Testing a new (flawed) diffuser

Images of undisturbed subjects in their natural environment. All subject types.

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gardenersassistant
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Testing a new (flawed) diffuser

Post by gardenersassistant »

These are rescue shots from a session yesterday where I was testing a new diffuser setup which proved to have a serious flaw which ruined many of the images. I'm hoping an adjustment I made last night will cure the flaw because apart from the flaw the setup seemed to work quite well.

These were captured using a Sony A7sii with two Kenko 2X teleconverters and a Laowa 100mm 2X macro lens, and a Yongnuo twin flash. The raw files were processed with presets in PhotoLab and Lightroom, with image-specific adjustments in Lightroom and output sharpening and noise reduction using a preset in DeNoise AI and a second use of DeNoise AI using a different method, with image-specific masking for some of the images.

There are 1300 pixel high versions of these images in this album at Flickr

#1
Image1934 01 2021_07_06 DSC06227_PLab4 LR 1300h DNAI DNAIc by gardenersassistant, on Flickr

#2
Image1934 03 2021_07_06 DSC06288_PLab4 LR 1300h DNAI DNAIc by gardenersassistant, on Flickr

#3
Image1934 04 2021_07_06 DSC06295_PLab4 LR 1300h DNAI DNAIc by gardenersassistant, on Flickr

#4
Image1934 12 2021_07_06 DSC06361_PLab4 LR 1300h DNAI DNAIc by gardenersassistant, on Flickr

#5
Image1934 13 2021_07_06 DSC06434_PLab4 LR 1300h DNAI DNAIc by gardenersassistant, on Flickr

#6
Image1934 16 2021_07_06 DSC06493_PLab4 LR 1300h DNAI DNAIc by gardenersassistant, on Flickr
Nick

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MarkSturtevant
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Re: Testing a new (flawed) diffuser

Post by MarkSturtevant »

I am hard pressed to see a flaw. The highlight on the femurs of the metallic beetle is perhaps stronger than what you might want. Maybe the light isn't so even in that it seems stronger on the left and right and less so in the center on the springtail.
Mark Sturtevant
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gardenersassistant
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Re: Testing a new (flawed) diffuser

Post by gardenersassistant »

MarkSturtevant wrote:
Wed Jul 07, 2021 4:25 pm
I am hard pressed to see a flaw.
Thanks for the feedback Mark. Substantive image-specific observations are always useful (and are fairly rare).

The problem I was encountering was veiling glare. Here is an example.

Image
1935 1 Veiling glare with version 1 silk layer added to reflector bowl by gardenersassistant, on Flickr

It was variable - I had added a silk layer to the outside of the reflector bowl. It was a bit floppy and some of the time it directed light into the lens. I subsequently tightened up the silk layer (can't get it completely flat) and added an extension to the anti-glare hood on the lens.

Image
1936 1 Anti-glare extension added to refelector bowl with silk layer by gardenersassistant, on Flickr

MarkSturtevant wrote:
Wed Jul 07, 2021 4:25 pm
The highlight on the femurs of the metallic beetle is perhaps stronger than what you might want.
Indeed so. I would love to get rid of that sort of highlight completely, but I think reflections of the flash are inevitable on highly reflective surfaces. The issue then become how strong the highlights are, what they do to colours and how easy/difficult they are to modify locally if one is in to that sort of thing (which I am, but didn't do in this case). In those respects the new setup seems to be doing a bit better so far compared to previous setups, although it is very difficult to be sure because differences in the angle between the subject and the sensor plane can make a big difference to reflections' characteristics. I have other examples with this latest setup where the highlights on those particular beetles are still going yellow at some angles, which I don't like at all. It is complicated though, and not simply a matter of one or more of the channels clipping because that yellowing can occur even when Raw Digger says that no channel is clipping.

It is very frustrating and bothersome.
MarkSturtevant wrote:
Wed Jul 07, 2021 4:25 pm
Maybe the light isn't so even in that it seems stronger on the left and right and less so in the center on the springtail.
Possibly, but I think that sort of thing is too difficult to read from single images. There are a number of potentially conflating factors. One is that I'm photographing in amongst undergrowth and the flash light may be partially obscured by foliage. Another is that the orientations of leaf elements can change a lot across a leaf, for example bending or, as may be the case with that leaf, on either side of a ? radial spine. And the whole leaf may be at an angle to the plane of the sensor. A ball bearing test suggests to me that a hot spot at the bottom of the bowl is probably the first thing I need to take a look at.

Image
1937 7 Ball bearing highlight test by gardenersassistant, on Flickr
Nick

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Re: Testing a new (flawed) diffuser

Post by rjlittlefield »

gardenersassistant wrote:
Thu Jul 08, 2021 3:03 am
I have other examples with this latest setup where the highlights on those particular beetles are still going yellow at some angles, which I don't like at all. It is complicated though, and not simply a matter of one or more of the channels clipping because that yellowing can occur even when Raw Digger says that no channel is clipping.
This suggests to me that the yellow is caused mainly by the subject. Maybe thin-film interference that suppresses blue reflection at some angles? Metallic appearance of insect cuticles is due to many layers of thin films anyway, so there is lots of room for unexpected effects.

Nice work with the ball-bearing test. I think it is an under-appreciated technique.

--Rik

gardenersassistant
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Re: Testing a new (flawed) diffuser

Post by gardenersassistant »

rjlittlefield wrote:
Thu Jul 08, 2021 9:46 am
gardenersassistant wrote:
Thu Jul 08, 2021 3:03 am
I have other examples with this latest setup where the highlights on those particular beetles are still going yellow at some angles, which I don't like at all. It is complicated though, and not simply a matter of one or more of the channels clipping because that yellowing can occur even when Raw Digger says that no channel is clipping.
This suggests to me that the yellow is caused mainly by the subject. Maybe thin-film interference that suppresses blue reflection at some angles? Metallic appearance of insect cuticles is due to many layers of thin films anyway, so there is lots of room for unexpected effects.
How interesting. I assumed it was my diffusion being inadequate, so perhaps not.

It may sound strange, but I don't recall what the colour of the yellowed insects was when viewed directly. I generally only look at my subjects through the viewfinder, and later on screen. Their colours don't seem to lodge in my mind in the brief period between finding them and switching to the camera. I tried going out to the same place to find one yesterday to check, but there were none around. Perhaps they have gone for this year.
rjlittlefield wrote:
Thu Jul 08, 2021 9:46 am
Nice work with the ball-bearing test. I think it is an under-appreciated technique.
I only found out about it recently. This was the first time I used it and it was hugely helpful, so quick and easy, with instant feedback. (Must have another go at cleaning the ball bearings. I tried but it didn't make much difference. Perhaps that is imperfections in the surface rather than dirt.)
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Troels
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Re: Testing a new (flawed) diffuser

Post by Troels »

Very nice pictures with saturated colors and lots of texture.

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gardenersassistant
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Re: Testing a new (flawed) diffuser

Post by gardenersassistant »

Troels wrote:
Fri Jul 16, 2021 2:05 am
Very nice pictures with saturated colors and lots of texture.

Troels
Thanks Troels. I try to get the hues about right by calibrating the white balance of my diffusers. I generally don't touch the Saturation or Vibrance sliders, so no particular enhancement there.
Nick

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Rework and reposts of my images posted in this forum are always welcome, especially if they come with an explanation of what you did and how you did it.

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