Vivitar 28mm F1.9 exposure issue.

Hello all,
I found this lens in great condition, already converted to eos, so I went for it and bought it.

However, I found out that what I early thought was a strong vignetting is too much to be called so:
I have to compensate 2 stops of exposure from f1.9 to f4, where I compensate about 1 stop, and finally have a correct exposure (without compensating) only from f8.

Serial Number 37600837

I made a short video to show you the lens.
Feel free to skip the last part, just playing with the smooooth focus ring.

http://youtu.be/zJfJpj​h66GE

and here are three exposures,

@ f1.9

Nick.S wrote in post #13834955
Hello all,
I found this lens in great condition, already converted to eos, so I went for it and bought it.

However, I found out that what I early thought was a strong vignetting is too much to be called so:
I have to compensate 2 stops of exposure from f1.9 to f4, where I compensate about 1 stop, and finally have a correct exposure (without compensating) only from f8.

Serial Number 37600837

I made a short video to show you the lens.
Feel free to skip the last part, just playing with the smooooth focus ring.

http://youtu.be/zJfJpj​h66GE

and here are three exposures,

@ f1.9

@ f4

@ f8

Note that it does not happen when in Live View, where the camera auto-adjusts the exposure..

It's the only manual-aperture lens I've tested on my 40D to date, so no other info on that, but it should get the exposure through the lens working in stop down metering.. am I missing something?
Everything seems fine from f8..

On the conversion, well It was originally a Minolta mount, I don't know exactly how he converted it, looks like it goes quite beyond infinity focus so on the other end minimal focus distance is more than the original 30cm/12 inches, like 45/17inches, but it's not a great issue for me.

As long as this isn't linked with the exposure problem!

Thanks guys,

Nick

I tried one of these on a 5D. It's a Nikon mount with a chipped adaptor. It works fine - no problems with exposure.

Sorry if that's not a lot of help but it suggests that you problem may have something to do with the conversion and maybe the lens being too close to the film plane?

Although the "spec" distance are not an issue to you it may very well be related to the issue you are having. If the distance from the lens rear element to the defined focal plane was maintained in the conversion then the spec distances would not be off tolerance. The fact that they are, and by significant amounts, indicates little if any care was paid to the lens mounting distance. I would be suspucious that this is also a major factor of the behavior and resulting images presenting issues.

Personally I would return the lens if possible and exchange to something that hasn't had any conversion. I might also be inclined to stay away from "slightly old" Vivitar lenses in general (made in China??). They were pretty poor quality a few years ago although I understand a new and improved line came out in the last year. I loved Vivitar lenses back in th late 19060's - the stuff they turned out under the Series 1 label were very good quality both from the build standpoint and image quality.

Lastly, are you getting any of the vignetting from a "protective filter"? If mounted try removing it and doing a retest.

I see you're working with a 40D.... it's often helpful to identify the camera when looking to debug a problem. It also looks like the lens' aperture blades are working properly. I'm surprised that a crop camera would exhibit such large apparent vignetting in a lens that's intended for 135 format.

Anyway, we can attempt to diagnose things. It's very difficult to look at vignetting when you don't have a uniformly illuminated subject. It may be boring, but try pointing your camera straight up at the ceiling. Illuminate it as uniformly as possible by shining a light downward toward a white reflector (a sheet or white t-shirt will work fine.) A two-bounce solution is even better.

You should then mount the camera on a tripod looking straight up, focus then use the centre point and meter the light with (say) the lens wide open. Set it up to take manual exposures then take a set where you decrease the aperture by one stop and increase the exposure (also by one stop.)

That'll give you a series that's independent of your camera's electronic tom-foolery. Perhaps you could post these images.

If the problem persists, I wonder whether it's related to some of the strangeness that Wilt wrote of a while back (around 18 May but I can't find the thread.)

John from PA wrote in post #14665013
Personally I would return the lens if possible and exchange to something that hasn't had any conversion. I might also be inclined to stay away from "slightly old" Vivitar lenses in general (made in China??). They were pretty poor quality a few years ago although I understand a new and improved line came out in the last year. I loved Vivitar lenses back in th late 19060's - the stuff they turned out under the Series 1 label were very good quality both from the build standpoint and image quality.

This is an old 1970's lens, made by Tokina. From the serial number the poster gave, it looks like it was made in 1976. It was quite expensive in it's day - not far off the price for a Canon 28mm f2.0. I got mine from a camera shop for about £25 . An unconverted one with a Nikon or Olympus mount can easily be used with an adaptor.

Nick.S wrote in post #13834955
However, I found out that what I early thought was a strong vignetting is too much to be called so:
I have to compensate 2 stops of exposure from f1.9 to f4, where I compensate about 1 stop, and finally have a correct exposure (without compensating) only from f8.

Note that it does not happen when in Live View, where the camera auto-adjusts the exposure..

It's the only manual-aperture lens I've tested on my 40D to date, so no other info on that, but it should get the exposure through the lens working in stop down metering.. am I missing something?
Everything seems fine from f8..

It sounds like you are complaining of two phenomenon

1. vignetting
   
2. inaccurate exposure in stop down metering

Thanks guys,
long story short I found by myself some months ago the solutions (or better some workarounds) since i needed to use it for a small work.
The problem, as stated above, is the incompatibility of the eos metering with the stop down metering method.
I chipped the lens to f2.8 aperture (max is f1.9) so when i need i can stop it down or open it up without many exposure problems until f.6.3 or smaller.

Another workaround i recommend if you have to use stop down metering and have no chip is to set the CUSTOM FUNCTIONS as if you had the precison matte focusing screen Ee-s (5d) or ef-s (40d) installed: this way you trick the camera software and somehow you'll get better exposure on the wide open-ish side, experiencing the infamous problems only from -again- smaller apertures like f4/5.6and so on, where i still recommend using the live view function of your camera or compensate the EV if it's possible.

this is a trick that worked for me when i needed it, so i believe that my experience could be useful for other 'vintage glass' lovers that do action photography like me. Not many I guess.