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Troubleshooting
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kaiotaku



Joined: 27 May 2012
Posts: 22
Location: Melbourne, Australia

PostPosted: Sat Oct 07, 2017 7:26 pm    Post subject: Troubleshooting Reply with quote

Hi all,

So recently I did a test stack using the Sigma 150mm macro with Mitutoyo 20x. I was very displeased with the results and assumed that the Sigma must be a bad tube lens.

However, I'm working on a major project this week and upon returning to using known good combinations of lenses and objectives it seems like ALL my images are bad. And I mean really bad.

I'm using flash, so it can't be a vibration issue I think. Nothing had been dropped or damaged in any other way, but in any case it just seems like all the images are garbage, regardless of what I do.

I'm utterly exasperated by this, and started to feel quite depressed about it. Has anyone else experienced anything similar?
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Chris S.
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Joined: 05 Apr 2009
Posts: 2850
Location: Ohio, USA

PostPosted: Sat Oct 07, 2017 8:22 pm    Post subject: Reply with quote

Kaiotaku, sorry for your troubles!

Could you post a few examples, some technical details, and perhaps a quick snap of your setup, including the lights?

--Chris S.
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ChrisR
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Joined: 14 Mar 2009
Posts: 7261
Location: Near London, UK

PostPosted: Sun Oct 08, 2017 2:11 am    Post subject: Reply with quote

Quote:
it just seems like all the images are garbage, regardless of what I do.
...
Has anyone else experienced anything similar?

Only when there's an "r" in the month, or May-August.

Focus the 150mm at infinity.
Make sure the lenses connecting adapter isn't causing light to bounce around (a flat, black one is fairly safe).

Start with a physically flat, and non-reflective subject, like a postage stamp or banknote. Hold it flat relative to the sensor

Put a lighting diffuser near the subject. White paper is fine. You need ridiculously diffused light.

Expect a tenth of not much, to be in focus. (about 10 microns , = 0.01mm) Shocked

See what happens then!.
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kaiotaku



Joined: 27 May 2012
Posts: 22
Location: Melbourne, Australia

PostPosted: Sun Oct 08, 2017 8:10 pm    Post subject: Reply with quote

Thanks for the initial thoughts. So here is one of the setups I tested.

This is a Stackshot rail, Canon 70D with a Mitutoyo 20x mounted on a Canon 200mm f/2.8.

So a fairly basic setup. I also have a Nikon 10x which I use either on the 200mm or on a 100mm f/2.8 macro non-L. I did a test image with exactly this rig a few months ago, in anticipation of the current project, and was very very pleased with the results. However, something is wrong now.

None of the images getting captures show any evidence of being sharp. So it isn't any kind of software issue. The light is an Elinchrom. If all my equipment - all of it - had been dropped on the ground, I could understand, but currently I just don't understand.

I woke up yesterday to take nice images, not to troubleshoot my gear. So I quickly got angry and decided to play Gears of War 3 instead. I'll have to come back to it when I have a clear mind. But I just can't understand it, nothing should have changed from previously.

I really hope there is nothing wrong with the Mitutoyo, it's such an expensive component.
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kaiotaku



Joined: 27 May 2012
Posts: 22
Location: Melbourne, Australia

PostPosted: Sun Oct 08, 2017 8:10 pm    Post subject: Reply with quote

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kaiotaku



Joined: 27 May 2012
Posts: 22
Location: Melbourne, Australia

PostPosted: Sun Oct 08, 2017 8:13 pm    Post subject: Reply with quote

By the way, the light is quite diffuse, and I checked the basic things like the lenses being set to infinity, aperture set correctly, etc.
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Chris S.
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PostPosted: Sun Oct 08, 2017 8:57 pm    Post subject: Reply with quote

kaiotaku wrote:
By the way, the light is quite diffuse. . . .

I don't see any significant diffusion shown in the setup picture you shared--just a bare flash in reflector, and what looks like a small flag whose purpose isn't obvious. Can you explain?

If you show us some images that you don't like, along with the setup that created them, it might be a big help.

--Chris S.
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kaiotaku



Joined: 27 May 2012
Posts: 22
Location: Melbourne, Australia

PostPosted: Sun Oct 08, 2017 9:13 pm    Post subject: Reply with quote

Thanks Chris. Between the grid and the subject there are 2 little squares of diffusing material, I think what might be called thin `wadding' (?), about 3 mm thick, cottony sort of stuff. Same as I've used in the past, found it quite useful as a diffuser. For shells I usually prefer a moderately directional light rather than a fully diffuse one which might be employed commonly for insects.

Here is a downsized full image and a 100% crop. Just horrendous, as you can see. The seems to be something very wrong optically.

This is just a quick partial stack to see what I was getting, because I knew that the full stack wouldn't be worth it.



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Chris S.
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PostPosted: Sun Oct 08, 2017 9:37 pm    Post subject: Reply with quote

kaiotaku wrote:
Between the grid and the subject there are 2 little squares of diffusing material. . . . Same as I've used in the past, found it quite useful as a diffuser. For shells I usually prefer a moderately directional light rather than a fully diffuse one which might be employed commonly for insects

Let me suggest you try full diffusion--not for aesthetic reasons, but for a technical one--and see if your problem goes away. It very well might. (Or conversely, try shooting a very non-shiny shell with your existing lighting, and see if it looks better.)

Like you, I prefer somewhat directional light in many cases (and don't do insects). However, with shiny subjects, directional light can destroy resolution by using, effectively, only a small portion of your lens' entrance cone. For shiny subjects, I often find it easier to start with very diffuse light, then subtract light a bit at a time to get more illustrative modeling, while balancing this against loss of resolution.

This subject appears to be very shiny. Were your prior shells this glassy? If not, you may well have achieved excellent resolution with a narrow light source.

As a matter of perspective, the two little squares of diffusing material occupy only a small portion of the "sky" as seen by your subject; even with a matte subject, this is probably very directional lighting by most photomacrographer's standards.

--Chris S.
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kaiotaku



Joined: 27 May 2012
Posts: 22
Location: Melbourne, Australia

PostPosted: Sun Oct 08, 2017 9:52 pm    Post subject: Reply with quote

Thanks for the input Chris.

I initially had the diffusion panels lower and closer (hence, effectively larger), however in this case (often happens with tiny shells) too much light hitting the shell laterally caused it to penetrate inside and create a "glow from within" effect which is rather unpleasant, results in a too-contrasty look (overexposed / underexposed areas) and is counterproductive in terms of trying to visualise surface detail.

I forgot to mention that there was a scrap of paper on the other side of the shell providing fill, so the overall light is directional but ought to be not too harsh overall.

But, I will try what you suggest, since I certainly wouldn't have suspected the possible problem that you've mentioned.

I'll post my earlier test images with the same combo.
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kaiotaku



Joined: 27 May 2012
Posts: 22
Location: Melbourne, Australia

PostPosted: Sun Oct 08, 2017 9:58 pm    Post subject: Reply with quote

Here are the earlier test images.

Obviously the shell doesn't fit the frame properly, but I chose it deliberately in order to test the corner performance. I already had images of the same shell by SEM and with the 10x Nikon.

This is the overall image, reduced size, and 100% crop. I've really got no complaints here at all. Areas which were mushy using the 10x Nikon are suddenly crystal clear. I just bought a rather expensive stereomicroscope for sorting purposes, and I can't (or can barely) see those interstitial spiral threads using that. To get such a clear image really pleased me. Stack of about 180 at 2 microns.



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kaiotaku



Joined: 27 May 2012
Posts: 22
Location: Melbourne, Australia

PostPosted: Mon Oct 09, 2017 10:52 pm    Post subject: Reply with quote

I think I found in the archives some discussion of the issue which Chris S. was referring to:
http://www.photomacrography.net/forum/viewtopic.php?t=19582&postdays=0&postorder=asc&start=15

I tried the same subject just now with heavy diffusion, alas the results are still filth.

Something tells me that this will be a time-consuming and perhaps expensive fix. Swapping bodies, swapping tube lenses / vs bellows, swapping out objectives, until I see results that I'm happy with.
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kaiotaku



Joined: 27 May 2012
Posts: 22
Location: Melbourne, Australia

PostPosted: Tue Oct 10, 2017 12:39 am    Post subject: Reply with quote

Well, I most certainly was not imagining things.

I went back and imaged the same sample as before, using the same equipment:



Versus previous:



That's the same camera body, tube lens and objective. Virtually same technique.

However, if I use my 10x Nikon objective things also look bad. So `hopefully' this is a problem with the tube lens(es) or, less likely, the camera body. Rather than the precious Mitutoyo.

I also shot the Nikon 10x at 5x on a 100mm and wasn't so impressed with that either, although it could be that my expectations have changed.

I find this utterly bewildering, considering that none of the equipment, to my knowledge, has been slammed on the ground. I'm not going to quit, but it's a massive kick in the guts, for sure.
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ChrisR
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PostPosted: Tue Oct 10, 2017 2:08 am    Post subject: Reply with quote

As nothing is likely, have you really eliminated vibration, or ambient light, as culprits?
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Chris R
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kaiotaku



Joined: 27 May 2012
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Location: Melbourne, Australia

PostPosted: Tue Oct 10, 2017 2:34 am    Post subject: Reply with quote

Hi ChrisR,

I'm shooting 1/200, ISO 100, same as usual.

I tried flicking the focus limiter on the lens but it does not good.

I have wooden floorboards and a not so stable wooden table that I'm shooting on, but I piled up some heavy books on the perspex base to make it more stable. I don't walk around anywhere in the room whilst the stacks run and I see minimal motion if I stand still with the camera in LV. With quick flash I can't see vibration being to blame here somehow.

It's almost like the lens is stopped down causing major diffraction, but it can't be, I'd see vignetting if that were the case. The camera reports f/2.8.

I evicted some sharemates a while back because they were using huge amounts of electricity, gas, water and internet and refusing to pay a fair share of the bills. I wonder if they didn't exact revenge by dropping all my lenses on the floor. I was away on a business trip when they moved out. But perhaps I'm clutching at straws.

Not sure where to go from here except trying to rent another 200mm f/2.8 or use a bellows, and see what happens, maybe use another microscope objective (was thinking of getting a Mitutoyo 10x).
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