Turning GH1 into a full frame sensor with FD lenses

[commanderspike]

I just found something interesting, which maybe has a lot of potential... it could allow us to use the full 35mm equivalent focal length of our Canon FD lenses.

I backed my Canon FD 50mm F1.4 onto a macro lens - a thin glass plate that screwed onto the back of my el-cheapo 0.45x video lens wide converter.

I placed the combination (held together with my hand!) to the back of the GH1. At the correct distance - much closer to the sensor than the FD adapter allows, I appear to be getting the full 35mm image circle appear on the LCD.

The macro glass is either acting as an optical reducer, or allowing the GH1's sensor to pick up on the image from the lens a lot closer to the sensor, so that the image circle is reduced but can still be focussed.

I can focus to infinity.

Interestingly, moving the combination of macro glass and lens further out to where the FD adapter places the lens gives the lens stunning macro performance at F1.4... but is is then useless for infinity focus.

I hope someone with the right machining tools and know-how can pick up on this macro glass insert and make an FD adapter with it. All it needs is a good seal to the body, the right distance from the sensor and the right macro glass. There is no reduction in image quality or brightness either - just an expanded field of view.

[Ian-T]

Wow...amazing. It makes a lot of sense when I think about it. How about light loss??

[PhilD]

Dear Commander,

I have forwarded your message to ciecio7 who sells FD adapters on eBay.

I wonder if a temporary solution would be to use clear filters, the FD adapter and step down/up rings. I have a macro lens that came with a wide adapter but it's much too small, I used it for my FZ50

[DanDOF]

Good job Commanderspike,
You and others already know about the Focal Reducer thread but I'm just going to link these threads for easy reference:



Focal Reducers - Squeeze all your FOV and Light on your GH1 Sensor (http://www.dvxuser.com/V6/showthread.php?t=170446&page=5)
Canon FD adapters (http://www.dvxuser.com/V6/showthread.php?t=178471)
ciecio7 ebay seller and adapter manufacturer (http://myworld.ebay.com/ciecio7)


A few months ago I began looking at how to invent this, drawing lots of diagrams with my pencil and researching websites. The fact is, at this point, I don't have the practical knowledge or equipment necessary to manufacture this great idea of a product.

Good luck to whomever wins that prize of being the first.

[Ben_B]

Cool. I'll take one for Nikon! I'm sure there must be some kind of light/quality/sharpness loss associated with manipulating the optics in this way...also did you say you had to hold the whole thing right on the camera? close than the adapter allowed?

My camera turns off the sensor when lenses are off the camera, even when shoot w/o lens is on...only way I can see things sans lens is when it still thinks a lens is on because my adapter is still on. Hmmm.

[commanderspike]

No light loss from what I can see so far. Maybe a tiny bit of sharpness lost on the edges of the frame, but this is a VERY cheap piece of macro glass.

Pics to follow.

Yes Ben... indeed the macro glass and FD lens need to be held closer to the sensor than the FD adapter allows. This isn't a problem for whoever manufacturers this. They just need to make a thinner mount adapter which also doubles as macro glass.

I hold the macro glass flush with the GH1's mount and the lens slightly (5mm?) away from the macro glass to get perfect focus.

I hope I can find out what the spec of the macro glass is - it has no markings, no manufacturer - nothing! To repeat this and make it mass produced would need a supply of good quality macro glass.

[commanderspike]

Update... a little more about how this works.

Usually the lens would be mounted quite far from the sensor, to mimic the flange back distance of the 35mm camera it was designed for.

The distance of the lens to the sensor directly influences the size of it's projected image circle onto the sensor.

So on a normal FD adapter:

Sensor |---------------adapter--------------( lens

By adding the macro glass, this magnifies the view of the back of the lens that the sensor sees, allowing you to mount it closer to the sensor, thus reducing the image circle. (If I understand it correctly.... not 100% sure... please correct this theory if you see any holes in it).

Sensor |--( macro ----( lens

The macro glass acts as a magnifier. The lens backs onto the magnifier at a short distance.

The trick also works with a Contax Zeiss lens, so is repeatable for any type of 35mm lens adapter. Whoever has the tools to create this adapter is going to be very rich.

Some very quick snaps:

With macro glass & short flange back distance:

http://www.brawnf1blog.com/GH1/fflens1.JPG

With standard FD mount adapter (2x crop factor):
http://www.brawnf1blog.com/GH1/fflens2.JPG

Please note that I simply held on (with my bare hands!!) the macro glass and Canon 50mm lens to the GH1's body. The image extends to the left because I had to avoid pressing in the metal pin on the GH1's mount which blanks the screen unless there is a proper lens locking mechanism attached to the mount. But the lens is pretty much flush to the body, there is about 5mm or 7mm between the mount and the lens plus 10mm for the macro glass - plenty of room to build the adapter casing and mount locking mechanism.

[PhilD]

ciecio7's answer:

Hello

It might seem real but there will be some disadvantages:

- the image would have distortion, especially edge of frame
- quality of image would deteriorate
- it would appear problems with focusing

I think it should be adapter with a few lenses so the price would be quite high.


Regards

Ryszard

[commanderspike]

ciecio7's answer:

Hello

It might seem real but there will be some disadvantages:

- the image would have distortion, especially edge of frame
- quality of image would deteriorate
- it would appear problems with focusing

I think it should be adapter with a few lenses so the price would be quite high.


Regards

Ryszard


Thank's Phil for sending the info to Ciecio

For 50mm lenses the image drop off at the edges is minimal but I found with 28mm lenses the image drop off at the edge is very dramatic.

But it bears repeating that the macro glass I'm using is too small for a 28mm lens and is of very very low quality.

I'd happily pay £150+ for such an adapter... maybe more if it was a good one. As you can see from above, the 50mm image quality is perfectly acceptable and I was holding the make-shift construction almost askew to the GH1 with my own shaky hand!!

[Ben_B]

I see some problems with that first image hate to say..look at the edge of like where the black sweatshirt is hanging..some weird stuff going on with the focus there...more so than just soft focus.

[PhilD]

As I said earlier I also had a similar adapter for my FZ50 but it was also of very low quality, it came with a 100$ starter kit I bought on eBay. Made by a company called "DIGITAL".

[commanderspike]

I see some problems with that first image hate to say..look at the edge of like where the black sweatshirt is hanging..some weird stuff going on with the focus there...more so than just soft focus.

Yep but the centre is pin sharp and there is no loss of light.

The odd effects are due to a combination of the poor quality macro glass and me holding it slightly skewed to the lens body when it should be perfectly flat.

The theory is right - it works - just need to find the right quality of macro glass at the right magnification and at the right diameter.

[Kholi]

Commander already stated that it's cheap macro glass, and we don't know how the lenses that he's using perform at the corners and edges anyway. So, those must be accounted for in considering the validity of the test.

I think it's completely valid and quite awesome. If someone can make an adapter that'll still allow proper registration distance for all lenses, then it'd be a no brainer to pick one up and use it on and off as you see fit.

Nice.

[Ben_B]

How about gaff taping it? :)

[commanderspike]

How about gaff taping it? :)

No problem :) But the issue is the GH1's mount - there isn't yet an adapter thin enough to mount my gaffer taped FD lens and macro glass onto the GH1 so it's close enough to the sensor. But that's only because the FD adapter is HUUUUGE.

Early days yet. Will try and get hold of a range of macro glass and see what the effects are. It does seem to be a good 1.1x crop factor which results... almost full frame if not even the full 1.0x. Just need to work on the mount and macro glass.

[JJ_HomeFri]

Mr. commander spike,

If you have any diagrams, feel free to send them my way and I will apply for a U.S. patent for you. i will only take 10%* of any and all moneys you receive from your invention. PM me if you are interested.


-Jared G.





*multiplied by 10

[yslee]

Doesn't look good. Also there appears to be significant loss of DOF.

[Ian-T]

He had it at infinity

[Nighthawk]

Yeah, I'm more than willing to take commander at his word. Despite some edge definition problems and a few other issues the dude was just holding the lens and glass in place by hand. No doubt the crop factor issue and FOV is easily workable with a properly designed and machined adapter. Somebody out there go for it and you'll make some dough especially if the 4/3s market grows and for God's sake pay commander what he'd be owed. He seems the type that would buy us all a beer if that happens and I'm thirsty constantly.

[brianwu]

Yes it will work, actuary I was doing the same thing all week at work (and not doing my work :Drogar-Shock(DBG):). There are 2 problems for me so far, first the add on optic have to move in and out with lens, so fixed mount inside the adapter likely will not work or won't work well (focusing), luckily I have some optic (http://www.edmundoptics.com/onlinecatalog/displayproduct.cfm?productID=2911) at work that I can try on. For now I just taped on to back of the stock lens. Another way to do is (witch I might do it) disassemble the stock lens and replace the last optical element to higher power one (same as add another optic ) ..Uh and clean all other glasses if I don't screw up:violent5: and I'll have M4/3 specific lens.
Second problem is after modification all the adapter on the market will not work so I guess I 'll have to make them my self, witch still kind easy, just buy a C mount adapter and a old camera (for your lens, if you have a Canon get a A-1 or AE-1 etc.. all you need is that lens mounting plate) from Ebay I got M42 mount myself, it is much easy to work on.
Still experiment all possible way, nothing is for sure but up to now I do think it will work. Now back to building my 16 hr. battery pack:happy:

[Ben_B]

No problem :) But the issue is the GH1's mount - there isn't yet an adapter thin enough to mount my gaffer taped FD lens and macro glass onto the GH1 so it's close enough to the sensor. But that's only because the FD adapter is HUUUUGE.

Early days yet. Will try and get hold of a range of macro glass and see what the effects are. It does seem to be a good 1.1x crop factor which results... almost full frame if not even the full 1.0x. Just need to work on the mount and macro glass.

Actually I meant gaff taping the whole shebang to the camera :D