What is going on here? Chromatic Ab? Flare? (Tessar photo attached)

[lueej]

Sorry if this is the wrong forum, but I thought this might be a good spot to ask:



What is the proper term for this? Chromatic Aberration? Flare?

What exactly is happening to cause the rings here and what should I use to prevent them? A lens hood? Shorter exposure time? They are on a few of my negatives, long exposures of around 5-10 seconds at ~f/11 with a Mamiya Super 23 & Mamiya Sekor 100mm f/3.5 lens. Quick and dirty Epson V500 scan with a few LR adjustments.

I've seen people who hold this particular Tessar lens in low regard and say it is only good stopped down/say it is a good lens "for a Tessar." Not sure what they mean.

I'd appreciate any info! thanks RFFers.

 

[willie_901]

I would speculate this is an odd form of flare caused by reflection and then refraction of the bright, point-source light.

What's odd is the symmetrical shape with a tight refraction pattern.

I'm wondering if you had a lens filter attached. In cases like this one must also ask the annoying question about a fingerprint or other oil-based soiling of the glass.

It has nothing to do with longitudinal or lateral CA.

 

[lueej]

I would speculate this is an odd form of flare caused by reflection and then refraction of the bright, point-source light.

What's odd is the symmetrical shape with a tight refraction pattern.

I'm wondering if you had a lens filter attached. In cases like this one must also ask the annoying question about a fingerprint or other oil-based soiling of the glass.

No lens filter attached, and the glass was clean. Only dust inside the decades-old lens as well, and maybe some hard to discern light scratches.
Any suggestions on remedying this effect? I'm guessing a hood?

 

[Ranchu]

No remedy for this, imo, light source is in the frame. Is there bright metal inside the lens, by the elements?

 

[lueej]

No remedy for this, imo, light source is in the frame. Is there bright metal inside the lens, by the elements?

Nothing appears to be inside the lens near the elements, but this is now looking suspect to me. The filter thread is quite reflective and right in front of the front element. Is it possible that it is causing the reflection/refraction?

 

[Dan Daniel]

Intersting idea, that it is the lens mount. I'd be curious ot see if flattening the silver area eliminates this problem. I have a couple of old lenses with that style of mount.

You could use a black step-up ring to cover the silver area. Or simply pull the glass from a cheap UV filter and put it in place. Most screw-in ens hoods will cover the threads.

 

[kbg32]

I believe that is called spherical aberration. It is an intrinsic part of that particular lens design. There is not much you can do, except to avoid photographing in particular situations where you know it might occur, like the one you posted above.

I have an old pre-aspherical 35mm Summilux that exhibits a particular flare that I quite enjoy.

Either you embrace the particular personality of the lens, or find something else.

 

[Corran]

That is not spherical aberration.
http://en.wikipedia.org/wiki/Spherical_aberration

It is clearly an odd flare caused by some sort of reflections somewhere. It just happened to be a rainbow effect (kinda neat IMO).

 

[lueej]

I believe that is called spherical aberration. It is an intrinsic part of that particular lens design. There is not much you can do, except to avoid photographing in particular situations where you know it might occur, like the one you posted above.

Either you embrace the particular personality of the lens, or find something else.

That is not spherical aberration.
http://en.wikipedia.org/wiki/Spherical_aberration

It is clearly an odd flare caused by some sort of reflections somewhere. It just happened to be a rainbow effect (kinda neat IMO).

I'm going to order a step up ring 40.5mm-49mm and test it out at the same spot to see if it is in fact a reflection from the filter thread, or Spherical Aberration.

I'm also considering a hood but will try with just the step up ring first. Would anyone have any idea if this hood (49mm pentax mh-rc) would hinder coverage (100mm on 6x9)? It would look to offer the most protection from stray light. I compose with ground glass on the Super 23 so I suppose I might be able to see for myself if I just splurge, but knowing would be nice.

I appreciate all the replies and hypotheses!

 

[Ranchu]

You know what might be cheaper is a step down ring (or various to test) instead of that cool hood. You could also figure out how big the hole is in it, and cut a piece of paper to test on your ground glass...

 

[Dan Daniel]

Would anyone have any idea if this hood (49mm pentax mh-rc) would hinder coverage (100mm on 6x9)? It would look to offer the most protection from stray light. I compose with ground glass on the Super 23 so I suppose I might be able to see for myself if I just splurge, but knowing would be nice.

That Pentax hood is for the 40mm Limited lens, I believe. That's a lot to pay just to kill some glare. And if the design was truly effective, not just sorta-ok and compact, I think other companies would have started using it.

I would suggest sticking with standard hoods while you trouble shoot this. You could even use matte black tape to cover the silver as a quick test.

 

[lueej]

You know what might be cheaper is a step down ring (or various to test) instead of that cool hood. You could also figure out how big the hole is in it, and cut a piece of paper to test on your ground glass...

Can't believe I didn't think of that! Good idea. However, I just ordered a step up adapter! I figured it wouldn't hurt seeing as I have a spare 49mm rubber hood lying around and nothing to use it on. At $4 shipped with a free micro fiber cloth, it wasn't a big hit to my wallet.

You could even use matte black tape to cover the silver as a quick test.

Great suggestion. I'll give this one a try soon!

 

[kbg32]

Let us know if the hood works. I would love to see a similar image with a similar light source.

 

[Ranchu]

Tape the black ring too, at the light levels you're shooting at it may be reflecting some as it's shiny rather than matte black. Call me paranoid but what the hell..

🙂

 

[lueej]

it looks like it worked...sort of.

with the step up ring + tape blocking the threads:


with the step up ring covering the threads, this still happens (straight flat scan). this can be fixed with the exposure and curves tools to a certain extent.


both were taken at the same aperture (f/11), the top one having a longer exposure by a tiny bit...so I'm still not sure what is going on.
when viewing both on the ground glass wide open, rings of light like the ones exhibited in my first post in the thread are visible, but they are a lot more pronounced when viewing the top photo of this post.

anyhow, here are some more results from the same roll:

 

[Ranchu]

Oh, hey. I missed this. Thanks for reporting back! This is good information!

🙂