Frustrating center blur/overexposure problem.

Arvee · Apr 17, 2020

Are you using a single focus point or multi-point focus? Use single point focus and make an exposure at 1.4 and also 4.0. Compare images. Should have good central focus for both apertures except for the softer image at 1.4.

Perform the same test with autofocus off and manually focus on the subject. Report back.

btaylor · Apr 17, 2020

Yikes- so much testing... and then what, find someone to repair it? I think, as the OP suggested earlier, that it’s time to find another example and move on. I would, anyway- life is short.

shutterfinger · Apr 17, 2020

btaylor said:
Yikes- so much testing... and then what, find someone to repair it? I think, as the OP suggested earlier, that it’s time to find another example and move on. I would, anyway- life is short.

It requires more time to post the test here then get a response from the testing person than it does to do it if you have the lens in hand and know how to test it, but once you've been through the procedures a time or two it will go a lot faster.

Sirius Glass · Apr 17, 2020

Frisius said:
@grain elevator and @cowanw
Yes time to get scientific. But, it also takes a lot of time and I'm close to giving it up and just buying a new lens. I'll try to do a test tomorrow, when the sun shines.

I feel the blur occurs mainly (but again- not always) when there's high contrast in the picture. I haven't been able to reproduce a center blur in taking 50 pictures of a tiled floor. The blue shine is there and sometimes creates the sense of a blur, mainly when there's an overexposed rim.
I did find another analogue picture where the center blur is well, I would say, irrefutable.
Sorry for all these bad pictures btw! I'm usually quite artistic
View attachment 244143

The photo looks like a long exposure because both the woman and the man are moving, the woman more so. As suggested in an earlier post you need to do some systematic tests on the lens. At least the camera is not the problem. The lens may need to go for a Clean Lubrication and Adjust [CLA] and adjusted on an optical bench.

cowanw · Apr 17, 2020

Aberrations at wide open can be an issue. Lenses are made to be looked through at wide open and used a stop down.
The light post and curb between the people doesn't look so bad, blue fringing excepted.
You have been frustrated for a long time and you have asked for advise, but if you really just want a new lens go for it.
Or do your tests on the digital camera (and with a tripod) to understand what is happening sooner than never.

Frisius · Apr 17, 2020

@Sirius Glass , No the subjects were standing still and it was a fast exposure.
@cowanw Obviously, I don't want to spend money unnecessarily. But I've been following a lot of tips now and also before I put the question to the forum, I talked to multiple people. I hoped someone here would go "Yes! I know that problem!".
But don't get me wrong, I'm really grateful for all your help and I'm not giving up yet!

But as @Arvee says: if I find the problem, I doubt if I can have it repaired for less than $160, which is what a new second hand would cost. So I'm mainly doing it because I want to know grrr what it is!

Tomorrow more tests, now sleep.

koraks · Apr 18, 2020

Looks like some seriously misaligned lens elements. If it were my lens I'd open it up and see if the problem is visible and correctable. If not, shell out the cash for a replacement.

Sirius Glass · Apr 18, 2020

koraks said:
Looks like some seriously misaligned lens elements. If it were my lens I'd open it up and see if the problem is visible and correctable. If not, shell out the cash for a replacement.

Sell it on eBay as "a superb example of a lenses with rare and greatly sought optical properties".

Wallendo · Apr 18, 2020

The digital image you posted demonstrates a great deal of purple-fringing. If this is a zoomed-in image that might be expected, but if this is the whole image, this is much more than I have ever seen.

Further experimentation could pin down the conditions that lead to this defect, an interesting intellectual pursuit, but I doubt further testing will determine a problem that is user correctable.

I have had this happen once, but have been unable to replicate the problem with the lens and camera for the last 3 years, so I am unable to offer any useful advice, but have followed this thread with interest.

My gut feeling is that if a lens can't be trusted, it should be repaired or replaced.

reddesert · Apr 21, 2020

IMO:
- You probably won't or can't trust this lens and so it would be good to get another one. They are fairly common.
- However, it would be good to do some systematic tests, if only to rule out some camera vs lens issue. The photographs that you've posted are of subjects that are too complex to really tell what is going on. If you want to do a systematic test, I suggest finding a subject like a fence or wall running at an oblique angle, so the left side is near and the right side is far (or vice versa). Take photos focused on the center. Take both an AF photo, and a manually focused photo (turn off AF and focus by eye on the focusing screen, not with the focus indicator). You can also take photos that are deliberately focused ahead/behind of the true focus point, just make sure you write down the order in which you are doing them.
- You can try both wide open and a couple stops down.

Looking at these photos with the fence at a range of distances will help you determine whether the lens + camera are consistently defocused in the middle, or have focus errors ahead/behind the intended subject, and whether there is flare or color fringing localized to a particular part of the frame, etc.

Frisius · Apr 22, 2020

So, okay, I bought a new (second hand) lens (€150) on a classifieds website. Problem solved.
But I still want to find out what's wrong with the old lens but I can't do it digitally because that's not how I work and it wouldn't rule out a problem with the body.
But in order to do that, I'll have to wait until the corona rules become milder and the labs open again.
Until then:
Thanks everybody for your insights and tips!

koraks · Apr 22, 2020

As the crisis lasts, you could try develop your own film - it's not that complicated!

Frisius · Apr 22, 2020

koraks said:
As the crisis lasts, you could try develop your own film - it's not that complicated!

I know, but I'm currently not in the same place as my darkroom. Also, since the problem occurs primarily in color, it does get slighty complicated.

reddesert · Apr 22, 2020

If you try it with the digital camera and you can characterize the lens blur, then you'll have some idea of what's going on; plus you can take more images of test subjects like fences, without burning film. You won't be doing a full system test with the film camera, but that's ok.

Sirius Glass · Apr 22, 2020

The problem lens could make a nice paperweight for your desk.

shutterfinger · Apr 22, 2020

Frisius said:
I know, but I'm currently not in the same place as my darkroom. Also, since the problem occurs primarily in color, it does get slighty complicated.

The only difference between processing color film vs B&W film other than the chemicals used is keeping the chemical temperatures in tolerance. Color requires higher temperature tighter tolerance. Color chemistry does not last as long as B&W chemistry so have several rolls ready to process before mixing the chemicals from powder or concentrate.

The focus issue should show up on either recording medium, fringing may only be apparent on the electronic medium.

Frisius · Apr 23, 2020

@shutterfinger Yes yes but as I said before, it's hard to see the issues on a negative and my scanner is also in the place where my darkroom is, which is about 1200 km from where I am stranded during this virus.
Also, like I've said, the color aberration is visible on the analogue medium.

There are too many variables, (scanner, body electronics, lens electronics, loose elements, back plate, bad film, etc.) so I bought a new second hand lens and I'm very happy with it.
Thanks!

jtk · Apr 25, 2020

Condensation.

removed account4 · Apr 25, 2020

Patrick Robert James said:
It looks to me like there is an issue with an element, or maybe a group. Perhaps someone took it apart and didn't put it back correctly. That is definitely your lens though. No chance something like that could happen in the camera.

^^^^
post #9

Frustrating center blur/overexposure problem.

Arvee

btaylor

shutterfinger

Sirius Glass

cowanw

Frisius

koraks

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Sirius Glass

Wallendo

reddesert

Frisius

koraks

Moderator

Frisius

reddesert

Sirius Glass

shutterfinger

Frisius

jtk

removed account4

Frustrating center blur/overexposure problem.

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