[Vicioustuna2012]

So I'm trying to do some macro stuff, and I've gotten some good results, but also have a weird issue. I've been getting some light spots in the center of some pics that almost looks like flare, but not quite. I've posted some pics below (some with, some without the spots). I have no dedicated macro lenses, so I'm using an extension tube, or lens reversal mount. This happens with multiple lenses using the extension tube, and it happens simply reversing the lens as well, so I doubt that the extension tube is the culprit. Is this simply lens flare, and do they make a hood you can mount to a reversed lens?

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Last edited by Vicioustuna2012; 03-16-2017 at 04:18 PM.

[johnhilvert]

It's too subtle for me to see the issue. Most lenses have some vignetting tendencies anyway.

These can usually be fixed in post processing.

[grahame]

It is probably the light reflected from the sensor and bounced back by the last element to sensor. Older lens before digital time? Quite common actually. visible at small aperture.

[vonBaloney]

Center hot spots are often from sensor reflections at smaller apertures. So if you have a reversed lens, light is bouncing off the front element of the lens (which is acting as the rear element, towards the camera) and then back to the sensor, back-and-forth. Or it could be the aperture blades themselves if they are somewhat shiny on the front side (which are faced in reverse). I really only see it in your first photo though. Does it get worse the smaller the aperture?

[Vicioustuna2012]

Center hot spots are often from sensor reflections at smaller apertures. So if you have a reversed lens, light is bouncing off the front element of the lens (which is acting as the rear element, towards the camera) and then back to the sensor, back-and-forth. Or it could be the aperture blades themselves if they are somewhat shiny on the front side (which are faced in reverse). I really only see it in your first photo though. Does it get worse the smaller the aperture?

You know, that's one factor I haven't tested. I'll definitely check for that now. Also, it seems to be most apparent whenever I photograph more reflective surfaces like coins or metal. Could that have something to do with it

---------- Post added 02-12-17 at 10:43 PM ----------

It is probably the light reflected from the sensor and bounced back by the last element to sensor. Older lens before digital time? Quite common actually. visible at small aperture.

Yes, all my current lenses are older:

* SMC-M 50mm f/1.7
* SMC-M 28mm f/3.5
* SMC-M 70-150mm f/4

Yea, I'm using a tight aperture to get a better dof with the macro shots. So, is this unavoidable with my gear? If there's no way to mitigate it during shooting, what's the best way to fix it in post (using lightroom/photoshop)?

[vonBaloney]

Any sort of reversed lens will be somewhat unpredictable -- new or old could cause a problem -- depends on lens shape and coatings. Using a lens normally you have to watch out for older lenses with flat rear elements and there are a few with aperture blades that cause reflections. (And an old lens might have loss of interior paint, etc). Also crappy extension tubes that might not be as light-absorbing along the edges as they could be (or anything scratched in the light path that has become silvery/shiny). Also look for light leaks around the mounts when using any weird set-ups. The angle of the light in the scene can also make a difference. Very often background diffuse light is a bigger problem than direct light (photographing something indoors with a bright window behind it, even if the light source isn't in the shot), but it just depends. Play around with it and different angles and apertures to see when it gets better/worse. In post a localized loss of contrast can usually be compensated for, but sometimes you get a fairly hard aperture-shaped hot spot that is blue or purple with definitive edges -- a bit more challenging...

[Not a Number]

If you have filters on the lenses try taking them off.

[vonBaloney]

Oh one other thing -- you can get light through the viewfinder/eyepiece, so if you are not shooting with your eye to the camera, cover that up. (True any time if you are using remote or timed release.)

[photoptimist]

There's actually TWO common causes of this:

1. reflections from sensor-to-lens and back. This cause will be much stronger for some extension tube or bellows distances and weaker for either longer or short ones. Other than avoiding the worst extension lengths, there's not much to be done because it's intrinsic to the lens design.

2. reflections off any shiny part of the interior of the extension tubes and reversing ring. This will be worst if area OUTSIDE the narrow field-of-view around the subject matter is brightly lit. Matte black paint, strips of adhesive-backed felt, or a lens hood can help.

[TaoMaas]

I'm going to vote for light reflecting off the sensor, too. When you see that a lens was "designed for digital photography", many times that means the rear elements of the lens were coated to help prevent flare from the sensor. It wasn't a problem in film days so most lenses from that era don't have that. It's been my experience that this only shows up under certain conditions and you seem to have found one.

[leekil]

How are you lighting your macro photos? It could also be as simple as flare happening due to light hitting the object unevenly, or entering the lens in the front, like normal sun flare. I have had this problem when I constructed my own flash macro lighting setup with improvised diffusers.

[Vicioustuna2012]

I'm going to vote for light reflecting off the sensor, too. When you see that a lens was "designed for digital photography", many times that means the rear elements of the lens were coated to help prevent flare from the sensor. It wasn't a problem in film days so most lenses from that era don't have that. It's been my experience that this only shows up under certain conditions and you seem to have found one.

A quick update for you, and others in this thread (by the way, is there a way I can update my thread where everyone who posted will get a notification?):

Anyway, I found out the culprit. It wasn't light off the sensor, well, not exactly. It was the macro extension tube I was using. There were some slightly too shiny surfaces inside, and from doing extensive research I found that these surfaces can cause non image forming light to bounce around in the tube and do this...even though there is no light leaks.

To fix it, at first I tried simply taking my macro photos with a black background, and that helped, but not completely. Then I found a nice thread on flickr from some real geniuses ( I would link to it, but I don't know the rules on links to other sites...is that okay?). They suggested I add some baffles made from black card/construction paper to the tube at each end. So, I cut some Doughnut shapes out of the black card with a fairly large hole in the middle (larger than my largest aperture, but smaller than the original opening) to cover any shiny surfaces/I guess keep light from bouncing. I didn't really measure anything, just kinda eyeballed it. I didn't even use glue, but rather just cut the things so that they tension fit into the tube.

So far, it has worked beatifully! No more ghosting. Check it out:

[TaoMaas]

Congratulations! I'm glad you got it figured out.