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Using odd lenses on Micro 4/3rds cameras
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PostPosted: Thu Nov 19, 2009 8:04 am    Post subject: Reply with quote
A bit late to the party, but here is another dizzying Cooke Kinic 25/1.5 shot with the G1, fully open. This is the older uncoated version. I love this lens.

BTW, Sebastien, I love the b&w shots with the old Leica lenses. I was born in Wetzlar where the original company seat was and half my family worked for Leitz/Leica at some time or another, I would love to get my hands on some of the old lenses.

Stefan



PostPosted: Thu Nov 19, 2009 5:12 pm    Post subject: Reply with quote
Very nice shot. I wonder but never seen explained, What causes the effect of a swirley bokeh?


PostPosted: Fri Nov 20, 2009 12:40 am    Post subject: Reply with quote
JerryMK wrote:
Very nice shot. I wonder but never seen explained, What causes the effect of a swirley bokeh?

The swirls are caused primarily by uncorrected astigmatism. Petzval lenses are famous for that. Many fast Double Gauss lenses also exhibit the swirly bokeh. Optical vignetting (the cat's eye shaped highlights near the borders of the frame) also increases the effect.

Cheers!

Abbazz


PostPosted: Sun Nov 22, 2009 1:28 am    Post subject: Reply with quote
I just got a PM from user rbelyell asking a few questions about C-mount lenses. As I think the answer may be of interest to others, I'd better post it here. This way, the whole MFLenses community may also be able to contribute or to correct any error in my post.

rbelyell wrote:
as you know the x2 crop factor wreaks havoc with the lens collection. to take advantage both of ep2 low light capabiity and small form factor i want to get a fast small not expensive lens that is sharp as well. i thought c mount lenses might fit the bill, but i know even less about them than about m42. i have come across some inexpensive 16mm 1.3 comsicar lenses, also javelin, vicor and bolex.

are these good lenses? is there any thing i should look out for to accomplish what i want--for ex i notice some are labeled 1/2" format some 1" format, and i dont even know what that means.

C-mount lenses were initially used for motion picture cameras, especially in 16mm format. Now, they are still produced for video surveillance cameras (CCTV). It is important to know that a 16mm cinema image has a diagonal of 14mm, while an 1 inch video tube or sensor has a diagonal of 15.5mm (a lot less than one inch!) and a 1/2 inch sensor has a diagonal of only 8mm. On the other hand, a 4/3rds sensor has a diagonal of more than 21mm (if you want some explanations on sensor sizes, please refer to this very good page by Vincent Bockaert on DPReview).

So it is reasonable to think that almost every C-mount lens under the sun has been designed to deliver an image circle measuring less than 16mm in diameter. When we try to use it on a 4/3rds camera requiring a 22mm image circle to cover the whole sensor, then we are running into some problems: blurred edges, dark corners, or even circular image with a thick black border. These problems are much more apparent on wide angles than on long focal lenses, because the longer lenses have usually a larger image circle.

As a rule of thumb, 25mm (1") is the limit. Lenses having a focal length shorter than 25mm exhibit vignetting and edge softness, while lenses above 25mm are more or less free of these defects. As for 25mm lenses, some have dark corners while other illuminate the whole 4/3rds sensor but illuminate does not always mean cover: there is light reaching the corners of the sensor but the image can be very mushy. Usually, very fast lenses (0.95) have a worse coverage than slower lenses. This table summarizes lens coverage for many popular C-mount lenses. Every lens noted as full>22mm will at least illuminate the whole 4/3rds sensor.

To get back to your questions, I don't think a 16mm Cosmicar -- or any other C-mount lens having that focal length that I am aware of -- will cover the 4/3rds sensor. Even for 25mm -- which is by no means a wide angle on 4/3rds format -- the coverage is usually not very good and most lenses are best used for special effects only. You also have to keep in mind that many of these lenses were designed to be mounted in front of a video camera which definition doesn't exceed a few hundred lines. They are indeed very good at providing that old fashioned look, but don't expect them to outperform the kit zoom at medium range or the new Panasonic 20/1.7 lens.

I you want to buy C-mount lenses, try to avoid the current madness on eBay. I see people paying more than $500 for lenses that are unusable on a 4/3rds camera without intensive modifications because their barrel is too wide. Don't forget that some of these c-mount lenses are also available new from CCTV retailers (or from B&H), and usually for less money than they go for on eBay. Old ciné lenses are plenty and can be bought for cheap when attached to obsolete motion picture cameras. These cameras are common at garage sales and they typically sell for next to nothing.

Some good reading about C-mount lenses:
- Arthur Cox, Photographic Optics, Focal Press, London -- Mr. Cox was a lens designer working for Taylor, Taylor and Hobson and there are a few comprehensive tables at the end of the book listing most common c-mount lenses.
- Liste des 193 Objectifs monture c -- a good web site in French with lots of image samples.

Cheers!

Abbazz


PostPosted: Tue Nov 24, 2009 8:45 am    Post subject: Reply with quote
Excellent summary Sebastien! I was fortunate enough to get my hands on a larger lot of c-mount lenses, just before the prices went totally bananas, and fully agree that 25mm is the cut-off point. Some wider lenses are not bad if you crop out the center part of the picture, but, of course, then they are not really wide angles anymore... It is fun to play with these lenses if you get them for a reasonable price, but I have started reselling most of the wide ones in the meantime, planning to keep only a few that I like for their unique effects (like the Cooke Kinic) or the few that at least show good illumination (and almost coverage) and bring additional benefits, like the Angenieux M1 25/0.95. If you don't mind me linking to my own post on getdpi, I did a quick and dirty comparison between some 25mm c-mount lenses reg. sensor coverage and vignetting here: http://forum.getdpi.com/forum/showthread.php?t=8410 . Not all lenses were optimally clean and the light was awkward, but you get an idea about the usefulness. Sometimes a bit of vignetting in the corners can add to a picture IMHO, but in many cases it may be just distracting.

That said, there are some excellent longer c-mount lenses out there that make very nice, very small and very light primes. This definitely includes the Kern-Paillards. They have gone up in price quite a bit but you may still find a 75/2.8 Yvar lens for a reasonable price. I find that the Schneider c-mounts are underrated on ebay, and the 150mm and 100mm tele-xenotars are excellent lenses - a bit heavier because of the metal construction, but still small compared to other lenses of that length. The old Kodak cine lenses also have quite a bit of charme, especially the 63/2 is great on the m4/3 system (well, on my G1 at least). The 40/1.6 and the 50/1.6 cine Ektars are also nice, but the 40mm is hard to find. The 50mm even has a macro mode which supposedly works very nicely - ask me again in a few weeks when mine comes back from servicing... My overall favorite, so far, is the Kern Switar 75/1.9 macro, but I wouldn't buy it anymore for the current prices, you pay less for a Summicron 90/2 these days Shocked

Sorry, I have been spending more time shopping for lenses than taking pictures recently and my job is crazy right now, but I'll try to find a few pics to upload...

Stefan


PostPosted: Tue Nov 24, 2009 10:15 am    Post subject: Reply with quote
Well, I have just finished some tests I made with Tevidons I have here and I can confirm the findings as mentioned by Sebastien (abazz). From about 25mm focal length onwards vignetting disappears, so the full set consisting of the focal lengths 10, 16, 25, 35, 50, 70, 100mm leaves out the 10+16mm versions, due to quite some vignetting (except someone likes that effect). The 25mm is borderline, so still some vignetting is visible but just in the corners (a nice useful effect at times); this disappears if the 16:9 format is being used. From 35mm onwards all vignetting has disappeared.

Tevidons are tack sharp and contrasty lenses once made in the former GDR by Carl Zeiss Jena (later sold to DOCTER OPTICS which continued making them; and still does btw.) as video lenses to protect their border safety, massively built (the first series) and in the later second series was built much lighter. They came in c-mount (rare) and a special bajonet mount to fit their vidicons. The spectral range is 400-1000nm fully achromatically (some say apochromatically) corrected (!!), so there is no focus shift, if these lenses are being used for IR photography in the 750-1000nm spectral band.

I have now found a way to convert these bajonet mount lenses to c-mount using a newly designed precision mount to make these usable for mft (micro 4/3) cameras. More about that later.

Last edited by kds315* on Tue Nov 24, 2009 12:53 pm; edited 1 time in total


PostPosted: Tue Nov 24, 2009 12:01 pm    Post subject: Reply with quote
Klaus,

Have you tried your 18-90/2 Vario Tevidon on the GH1 as well?


PostPosted: Tue Nov 24, 2009 12:55 pm    Post subject: Reply with quote
dickb wrote:
Klaus,

Have you tried your 18-90/2 Vario Tevidon on the GH1 as well?


Not yet Dick since the mount is very different, but it appears that there will apparently be some vignetting.


PostPosted: Tue Nov 24, 2009 1:30 pm    Post subject: Reply with quote
apicius9 wrote:
Excellent summary Sebastien! I was fortunate enough to get my hands on a larger lot of c-mount lenses

You're welcome, Stefan. That glorious heap of lenses in your avatar is mouth watering...

apicius9 wrote:
Sorry, I have been spending more time shopping for lenses than taking pictures recently and my job is crazy right now, but I'll try to find a few pics to upload...

Please do !

Cheers!

Abbazz


PostPosted: Tue Nov 24, 2009 1:36 pm    Post subject: Reply with quote
kds315* wrote:
Not yet Dick since the mount is very different, but it appears that there will apparently be some vignetting.

That's what I was afraid of, Klaus. I find the C-mount zooms quite disappointing regarding coverage. But the longer Tevidon primes look very interesting, if you see what I mean ...

Cheers!

Abbazz


PostPosted: Tue Nov 24, 2009 3:14 pm    Post subject: Reply with quote
Just some TEVIDON test pics taken at ugly + nasty weather fully open shot at infinity.
Full sensor format using Lumix GH1, just resized, no cropping or sharpening or contrast
enhancement applied - straight from the cam.

f=35mm


f=50mm


f=70mm


PostPosted: Wed Nov 25, 2009 12:04 am    Post subject: Reply with quote
kds315* wrote:
Just some TEVIDON test pics taken at ugly + nasty weather fully open shot at infinity.

These pictures look very promising. The corners are not very sharp on the 35mm shot, but this has to be expected at F/1.9. Vighetting, chromatic aberrations and distortion seem to be absent. Thanks for the pictures, Klaus.

Cheers!

Abbazz


PostPosted: Wed Nov 25, 2009 3:15 am    Post subject: Reply with quote
kds315* wrote:
The 25mm is borderline, so still some vignetting is visible but just in the corners (a nice useful effect at times); this disappears if the 16:9 format is being used. From 35mm onwards all vignetting has disappeared.

When you shoot in 16:9, 3:2 or 1:1 with the E-P1 (or E-P2, Panasonic G1 or GF1 for that matter), the camera is cropping the picture, that's why you can easily hide the dark corners under the rug by choosing the 16:9 aspect ratio. It is more difficult with the GH1, because it's the only M4/3rds camera that has a constant field of view in 16:9, 3:2 and 4:3. On this particular model, the oversized sensor allows for multiple aspect ratios while retaining the angle of view (meaning the image circle remains the same). Here's a page on Panasonic's website with a nice Flash animation presenting the trick:
http://panasonic.net/avc/lumix/systemcamera/gms/gh1/high_image.html

And here's a illustration from DPReview:



Cheers!

Abbazz


PostPosted: Sat Nov 28, 2009 8:15 pm    Post subject: Reply with quote
Thanks Sebastien,

I should read manuals more I guess.... Wink Wink


PostPosted: Sun Nov 29, 2009 2:45 am    Post subject: Reply with quote
The Tevidon images seem excellent considering all the circumstances.


PostPosted: Mon Nov 30, 2009 1:46 am    Post subject: Reply with quote
Thanks so much for this thread. Wow!!!

Jules


PostPosted: Mon Nov 30, 2009 1:57 pm    Post subject: Reply with quote
lulalake wrote:
Thanks so much for this thread. Wow!!!

You're welcome, Jules.

Here are a few more pictures from the less visited areas of Bandar Seri Begawan taken with the Cooke Kinic, the wow lens which has instantly gained the rank of favorite of the moment on my E-P1, eclipsing every other lens:























Cooke Kinic slideshow: http://abbazz.zenfolio.com/p980496762/slideshow

Cheers!

Abbazz


PostPosted: Mon Nov 30, 2009 2:05 pm    Post subject: Reply with quote
Thank you for the new pictures.
The more I browse in this thread, the more do I want a Micro 4/3, too.
Might be useful as back-up body for vacaciones, too. Good excuse to get one... one day.

Klaus


PostPosted: Mon Nov 30, 2009 2:10 pm    Post subject: Reply with quote
exaklaus wrote:
Thank you for the new pictures.
The more I browse in this thread, the more do I want a Micro 4/3, too.
Might be useful as back-up body for vacaciones, too. Good excuse to get one... one day.

Thank you for the kind comments, Klaus.

You know resistance is futile Wink ...

Cheers!

Abbazz


PostPosted: Mon Nov 30, 2009 2:47 pm    Post subject: Reply with quote
Great pictures indeed, thanks Sebastien!

That Kinic indeed shines whenever somthing is right centraly located in the middle of an image
so that swirly fuzzyness enhances that; with landscape shots or architectural etc., "flat"
subjects it is a different situation and I prefer more the rendering a Tevidon for instance will
give with high sharpnesss + contrast and flatfield over the whole image. I get a bit burnt out
if I see too many swirly images after another.... Wink


PostPosted: Mon Nov 30, 2009 3:01 pm    Post subject: Reply with quote
Not really an "odd" lens, but the famous slim CZJ Biotar 1.5 7,5cm (75mm) red T on Lumix GH1, shot fully open:













and I also had the Kinic with me, perfect for that subject:





PostPosted: Mon Nov 30, 2009 11:39 pm    Post subject: Reply with quote
kds315* wrote:
Not really an "odd" lens, but the famous slim CZJ Biotar 1.5 7,5cm (75mm) red T on Lumix GH1, shot fully open

Thank you Klaus for these refreshingly straight images. You know how to make the old Biotar sing.

Cheers!

Abbazz


PostPosted: Tue Dec 01, 2009 12:05 am    Post subject: Reply with quote
Thanks Sebastien, well it is the one (my 2nd) I have for sale here on the forum and the proof that it delivers!!


PostPosted: Wed Dec 02, 2009 1:08 pm    Post subject: Reply with quote
Abbazz wrote:

You know resistance is futile Wink ...

Cheers!

Abbazz


I know...
Klaus


PostPosted: Mon Jan 18, 2010 3:34 pm    Post subject: Reply with quote
Here are some of my favorite shots from my 1week old C-mount gear.
GF1, Angenieux 25mm f0.95 (crop to 50mm in M43)

[img]http://farm5.static.flickr.com/4001/4278684253_84b3b168de.jpg
stealth street photography[/img]


my new playmobil photography model


indoor shot of cookie monster ride at shopping mall


colleague at cafe


flora shots near workplace....would love to shot more flora but need to find time[img][/img]
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