[kxr4trids]

Okay, cmos flare in this case ... I picked up one of the aforementioned lenses in the original 2.5 variant, but have discovered that it has a purple spot in the center of the frame. Starts to show @ f8 and gets worse as you go up. Underexposed by ~1 to better show. (under by 1 on the meter that is .. obviously since it's metering a white screen...)

Can any of you folks with the 90 duplicate this issue? I would be interested in knowing if this is just a design issue or on a copy by copy basis. Clearly some of it is design, or there wouldn't need to be a Di version..

Would be interested in seeing samples from any version of this lens, the 2.5, 2.8. or Di.

The images attached are f8, f11, f22

There was really only one google hit on this particular lens:

Manual Focus Forum / dSLR and old lenses - sensor filter flaring resistance

interesting link to other lens samples:
ccd_lens_flare_testing Photo Gallery by Pete Ganzel at pbase.com


Edited to add: Thanks for the great replies, look forward to your updates! Added pix of the back of my lens. You can see the nearer surfaces has linear cleaning scratches, while an interior surface has (fungus?) spidery lines. The 2nd pic shows it better. It looks horrible in that light, but it doens't actually show unless you play with the light (which is why I missed the return window on this sucker). The color of the spot definitely looks like the color of the rear lens coating, so whatever the interior stuff is, it's probably unrelated to the flare...

Attached Images

         

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Last edited by kxr4trids; 03-12-2010 at 05:09 PM. Reason: added pix

[pacerr]

Can any of you folks with the 90 duplicate this issue?

Here's a quick cropped sample from a 90mm/2.5 (#53B) at F8 using a K200D. I see no evidence of the spot you mention at any F-stop.

H2

edit: OK, now I've got it unfocused against a blank wall. 1/6th sec @ F22 - ISO 400.

[Mike.P®]

Adaptall 2 72B 90mm f2.8 macro at F8 and F11.

Nothing there.

[Nesster]

I've seen it, though not so well defined as yours, with a 52bb. It has to do with strong light coming directly down the pike and hitting off the sensor, then back from the (flat) rear element. Where I see it is e.g. when I was photographing old cameras against a white oak tag background, and had a flash behind the oak tag to make it bright white.

I believe the lenses that have a curved rear element & maybe specifically coated there will not have this issue. FWIW I believe my Yashinon DX 135/2.8 also suffers from this.

visible here as a blue haze on the bellows

[kxr4trids]

Pacer, I do see it faintly in your image, over the "sis" in "basis". any chance you could post up one @ f22? Also, does your lens have any cleaning marks on the rear element?

Mike, your image looks pretty clean to me too - There's a hint of it over the "90" at f11 but only see it because I'm looking for it. How's your rear element look?

My copy (52B) has some very fine cleaning scratches on the rear element, and the 2nd element (or group) in has some fine spider cracking in the coating. I don't think it's fungus, and you can't see it without careful inspection. Have googled for problem lenses and not seen a similar condition.

The rear surface of the lens appears to be concave.

[Mike.P®]

Rear element is clean.

I have a mint 52B upstairs so I will dig it out tomorrow and see how that fares,

[MattGunn]

...My copy (52B) has some very fine cleaning scratches on the rear element, and the 2nd element (or group) in has some fine spider cracking in the coating. I don't think it's fungus, and you can't see it without careful inspection...

It is very unlikely that the coating on the lens has cracked in any way, it will be less than 0.000001mm thick and therefore relatively flexible and should only crack if the lens is broken. It is most likely to be fungus but providing it is kept dry it shouldn't spread, progress or cause any problems.

I have never observed the problem you mention with my 52BB but have never looked for it. I will try to test over the weekend.

[kxr4trids]

Update: The SP 2x Adaptall teleconverter removes the purple spot. I see maybe a hint of color, but not sure if I'm just making myself see something that isn't there. Image taken at F22(F45tele)

[chrism_scotland]

I've been looking to buy a 90mm Tammy Adaptall for my K20D, but someone elsewhere has put me off a little due to this purple flare, is it a big issue?
I was tempted my the relatively low price of the Adaptall lens and its supposed image quality but I don't really want to throw away money.

[Lowell Goudge]

although I believe it is off the rear element (which , no offence looks like it was cleaned with sand paper) you may also wish to look at some of the bright and shiny parts of the lens mount.

I had a rikenon 135F2.8 that had a horrible reflection because the rear mounting ring for the rear element was shinny not flat black. Someone else had a similar issue with a 645 adaptor that was shinny not flat. The only reason I don't think this is too likely is that in both these cases the reflection was a circular ring , but also gor more defined as you stopped down, just like your case

[excanonfd]

K20D & SP90/2.5 52BB: mounted on a monopod, at f11,16, and 22.

I don't see anything that OP has described.

[duncsuss]

For a while I had a 52B -- on my K10D, I got a rectangular purple patch in the middle of shots, especially in very bright sun.

[macTak]

I noticed the effect too when I had a 52B for a little time. It only started showing up above (or maybe at) f8, and depending on the background of the shot, you couldn't always see it. I wouldn't call it a huge problem, but it is something to keep in mind.

[rhodopsin]

I have both 52B and 52BB. The central hot spot appeared for me when using 52BB (the 2nd version) on Canon XT (crop sensor), the lens is basically unusable on crop sensor imho. I've had 52B (the 1st version) on FF Canon 5Dc for the past few weeks, no hot spot that I have seen. Now I wonder if 52BB has hot spot on 5Dc. When I locate the 52BB () I'll be trying it on the 5Dc, to determine if the problem exists on FF.

As said previously, the hot spot I believe is due to reflections from the sensor bouncing off the nearly flat rear element back onto the central part of the crop sensor, etc..

My previous examination of 52B and 52BB determined the lenses have identical optical components, the 52BB body is a little longer, has rubber focus ring covering, and has larger filter size. But now I'm not so sure, will keep you posted!

[JVi]

I have the 52B version with a skylight filter on it. I get no such glare at f8 (or any other) when pointed at the laptop monitor.