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Esphotos
Tinkerer
Username: Esphotos
Post Number: 8
Registered: 11-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, March 19, 2009 - 08:24 pm: | 
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Hello all,
I have a Contax 139Q which produces low contrast flat images compared to other cameras like Nikon F3 or Canon EOS 30 that I also have. I use Carl Zeiss Distagons and Planars on the Contax. I use these lenses on my Canon 5D with great results so I can safely rule out the lenses for causing the grief.
I have tried a number of different films from cheapy to professionals, colours and B&W, low to high speeds, but all with same results – flat and low contrast. I have taken shots at high/low shutter speeds. Basically I have tried everything I could think of.
I now believe it’s the camera that causes the low contrast. The camera has new light seal installed (by me). The backing plate is springy and pushes the film flat.
Any opinion why the images are so poor?
Here are some examples:
http://i132.photobucket.com/albums/q32/eSRods/Contax537.jpg
http://i132.photobucket.com/albums/q32/eSRods/Contax533.jpg
Cheers
Edward |
Gez
Tinkerer
Username: Gez
Post Number: 56
Registered: 09-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, March 20, 2009 - 01:05 pm: |
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Have you compared the negs to see if they are of normal density? Could just be a large exposure error. |
Mndean
Tinkerer
Username: Mndean
Post Number: 135
Registered: 08-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, March 20, 2009 - 01:31 pm: |
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I'd agree looking at the negatives is the only way to check and see if they are over/underexposed. I don't know that I'd trust a digital camera to test lenses since one could adjust contrast, but since it's more than one lens I doubt they could be the problem. I'm sorry you didn't include a color image to show how they're affected. |
Esphotos
Tinkerer
Username: Esphotos
Post Number: 9
Registered: 11-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, March 20, 2009 - 05:39 pm: |
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Thank you for replies.
I never thought about checking the accuracy (or inaccuracy) of the exposure, I knew I will get some good advices here. I will check that thoroughly, next few days.
Initially, I compared with Nikon F3 and Canon 5D and the Contax gives reasonably accurate meter readings. I know that does not mean the camera shutter will fire accordingly. I will do side by side test with F3 and compare the negs.
I am also thinking that the camera may still have light leak somewhere. Possible?
Mndean, I have included colour photos. Not much better.
Cheers
Edward
http://i132.photobucket.com/albums/q32/eSRods/Contax121.jpg
http://i132.photobucket.com/albums/q32/eSRods/Contax128.jpg |
Mndean
Tinkerer
Username: Mndean
Post Number: 136
Registered: 08-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, March 20, 2009 - 07:49 pm: |
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Both the color shots look to be under very flat lighting conditions - very weak shadows. Not easy to get bold contrast in that light, so I'm not too surprised those look low in contrast. The color seems not too saturated. Best thing to do is take the Nikon and Contax out together with the same film, equivalent lenses if possible, shoot the same scenes at the same time, process the rolls together and see what, ahem, develops. If you've done this already, forgive my ignorance. |
Glenn
Tinkerer
Username: Glenn
Post Number: 533
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, March 21, 2009 - 06:58 pm: |
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It has not been stated if the exposure problem with the Contax is a recent development, or has always been present. Carl Zeiss lenses certainly do not produce 'flat' images, and the presented samples do not offer any evidence of 'light leakage'.
The most common cause of 'flat' images being produced by well computed optics, is poor internal light baffling in the mirror box/interior of the camera. I do not believe the whole 139 production will have been produced with a poorly finished interior (unlike most Russian MF bodies), but you do find rogue examples from some manufacturers that escaped final quality control. A poorly carried out repair or service could also have caused problems - I once came across a a Canon F1 that had some sort of mirror repair/replacement. The underside of the mirror assembly had a nice thick coat of a very glossy black paint on it. In other cameras, over indulgent lubrication had rendered a nice matt finish all nice and shiny. Not the ideal situation for producing contrasty images!
Final note - A digital camera is a good way of checking image quality of various lenses, but only if you use a known good performing lens to set up the exposure data. All the other lenses tested must have their test image exposed to the same parameters. This is obvious if one wants to to a proper comparison, but it often forgotten and just leads to going round in circles and proving nothing! |
Mndean
Tinkerer
Username: Mndean
Post Number: 137
Registered: 08-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, March 21, 2009 - 07:34 pm: |
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Digitals allow enough parameter manipulation that I don't trust that some parameters (contrast, exposure) haven't been adjusted which then may render comparisons misleading, too. I always go same day side-by-side shots with film processed in the same tank (or same lab for color). |
Esphotos
Tinkerer
Username: Esphotos
Post Number: 10
Registered: 11-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, March 22, 2009 - 07:30 am: |
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Thanks all for the informative replies.
I've got that camera about 3 months ago and it was like that from the day I've got it.
Today, I had a thorough check on metering against F3, 5D, and Weston Masters II light meter. All cameras set at 100ISO and fitted with 50mm lenses. At f2.8, the Contax indicated 1/250, F3 1/125, 5D 1/200 and WM 1/150.
At f5.6, Contax 1/60, F3 1/30, 5D 1/40, and WM inconclusive.
Knowing that the F3 exposes correctly, the Contax underexposes by a stop. Would this be the reason?
Unfortunately F3 is loaded with a slide film so I could not test it side by side this weekend.
I am thinking of loading same films and shoot in paellel and process in same tank. I found Nikkor and Planer have very similar quality so lens factor should cancels out.
Glenn, if the internal light box is the problem, is it easy to fix?
Cheers
Edward |
Glenn
Tinkerer
Username: Glenn
Post Number: 534
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, March 23, 2009 - 06:24 pm: |
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Edward,
I think your problem is exposure based and not due to internal light scattering. You can easily check this - Load with B &W neg and find a nice contrasty scene (I run this test indoors), expose a couple of frames as per meter reading and then repeat at 1, 2, 3 and 4 stops over initial reading. Sometimes it is worth doing a couple of exposures at 1 and 2 stops under also, just to prove the point. This will give you an immediate indication of which negs will give the correct print. Basically you are just using 'exposure bracketing' to indicate the metering error.
If the interior of the body is nicely finished in matt/soft black and there a no great shiny areas, then the interior will be OK.
Mark,
One does not alter the parameters during the test. Use a known good lens to produce the reference image, then 'lock' the parameters and produce the test images with the questioned lens/lenses. Obviously you must be able to mount all the lenses on the digital body, but I have used this method a number of times with very good results. |
Mndean
Tinkerer
Username: Mndean
Post Number: 138
Registered: 08-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, March 23, 2009 - 08:42 pm: |
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Glenn,
Ah, but you know that. I do as well, but not everyone will necessarily do it right, which is why I hate to give it as advice. I've seen someone mess up a lens test with a digital. |
Esphotos
Tinkerer
Username: Esphotos
Post Number: 11
Registered: 11-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, March 26, 2009 - 02:53 am: |
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Thanks Glenn.
That's a good idea to test the exposure. I will do that this weekend.
Cheers
Edward |
