-2010, 05:06 PM
Panasonic Patent for Electronic focal reducer and auto focus for M43 cameras and interchangeable lenses: The PDF has diagrams.

http://www.freepatentsonline.com/y2010/0091175.html

dvbrother
06-04-2010, 07:34 PM
Panasonic Patent for Electronic focal reducer and auto focus for M43 cameras and interchangeable lenses: The PDF has diagrams.

http://www.freepatentsonline.com/y2010/0091175.html

Jleo,

Are you sure that's the correct link? I didn't see anything about a focal reducer.

jleo
06-04-2010, 09:17 PM
Sorry, I'll have to recheck. Thought I read somewhere about focal length correction ie without crop factor.

Here's the CNET article about the patent:

http://asia.cnet.com/crave/2010/04/19/putting-the-mirrors-back-in-micro-four-thirds-cameras/

NURBS
06-06-2010, 04:50 AM
First fastest test from a hand, reducer photos have lot of flares and optical distortions. (soon will be with new adapter). :Drogar-BigGrin(DBG)

Nikkor 50mm f/8

Rabot
06-06-2010, 05:33 AM
Hum, this doesnt look this bad. would you mind sharing the focal reducer used ?

kainekainekaine
08-06-2010, 09:54 AM
NURBS did you ever get any further with the Focal Redeucer Adapter? Which Focal Reducer did you use? Cheers

tonpole
08-28-2010, 05:55 PM
Dont be so gullible.

hopeless_4ever
11-03-2010, 04:13 AM
I've succeeded in adapting a 0.6x focal reducer to my E-P1. This forum thread helped me a lot, which is why I'm eager to share the results soon and keep this topic alive.

Originally, I hoped to use it on some of my longer C-mount lenses, like my Fujinon 50/1.4. However, due to the micro 4/3 flange focal distance, it's impossible. Forget about Olympus and Panasonic lenses too. Nikon lenses work though. I've tested with a Rokinon 8/3.5 fisheye and Nikkor 105/2.5. My guess is that T-Mount lenses would work as well, with proper adapters and/or adjustments.

Because the focal reducer is 0.6x, I get sensor coverage that's maybe slightly bigger than APS-C but definitely not full frame. Quality-wise, the results are similar to what NURBS posted. I get a decently sharp picture, but lower contrast. Lens speed is doubled.

As for DOF, I don't know yet. I'm still trying to fashion a proper mount for it. My workmanship is kind of shoddy (metal file and super glue for everything), and I'm only using some spare parts I have at hand.

pix2pixels
11-03-2010, 04:54 AM
Welcome to the forum. Your efforts sound really interesting, I would say very exciting.
Please keep us in the loop if possible.
Looks like cine lenses in PL mount with a flange distance of 52mm can be a good candidate for the 4/3 format.
BNCR is even longer.

gmoe
11-03-2010, 09:28 AM
Yes, hopeless_4ever please post the focal reducer you were using and the mounts that you used to get it to work. Any sample pics as of yet?

hopeless_4ever
11-04-2010, 04:44 AM
I used a Vixen 0.6x C-mount reducer. Funny enough, it never actually worked with my C-mount lenses. The rear fit into a C-mount just fine, but the front (female part) was made for 1.25" eyepieces. It might be good for astronomy and telescoping, but pretty useless for general photography. It was expensive too, something like $185 used if I remember correctly. I know there are cheaper reducers out there, but I bought this one thinking it will work with C-mount lenses, as the name implies. I was wrong. This reducer has been discontinued now and is almost impossible to find online.

I unscrewed the actual reducer from its original mount and put it through a regular C-mount to micro 4/3 adapter that I got off Ebay. I filed the adapter's opening to allow for the reducer's larger diameter. Then, I had to file the front and back "hoods" to get the optic closer to the sensor, and closer to the lens. It is all held in place by superglue. When mounted, it's a very tight fit; I really can't get the reducer any closer to the sensor without hitting something or getting it jammed.

Here is how it looks like:


http://img17.imageshack.us/img17/1604/jswreducer1.jpg




Today, I took a few test shots right after I came back from work. The sun was setting down, so the lighting was changing quickly. ISO800 for all pictures, camera set in P mode for automatic shutter selection. Because I'm still working on attaching a permanent Nikon mount to the reducer, the following pictures were taken holding the lens manually in front of the reducer. Any blur or flare you see is probably caused by me tilting the lens or not holding it steady enough; It was REALLY hard for me to keep my hands steady. There also seems to be some light pollution, causing lower contrast. I'm confident that these problems will not show when I finally attach a proper Nikon mount to the reducer. If there is anyone in Chicago area who wants to help me, please let me know!


The lens hood from the fisheye is always seen in the frame with the reducer on. It doesn't show on APS-C, which means that the coverage is slightly bigger than APS-C but definitely not full frame.

http://img25.imageshack.us/img25/6756/jswreducer2.jpg
http://img683.imageshack.us/img683/3931/jswreducer3.jpg



The flare seen in the photo with the reducer on is not common. I think it happened as a result of light coming in from the side as I was holding the lens by hand. When I try to seal off the combo to prevent straight light from coming in, I notice no flare and the contrast gets better too - but I needed a free hand to snap the picture!

http://img151.imageshack.us/img151/7107/jswreducer4.jpg
http://img243.imageshack.us/img243/4772/jswreducer5.jpg



For this last one, I was trying to test depth-of-field at equal focal length, so the photos were taken at different distances. Obviously, with the reducer on, I had to move the camera closer to get the same view.

http://img5.imageshack.us/img5/3880/jswreducer6.jpg
http://img69.imageshack.us/img69/5384/jswreducer7.jpg



I really hope to finish a proper housing for this combo soon. I have some old Nikon macro extenders that, when stacked, get pretty close to what I want, but still a few millimeters short of what I need for infinity focus. I wish I was a machinist... Haha.

Any suggestions or ideas?

pix2pixels
11-04-2010, 07:43 AM
Another reducer from Optec (http://www.optecinc.com/astronomy/ngc316.htm): this one covers more than the diagonal of a 35mm stills camera.

hopeless_4ever
11-04-2010, 08:30 AM
Another reducer from Optec (http://www.optecinc.com/astronomy/ngc316.htm): this one covers more than the diagonal of a 35mm stills camera.

However, we don't need that much coverage for micro 4/3 sensors. I think the Optec one was designed to make telescope imaging usable on full-frame cameras... and it's only a 25% focal reduction.

pix2pixels
11-04-2010, 08:42 AM
And they are expensive: $1250.
I tried to contact Steven Mogg (http://moggadapters.com/astro/adapter.asp) again, hopefully with some success.

tonpole
11-06-2010, 01:02 AM
Why would anyone want this after looking at hopeless's pictures?

mojo43
11-06-2010, 06:27 AM
Why would anyone want this after looking at hopeless's pictures?

Seriously, I don't get it?

hopeless_4ever
11-06-2010, 08:15 AM
You really have to read the whole thread to "get it" or understand what this is about. All of this is just an experiment to prove that it's POSSIBLE to use a focal reducer on a micro 4/3 camera. Actual photography results might not be great yet, but maybe someone out there can make something of better quality.

Anyway, I already asked people to hold judgement until I make a proper adapter. The pictures above were taken with the lens being held by hand, so there's all sorts of problems (focus shifts and stray light, in particular).

hopeless_4ever
11-07-2010, 10:26 AM
Hello everyone! Just like I promised, I finished my m4/3 focal reducer adapter. This is how it looks like:


http://img176.imageshack.us/img176/5469/m43reduceradapter.jpg


It fits my E-P1 like a glove to a hand! I calibrated it for infinity focus with Nikon lenses (actually, it goes past infinity, but only slightly). Image quality is *MUCH* better than before. No blur, no tilt/shift effects, no stray light pollution. Lens speed is increased, and it's pretty sharp for what it is, although contrast is slightly decreased. Here's a test I did last night... it was shot at ISO800 to avoid blur from my handshake, but I'll have some low-ISO shots soon for you guys:



ROKINON FISHEYE 8/3.5 NO REDUCER:

http://img811.imageshack.us/img811/5167/ep1noreducer.jpg
OLYMPUS E-P1, F3.5, P MODE, -1.7 EV, ISO 800, 1/13 sec




ROKINON FISHEYE 8/3.5 WITH 0.6x REDUCER:

http://img577.imageshack.us/img577/6434/ep1reducer.jpg
OLYMPUS E-P1, F3.5, P MODE, -1.7 EV, ISO 800, 1/25 sec


LINKS TO FULL SIZE IMAGES:
NO REDUCER: http://lh5.ggpht.com/_vO7nk0ZUy_k/TNbqYZuB0pI/AAAAAAAAABI/YdiQWXUnrsI/ep1-no-reducer.jpg
WITH REDUCER: http://lh3.ggpht.com/_vO7nk0ZUy_k/TNbqY7Jd0bI/AAAAAAAAABM/4po-S2Ohb0M/ep1-reducer.jpg

The vignetting seen above is not from the reducer but the lens. The fisheye lens is DX format, made for Nikon's APS-C, so it creates a smaller circle than a lens designed for a full-frame would. If you remember from my previous post, there was a dark edge around the frame caused by the lens hood; I shaved off the hood to get more coverage for this test.

Here is a vignette test for this fisheye with the reducer: http://img822.imageshack.us/img822/5453/ep1reducerfisheyevignet.jpg
And here is a test with the same lens on full-frame (Canon 5D) and APS-H (Canon 1D) cameras: http://www.360pano.de/en/samyang_5D_1D.html

As you can see, the lens coverage with the 0.6x reducer is somewhere between APS-C and Canon's APS-H. This means that some of Nikon's DX lenses will vignette with this reducer.

I will provide more sample images soon :happy:

tonpole
11-07-2010, 04:36 PM
The extra fov isnt something you could use anyways, even if it was sharp, the distortion is too much, but maybe thats just your fisheye.

bwwd
11-08-2010, 06:34 AM
To widen FOV if you dont like crop factor of GH1 you can do yourself full frame FOV (with for example 50mm lens) so it will be like on 5D.You need biconvex lens on the rear of 50mm lens and move lens closer to the sensor, OR you need plano concave lens in front of the 50mm lens and move lens a bit away from the sensor.
I wouldnt do that on telephoto lenses tho cause sides are blurred ,but it depends of course on size of your biconvex or plano concave lens,it should match your prime lens so you would avoid chromatic aberration and softness.
You arent gaining light IMO, you also have deeper focus after this conversion and its not that shallow anymore,kinda like 35mm lens maybe a bit shallower if your 50mm is 1.8.

Psyco
11-09-2010, 09:44 AM
Does anybody know about an anamorphic focal reducer? Or an anamorphic lens small enough to be used between lens an sensor?

I ordered this (http://cgi.ebay.de/ws/eBayISAPI.dll?ViewItem&rt=nc&nma=true&item=110591985528&si=PTsd%252FVfnba1A97hCc%252F%252FnT3JZwPU%253D&viewitem=&sspagename=STRK%3AMEWNX%3AIT#ht_1522wt_907) x0.5 focal reducer with 2" diameter on Ebay - but shipping form the US will take 2-3 weeks :-(

Hopefully I will get something like hopeless_4ever together - looks pretty good. An additional test with a normal lens would be great hopless... ;-)

Cheers

hopeless_4ever
11-09-2010, 01:12 PM
I ordered this (http://cgi.ebay.de/ws/eBayISAPI.dll?ViewItem&rt=nc&nma=true&item=110591985528&si=PTsd%252FVfnba1A97hCc%252F%252FnT3JZwPU%253D&viewitem=&sspagename=STRK%3AMEWNX%3AIT#ht_1522wt_907) x0.5 focal reducer with 2" diameter on Ebay

I just ordered the same one last night, but for 1.25" instead of 2". My Vixen reducer is 1.25", so I decided to stay with that diameter as it seems to work well for micro 4/3 sensors. With your reducer, however, you *might* have to increase the distance from the sensor because I think 2" is made for SLRs with bigger sensors and longer flange distances, instead of CCD cameras. I might be wrong though! I went with Antares because I've read that it's pretty good quality, sharp edge-to-edge, and holds good contrast... and because it's 0.5x versus the 0.6x I currently have, so I want to see if I can get even more lens coverage.

This would be interesting if both of us could compare which reducer size works better for micro 4/3. Right now, I seem to be only one experimenting with this, so welcome to the club! :cheesy:

As for testing a normal lens, I really don't have any... The only other Nikon lenses I have besides the fisheye are: Nikkor 105/2.5, Sigma 30/1.4, Nikkor 43-86mm F3.5, and Nikkor 28/3.5. I've tried my friend's Nikkor 50/1.4D briefly and, while the reducer produces a wider image, it doesn't increase lens speed. The reducer only makes slow lenses faster. I think that the cutoff is around F2 or so... When I use my Sigma 30/1.4 lens, for example, the reducer widens coverage but the lens speed is the same, and optical quality is degraded. My sharp and contrasty Sigma 30/1.4, for example, turns into a dreamy soft-focus lens. I wish I could compare directly, but I think that the Nikkor 50/1.4 was sharper and held more contrast, so focal length might be a factor as well, 30mm versus 50mm. I don't think it's a good idea to use it on fast wide lenses...

Psyco
11-20-2010, 09:32 AM
My reducer still isn't here - aaarrghhhh!

I bought the 2" version, because normally lenses give the best picture from the centre part - with normal full frame lenses you don't need the 2", but maybe it just works a bit better.


I don't think it's a good idea to use it on fast wide lenses...

I really hope you are wrong on that part.

Thats the whole purpose for me: I need a wide and fast lens for my GH13!

At the moment I just can't afford the pancake 1.7/20 or a Tokina 2.8/11-16, but I have nice old Minolta glas right here: Rokkor 1.4/50, Rokkor 1.8/35 and Kiron 2.0/24. If I could just use these lenses with there full frame FOV, I would be vary happy.

We will see - hopefully my focal reducer arrives next week...

pix2pixels
11-20-2010, 10:34 PM
Do not discount some of the wide angle adapters that can be attached at the front. Some of them deliver very good results, though there is no luminosity gain.

Psyco
11-21-2010, 12:22 AM
I have them all ;-)

At the moment I have some wide angle converters here to test:

- Raynox 0.66
- Tecpro 0.65s
- Century Precision Optics 0.65

These are the widest rectilinear (non-fisheye) converters out there.

All of them show rather bad distortion in picture corners if I use a fast lens (like 1.4/50 or 2.0/24).
It would be plan B for me, but if I can avoid an extra 500g in front of my lenses (they also weight about 400g), it would make things easyer.

j
11-21-2010, 09:31 AM
You lump the Century in with the Raynox?

I find it to be quite good by comparison. (although nothing like clean glass without an adapter in front...)

hazilo
11-23-2010, 01:16 PM
Does anybody want to try this one: http://cgi.ebay.ch/Telescopes-1-25-inch-0-5x-Focal-Reducer-Metal-/280385585515?pt=LH_DefaultDomain_0&hash=item414848816b
It's damn cheap, and I guess 1.25" is enough for m4/3 but I might be wrong...
I will order it and try to make something good with it combined with my m42 adapter!

joe1946
11-28-2010, 06:00 PM
I use a Celestron F6.3 Focal Reducer with my C9.25 , C6 XLT and Apex 127 5" Mak scopes to shoot HD video with my Pentax K-7 and plan on getting the GH2. I am sure I will be having fun with it since the video quality will be much better. Here is a photo of my F6.3 FR on my C9.25 that has a 2350mm FL @ F10 and 1480mm @F6.3.
26290


http://www.youtube.com/watch?v=UJcI2uDOMCc

http://i8.photobucket.com/albums/a21/jogiba/my%20K-7/IMGP2366.jpg



http://www.youtube.com/watch?v=l4L_ZKCA3DI

http://i8.photobucket.com/albums/a21/jogiba/my%20K-7/IMGP2385-1.jpg


http://www.youtube.com/watch?v=FqlnRDq9kDI

NURBS
11-28-2010, 11:47 PM
Does anybody want to try this one: http://cgi.ebay.ch/Telescopes-1-25-inch-0-5x-Focal-Reducer-Metal-/280385585515?pt=LH_DefaultDomain_0&hash=item414848816b
It's damn cheap, and I guess 1.25" is enough for m4/3 but I might be wrong...
I will order it and try to make something good with it combined with my m42 adapter!

It's poor quality reducer, I'm have it, not recommended.

Psyco
12-27-2010, 01:20 PM
So, I finally got my focal reducer: Antares 0.5x 2"

The lens of the reducer is about 40mm wide, to not be the limit for the nearly 30mm wide back lens of the Rokkor.

- GH13 ;-)
- Antares 0.5x 2" focal reducer
- Minolta MD Rokkor-X 50mm f1:1.4
- (cheap) C-mount to m4/3 adapter
- metall housing (was 2x Tele Converter)

27531

Left part shows the final setup (the Lumix lens is only holding all in place - while taking the actual pictures everthing was hold in place by sticky tape).


First, two pictures without the focal reducer, only the Rokkor with a proper MD/MC to m4/3 adapter - sorry for the boring subject ;-)

EDIT: The images I can post here are very small - not enough to see much difference. How can I post bigger images?

Rokkor @ f1.4, 1/80s:
27527

Rokkor @ high f-stop, 1.3s:
27529

Now with the reducer - all pictures taken in automatic exposure mode.

Rokkor @ f1.4, 1/100 WITH focal reducer:
27526

Rokkor @ medium f-stop, 1/25 WITH focal reducer:
27528

Rokkor @ high f-stop, 1.3s WITH focal reducer:
27530

I can't remember the exact f-stop (medium/high), but it was just enough to take a picture with no extra light.


Results with focal reducer:

1) the FOV gets wider by about 20%
2) the image gets brighter by about 25%
3) the image quality is reduced with low f-stops

The good news:

It works - sort of...


The bad news:

The FOV is only about 20% wider than before - not enough to count for the reduced image quality. It is possible to get a sharp image, when stoping down, but the gain in brightness doesn't compensate for that.

With the aperture wide open, the image gehts sharp but everthing gets a bright white aura.

Any ideas to improve the picture quality with low f-stops? Otherwise I will drop the idea and by a Lumix 20mm Pancake :(

hopeless_4ever
02-03-2011, 02:13 AM
Apologies for being AWOL.

Psyco, that was a fascinating experiment! Your experience with F1.4 lenses matches my own.

Here is what I realized... There is more than one possible configuration with these reducers. The setup can be done in two ways:
1) Bring the reducer closest to the sensor. Then, adjust distance to the lens accordingly for focus.
2) Bring the reducer closest to the lens. Then, adjust the distance to sensor accordingly for focus.

#1 yields better quality/contrast at the expense of FOV (less wide, less coma).
#2 yields bigger FOV at the expense of contrast (more wide, more coma).

At the heart of all this is the reducer's diameter. Psyco, you are correct to say that (in theory) wider reducers yield better images because you get more of the center portion of the image. By better, I mean less vignetting and less distortion, but not necessarily sharper.

I bought the Antares 1.25" 0.5x focal reducer and struggled a bit more to get the same FOV (field of view) as with my Vixen C-mount 0.6x (I succeeded using configuration #2). I later learned from browsing an astronomy forum that the Antares reducer is not a true 0.5x, but more like 0.6x, so it makes sense that it matched the Vixen. By the way, the Antares was not even close to being as sharp as the Vixen. With Vixen, I didn't feel that I lost any sharpness, just a little contrast. With the Antares, I had okay contrast but less sharpness. The "glow" that you are referring to is called "saggital coma flare", or simply "coma", and it is annoying. It is present to some degree in ALL fast lenses, except for one: The Noct NIKKOR 58mm f1.2 lens.

http://imaging.nikon.com/products/imaging/technology/nikkor/n16_e.htm

That's a little bit of history for you. Nikon designed that lens specifically to battle coma. VERY expensive lens. In fact, it's legendary!

So, we have 2 problems:
1) How can we increase FOV to get true "full frame" focal length?
2) How do we get rid of the glow?

Here are some possible solutions:
1) The light travels through a focal reducer in shape of a cone. The larger the reducer's diameter, the less focal reduction we'll receive on our m4/3 sensors. We need a WIDE focal reducer, with FASTER speed. I got very close with my Vixen 1.25" reducer (almost APS-H coverage but not full frame). You chose a 2" reducer and got even less coverage than I did! That means that we need something like a 2" 0.3x focal reducer to get full frame! Both Optec and Meade make 0.33x reducers for SCT Schmidt–Cassegrain telescopes (SCT). The Meade is *much* cheaper option though. The problem with those SCT reducers is that they are optically resigned to provide a flatter field, correcting distortion on the telescopes that they were designed for. I cannot find an uncorrected reducer with that speed.
2) Larger reducers generate less coma. There is always least coma in the center, and the most on the edges or in the periphery of the focal field. Just as I said in #1, we need a larger reducer. Another solution is to attach a coma corrector like this one: http://www.optcorp.com/product.aspx?pid=10026

I'm actually planning on trying both (as soon as I find a suitable reducer for #1)!

Finally, one last note. I mentioned before that fast lenses will not be any faster. Olympus made 4/3 lenses with focal reducers, but they were always choked at F2. That seems to be the limit with focal reducers. An f4 lens becomes f2, but f1.4 stays f1.4 (with decreased quality). I just want a 50/1.4 to be a 50/1.4, with the same FOV, same speed, and same quality. Is it possible? Who knows! But I also wouldn't mind having a cheap way to make any zoom lens f2! You win some, you lose some. At least we'll know what's possible :)

Brian@202020
02-05-2011, 09:54 PM
Any more experimenting or head way on this?

Psyco
02-20-2011, 09:55 AM
Hi hopeless_4_ever,

thanks for all this information. Interesting stuff about this "coma".

You are right, a 2" 0.3 (or even 0.25?) focal reducer would be a good point for further testing. Where did you find one?

What kind of distortion correction does this 0.3 reducers do? Will it really distort our images that much - or is it to minor to see with the naked eye?

The coma corrector is no option, as we don't have enough space for another piece of glass between the lens and the sensor.


Finally, one last note. I mentioned before that fast lenses will not be any faster. Olympus made 4/3 lenses with focal reducers, but they were always choked at F2. That seems to be the limit with focal reducers. An f4 lens becomes f2, but f1.4 stays f1.4 (with decreased quality).
I thinks thats not correct. Maybe Olympus limited there lenses at f2 to preserve image quality. My own test showed an increase in light with the reducer even at f1.4. It was what I expected it to be, when getting a 20% wider FOV. But to get this, you need a focal reducer big enough to catch all the light from the lens and the rear glass element of a f1.4 lens is huge!

It is interesting what you mention about Olypmus. So it looks like its possible to design focal reducers exactly for what we have in mind. Good news!
My dream would still be an anamorphic focal reducer (squeeze factor 1.5x) - that would be a must have tool ;-)

Hmmm, why has no company developed some kind of adapter with a focal reducer in it? They would make a lot of money with the success of the GH1, GH2 and AG-AF100 and all this 35mm glass out there.

So, the next part of the test program would be to find a focal reducer with stronger light bending (0.3 or 0.25) and try if we still be able to focus.
After that, we are back at the problem ob coma... (what does a coma corrector do?).

Cheers

bitcrusher
03-22-2011, 11:14 PM
Decided to try an experiment. Took out the rear lens group of a broken Tokina FD zoom lens and stuck it backwards in a FED INDUSTAR-61 55mm F2.8. The idea was to use the backwards lens group as a focal reducer. Changing the FED to a wider lens and giving me a faster f stop.

It works but the IQ derogation is extreme. Still a lot of fun to use.

http://vimeo.com/21380855

http://vimeo.com/21380713

Brian@202020
09-27-2011, 08:47 AM
I like this topic and come back from time to time to see if there is any progress. Is there anything new? or does anyone else have any experiments pending?

ape
10-10-2011, 04:04 PM
Have you guys seen this? http://www.43rumors.com/ft3-olympus-patent-rumors-adapter-with-integrated-wide-lens-and-adapter-with-swd-auto-focus/ I hope it eventually comes out, I can't afford these $700 wide angle lenses :(