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Need help/tips/recommendations for photographing crystals
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Lou Jost



Joined: 04 Sep 2015
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Location: Ecuador

PostPosted: Fri Jul 28, 2017 8:33 am    Post subject: Reply with quote

Same here, the only IF lenses I know that don't move their exit pupils with changes of focus are on bridge cameras with non-interchageable lenses. These make fantastic tools for wide angle macro stacking photography, duplicating the functionality of the sensor-shifting DIY cameras that Charles Krebs and others made for the purpose. The models I have used are the Lumix FZ200 and FZ300.

I remember your wide-angle matchstick stacks here somewhere....
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ChrisR
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PostPosted: Sun Jul 30, 2017 12:26 am    Post subject: Reply with quote

They're unlikely to be used for best quality studio work though. The "other macro lenses" would be more interesting.
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Lou Jost



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PostPosted: Sun Jul 30, 2017 3:52 pm    Post subject: Reply with quote

You could make such a lens by coupling two lenses front-to-front with a paper stop sandwiched between them, and focusing the rear lens. Might work for very shallow stacks.
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mjkzz



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PostPosted: Mon Jul 31, 2017 3:20 am    Post subject: Reply with quote

it seems you have some hot spots, my 2 cents, you can try some experiments I did here and see if it happens to you.
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Lou Jost



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PostPosted: Mon Jul 31, 2017 5:04 am    Post subject: Reply with quote

That's a very nice video you've made; makes the point very clearly.
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Daniel_Han



Joined: 29 Dec 2015
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PostPosted: Tue Aug 01, 2017 6:00 am    Post subject: Reply with quote

My 85mm f/2.8 Micro-Nikkor PC-E does have an effective aperture at different focus distances, I think I pointed it out somewhere above -- I could be wrong.

This means the iris mechanism effectively moves with focusing I guess, which could lead to some issues. Perhaps I'll try with PN, configure it for 1:2.
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Daniel_Han



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PostPosted: Tue Aug 01, 2017 6:03 am    Post subject: Reply with quote

Awesome video Peter! Yep, I think diffusion is important in my case as well. My post pretty much illustrates a lot of rookie mistakes Razz It's a combination of different problems!

I have some more crystals coming in this month, worth to try some of the mentioned diffusion methods. This Herk is too big for a cup/pingpong ball diffuser.
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rjlittlefield
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PostPosted: Tue Aug 01, 2017 8:49 am    Post subject: Reply with quote

Daniel, have you had a chance to do that test I suggested HERE (previous page of this topic), checking for apparent motion of features inside the crystal?

--Rik
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Lou Jost



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PostPosted: Tue Aug 01, 2017 10:08 am    Post subject: Reply with quote

That's a problem I wish we all had more often--a diamond too big for our diffusers!
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Daniel_Han



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PostPosted: Wed Aug 02, 2017 9:39 am    Post subject: Reply with quote

rjlittlefield wrote:
Daniel, have you had a chance to do that test I suggested HERE (previous page of this topic), checking for apparent motion of features inside the crystal?

--Rik


Yep, surely! It will probably have to be next week though. I was silly enough to run through the rain and not shower afterwards, now I have a cold! Boohoo poor me, silly me Rolling Eyes

I'll post my findings here Very Happy
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Daniel_Han



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PostPosted: Sun Aug 06, 2017 5:32 am    Post subject: Reply with quote

rjlittlefield wrote:
Daniel, have you had a chance to do that test I suggested HERE (previous page of this topic), checking for apparent motion of features inside the crystal?

--Rik


Hey Rik! I followed the steps you provided and the checked the "Show as Adjusted" box, scrolled through the entire stack with arrow keys and I was not able to observe any movement.

I had the image zoomed in 100% and located some big air bubbles near the "rainbow". Scrolling through, I can see no movement at all.

However as I scroll through, obviously, the bubbles go from "defocus blops" to sharp, to "defocus blops", and a clear "dual line" rendering can be seen.

This is what I'm talking about:
Curious Bird by Daniel Han, on Flickr

See how the branches in both the foreground and background exhibit some sort of "business"? Some are rendered as 2 lines, and this is what I'm kind of seeing.

Maybe this is the culprit, it's going to be tricky to fix actually. Maybe exporting all the adjusted jpegs, loading into photoshop and doing lots of cleaning could work.

I have a rutilated smokey quartz crystal, might give that fellow a go to see how Zerene Stacker handles all the lines.
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rjlittlefield
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PostPosted: Sun Aug 06, 2017 6:16 pm    Post subject: Reply with quote

Daniel_Han wrote:
I followed the steps you provided and the checked the "Show as Adjusted" box, scrolled through the entire stack with arrow keys and I was not able to observe any movement.

OK, good. Then let's go back to the beginning.

Here is a 2X enlargement of part of "Attempt 3" in your initial post:


You described the effect as "smudged and blurry", but that's not what I see.

What I see are two sharp copies of every feature, with a slight offset between the copies.

In terms of the source images, the only way this can occur is if each feature occurs at two different pixel coordinates, after alignment, either:
(A) in the same frame (where it should be immediately obvious) or
(B) in two different frames that are separated far enough in depth that you don't make the correlation.

With this further explanation, I suggest going back and taking another look at this part of the stack. I will be very interested to hear which case you have.

After that, we're looking for a physical cause for why each feature appears at two different places.

If each feature appeared multiple times in a line, brightest and sharpest in the middle of the set and progressively less bright and more blurred toward either end, then I would again think apparent motion.

But at least in this area we only see two copies, equally sharp.

That fact, plus your report of no observed motion, makes me think that either:
(A) the lens happens to be looking simultaneously through two surface facets that are slightly displaced from each other, or
(B) you have the stone oriented at an angle where it is exhibiting detectable birefringence. According to http://www.quartzpage.de/gen_phys.html, quartz has only about 1/20 as much birefringence as calcite, but when you're zoomed in to this level of detail, I'm thinking that would be enough to cause the effect we see here.

Quote:
However as I scroll through, obviously, the bubbles go from "defocus blops" to sharp, to "defocus blops", and a clear "dual line" rendering can be seen.

This is what I'm talking about:
(image)Curious Bird by Daniel Han, on Flickr

See how the branches in both the foreground and background exhibit some sort of "business"? Some are rendered as 2 lines, and this is what I'm kind of seeing.

I think the operative phrase is "kind of".

What I see in the bird image looks like one of the usual ways in which bokeh can go weird, due to interactions between the subject orientation, the orientation of vanes in your lens iris, and sometimes spherical aberration in the lens. I have one lens that's just awful in that regard -- many features of the scene that are physically sharp but out-of-focus turn into hard-edged blobs that make the background look "busy" even though it's all out of focus.

But this bokeh effect will not cause the clear doubling of focused features like we see in the Herkimer diamond crop.

--Rik
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Daniel_Han



Joined: 29 Dec 2015
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PostPosted: Mon Aug 07, 2017 7:12 am    Post subject: Reply with quote

Thanks for your insight and help Rik! I'll try explore this problem further and see what's the problem.

I decided to look into my Dmap stack, and found some interesting problems.



In certain areas, we can see a duplicate of equally sharp inclusions, but in certain areas, we can't.

For the Pmax stack, the details are just rendered as smudges and blops. I'll check out the link you provided as well.

Edit: That article seems to go into extreme detail, I'll have a look tomorrow night if I have time.
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