C-Mount lens: the hunt begins anew

commanderspike

commanderspike

Carbonite Member
I'd like to start the C Mount lens topic again, since there are some very interesting deals out there to be hunted down. They give an incredible image for the price.

Apparently, the adapter for the G1/GH1 will accept a C Mount lens with a maximum 37mm diameter. I don't know the ins and out on how this works, can someone fill in the gaps in my knowledge?

Would this fit?

http://cgi.ebay.co.uk/COSMICAR-12-5...7f70d1&_trksid=p3286.m63.l1177#ht_2287wt_1167

What intreages me about these 16mm C Mount TV lenses is the ultra wide angle combined with very fast speed, often as bright as F1.1! And of course - the price.

Now with a 35mm full frame sensor, it would not be possible to get an acceptable picture from such a small lens, but with the Micro 4/3rds sensor being a pretty good match to 16mm film, you still get a bit of light fall off at the edges but in 16:9 mode it works pretty well.

I also find these lenses have very interesting bokeh.

zeiss_g1_sample3
 
I don't have any yet :)

I have the Zeiss & Canon FD 35mm lenses, but I want to choose a TV lens based on the following attributes:

- As little vignetting / fall off as possible on the GH1 in 16:9, but a little bit is acceptable and actually an effect I quite like. What I want to avoid is the full 'peep-hole' effect with a dark black circle from top to bottom.

- As wide as possible... 8-16mm and lots of nice radial bokeh.

- As fast as possible. F1.4 or under.

- As cheap as can be.
 
I have a c-mount adapter for my GH1. I bought one of the Cosmicar 12.5 mm for about $40. Be advised the back of the lens has to be filed down for it to fit into the c-mount adapter, otherwise it doesn't screw in far enough to focus the image. There's a tutorial online somewhere on how to do this. Maybe check flickr.com and search under c-mount.

I have acquired several lenses. In general, I have found that the wide-angle lenses (8mm-15mm) all have the peep-hole vignetting you speak of. The image is just a circle in the middle of a black screen. The effect is more pronounced the more you close the iris. TV lenses seem to be even worse as far as the vignetting with wide angles. However, I love using these lenses! They are inexpensive, and very fast. The ones I'm using (Switar lenses) were for an old Bolex 16mm camera, and the image quality seems great to me. I don't mind the vignetting for certain projects. Of course, for regular dramatic projects, it would be a little weird. So, my search is still on for a fast wide-angle lens.

You can see something I shot with a 25mm Switar here:

http://www.vimeo.com/5626742
 
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Thanks for that. I enjoyed your boxing video. The vignetting is very mild in that. Do the 8mm / 15mm wide lenses vignette all the way around in 16:9, with even the top and bottom of the circle visible? :violin:

Do ALL c-mount lenses have to be filed down to focus? That's one thing I REALLY want to avoid.
 
commanderspike said:
What intreages me about these 16mm C Mount TV lenses is the ultra wide angle combined with very fast speed, often as bright as F1.1!
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It is the ultra wide angle lenses that won't work without massive, massive vignetting. Peephole effect.

Lenses about 35mm or longer will usually work; shorter than 25mm and you will always get vignetting.

but with the Micro 4/3rds sensor being a pretty good match to 16mm film
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??? The Micro 4/3 sensor is about 3x as large as 16mm film!
 
commanderspike said:
Do the 8mm / 15mm wide lenses vignette all the way around in 16:9, with even the top and bottom of the circle visible? :violin:
Click to expand...
Of course.

Do ALL c-mount lenses have to be filed down to focus? That's one thing I REALLY want to avoid.
Click to expand...
No, but that's what the 37mm diameter was referring to. C-mount lenses have to sink into the adapter, and if they're too wide around they won't "sink in". If it's really close you could probably file 'em I guess.
 
I dug up some info on another forum from a guy who'd used a Schneider 10mm/f1.8 C Mount Cine Lens on his G1 (this was before the GH1 came out)

169crop-vi.jpg


720in1080-vi.jpg


He was able to get decent 720p coverage from a 1080p frame. The whole picture represents the lens coverage over the whole of the G1's sensor. Bare in mind that the 16:9 mode on the GH1 is slightly larger? Well... slightly higher res anyway?

A very fast 25mm has almost full coverage, no need to crop. Works pretty nicely for the price, I think. :shocked:

Maybe I'll avoid the idea of getting a wide C mount lens and go for a ultra fast portrait style lens. F0.9 anyone? :)
 
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Barry_Green said:
The Micro 4/3 sensor is about 3x as large as 16mm film!
Click to expand...

Sorry! My bad... I thought 16mm was just under half the size of 35mm. I don't know much about classic photography formats. And of course, Micro 4/3rds is four thirds the size of 35mm I take it :)

I found this c-mount lens G1 / GH1 compatibility list:

http://spreadsheets.google.com/pub?key=p9kkgjwEQQQ-HJwvNDobeEw

Some great info and sample photos on this thread: http://forum.getdpi.com/forum/showthread.php?t=6025&page=2
 
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16mm = about 10mm x 7.5mm, for 75 square mm.

4/3 = about 18 x 13.5mm, for about 243 square mm. That's over 3x as large as 16mm.

35mm cine = about 22mm x 12mm (at the 1.85:1 aspect ratio), for 264 square mm.

(That makes it sound like 4/3 or Micro 4/3 sensor is the same-ish size as 35mm movie film, and that's not a fair comparison because the aspect ratios are different. When cropped to 1.85, M/43 would be 18x10, or 180 square mm.)

35mm still film = 36x24mm. That's twice as wide as Micro 4/3, and about 1.8x as tall, for an overall size of 864 square mm. Much larger than M4/3 or cinema film.
 
cinelenscoverage.jpg


Thanks Barry. The diagram above also clears this up and basically anything on the chart (end of page 1) which has coverage for over 20mm frame size diameter will be suitable for the GH1.

Now I just need to hunt them down... eBay has gone mysteriously quiet for c-mounts at the moment.
 
That chart's a little bizarre... S16 is no taller than 16mm, they're the exact same height, but S16 is a little over 2mm wider.

And don't think that a 20mm lens will automatically cover. Some might, some won't. In this thread I discuss my findings and others chip in; "upshot" shows a non-vignetting shot from a Schneider 16mm, whereas a 26mm Switar shows noticeable vignetting.

I think you're pretty safe from 35mm on up, but below that you'll have to verify with each and every lens you intend to consider.
 
Barry_Green said:
I think you're pretty safe from 35mm on up, but below that you'll have to verify with each and every lens you intend to consider.
Click to expand...

You are correct, but thankfully this database has been created: http://spreadsheets.google.com/pub?key=p9kkgjwEQQQ-HJwvNDobeEw

They measured the coverage circle of each lens on the list, with it's suitability for the M4/3rds format in mind.

Then there is the Canon 50mm F0.95 TV lens. Anybody have one of those hidden behind the sofa?
 
zeiss 25mm 1.4

zeiss 25mm 1.4

I have the zeiss tevidon 25mm 1.4 from the first page. Really interesting image, major vignetting but depending on the circumstance that can be a positive, not a negative.

Won't be using it all the time, but will be happily using it for stylized shots. Also - with the lens attached to my GH1, the whole package can fit in a large jacket pocket.

Attached a frame grab from some 1080p24 I shot.
 

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Navitar, 25mm f0.95 or 50mm f0.95

Navitar, 25mm f0.95 or 50mm f0.95

I am a bit worried that the 50mm will be a bit to close for general picture taking. I really like a 50mm equiv or better a 35mm equiv with all the speed. I had my Leica stolen and the 50mm f2 summicron and 35 f 1.2 stolen as well. How bad is the vinetting on the navitar 25? I have looked and seen some reference to M1 and M2, but does anyone have actual pictures taken form a navitar 25mm f0.95 do2595 that they can send me a link to or post?

Thanks!
 
Would the guy on ebay buying all the c-mount lenses please stop!! :D

Its been so hard to come up with any bargains. I did however find this cool dude...

xenonf2.jpg


http://cgi.ebay.co.uk/ws/eBayISAPI....163486&ssPageName=STRK:MEWAX:IT#ht_500wt_1182

The seller says it's ex-military (British), and it's by the well known German lens manufacturer Schneider (which currently has a deal to make lenses for Samsung and Pentax). German lens maker helping British war efforts - ironic.

1.6cm is 16mm - but I think this is a guess by the seller (he said he'd shone a bright light through the lens and measured the image circle) as the condition of lens means the true focal length has been erased from the front by wear and tear. I found a guy on Flickr using the a 16mm Xenon F2 on a G1 and it doesn't cover the whole sensor but I like the effect. Image quality seems pretty nice for £20. I am not sure if it has the amazing bokeh I have seen on other C-Mount lenses. The pics I have found from this one guy on Flickr are all just snap shots of a trip.

xenonf2sample.jpg


I also found another lens, not a c-mount though...

Cooke Speed Panchro 35mm f2

Someone may have got a bargain here. But I am not sure if PL / Arri mount lens can be fitted to the GH1 and at what cost so I was wary of bidding as it passed the £70 mark. Pretty sure they can but know nothing about it yet so treading cautiously.
 
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Thanks. A little more expensive than the usual adapters, but probably worth it knowing how good the Panchro lenses are.

For now though, sticking to c-mounts. I'll do a video with the Xenon and post later.
 
what c mount adapter are you using/plan using? ive seen the thin ones like JR and some that appear slightly thicker to the human eye. not sure which one to get.

and yes, i too think there is a c-mount fiend lurking on ebay...ha
 
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