Sharpness issue , Please help.

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Janak Choudhary
Posts: 8
Joined: Thu Sep 28, 2017 3:08 am
Location: Jagadhri,Haryana,India

Sharpness issue , Please help.

Post by Janak Choudhary »

I m struggling with sharpness issue while shooting with Nikon 10X objective . the image well focused in the center but soft in the middle n again focused at periphery. A patch in between is soft or rather out of focus. the set up is ,like this ,
Canon 6d m2, canon bellows fully extended ,raynox 150 reversed ,iris aperture usally fully opned,nikon 10x objective. wemacro rail ,Yongnou twin flash,styrofom cup diffuser ,10 micron step, abuot 167 shots, Zeren stacker.
the set up is mounted on heavy base n table, floor cemented, flash at 1/128.rear curtain synch.

Pic 1- is slightly cropped to remove unwanted portion from image , unprocessed,resized to less than 300 KB.

Pic 2- is part of image showing central well focused area n adjoining unfocused area. This was cropped in PS - area marked with marquee tool -Image -crop and than resized to less than 300 kb.

Pic -1 ,Image
Pic-2,
Image

what is the problem here , what wrong am I doing .

Your valuable suggestions are welcomed.
canon 1DX mk II .6d markii,7DmkII,Canon 100mm macro,wemacro rail, nikon cfi 10X OBJECTIVE.Amscope 4X ,canon bellows FL,Raynox 250

ChrisR
Site Admin
Posts: 8668
Joined: Sat Mar 14, 2009 3:58 am
Location: Near London, UK

Post by ChrisR »

First, welcome to the forum!
what wrong am I doing .
Not much, as far as I can see. If the flash is connected to the camera , I think it'll force the mirror to cycle, so you could leave somewhat lnger than 128th. Say 2 seconds, if the room is dim. I don't suspect that's the particular problem though.

10µm should be ok,..
I can only say try something else - something flatter, on an angle, maybe, like a both wing.

You shouldn't hit a problem with the forum upload limits. At the max of 1024 wide, if you select your JPG quality you can get different pixel counts, then 300 kB is enough, though the margin isn't huge.
In Photoshop-like software, Export for web and devices, sometimes marked "legacy" works well.
Often for fine analysis, it's better to select a crop of a region of the original frame and post that, sized so you don't have to reduce it.

I will ask, though it probably isn't an issue, which alignments in Zerene are you using On or Off?
Chris R

Chris S.
Site Admin
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Joined: Sun Apr 05, 2009 9:55 pm
Location: Ohio, USA

Post by Chris S. »

Janak, let me second ChrisR in welcoming you to the forum! :D (I’m a different fellow named "Chris.")

I suspect that the reduced resolution in the center of your image is due to increased diffraction in that region of the image. This may sound strange, because diffraction is normally thought of as dependent on the aperture of the lens, which is the same for the entire image. But really, diffraction is dependent on the amount of the lens that you actually use, and this can vary from one portion of your subject to another. If a region of your subject reflects light through only part of the lens, that region will be rendered with lower resolution (more diffraction), much as if you had used an iris to stop down the lens when photographing that region. We’ve come to call this phenomenon the "utilized aperture" effect, and a Google search for "utilized aperture site:photomacrography.net" will bring up long and technical discussions, should you have interest.

Why do I think this? Note that below the antennae, there exists what looks like a reflection of the antennae. If so, the area reflecting the antennae has a mirror-like quality. And the more mirror-like a portion of a subject is, the more likely it is to bounce light into only a limited portion of the lens and induce utilized-aperture effects, such as reduced resolution.

To deal with this problem, an approach that often works is to increase the apparent size of the light source, as seen by the subject. Even though you’ve diffused your twin-light through a polystyrene cup, the highlights on the compound eye show that the light is still quite directional. To resolve your issue, I’d recommend finding some way to spread out the illumination considerably more. (You might try putting more space between your lights and the diffuser—so that a greater surface area of the diffuser is lit—or try bouncing the light, rather than shining it through a diffuser.

This said, I don’t shoot studio insect portraits, and we have members who do so regularly. A practiced eye may find me wrong, and I am prepared to stand corrected.

Cheers,

--Chris S.

Janak Choudhary
Posts: 8
Joined: Thu Sep 28, 2017 3:08 am
Location: Jagadhri,Haryana,India

Post by Janak Choudhary »

Thanx ChrisR, for your Valuable input. This will definitely help me in improving my skill. I will try different setting of flash next time . In Zerene I am processing both alignments and use the result of best one .
Thanx once again.
canon 1DX mk II .6d markii,7DmkII,Canon 100mm macro,wemacro rail, nikon cfi 10X OBJECTIVE.Amscope 4X ,canon bellows FL,Raynox 250

Janak Choudhary
Posts: 8
Joined: Thu Sep 28, 2017 3:08 am
Location: Jagadhri,Haryana,India

Post by Janak Choudhary »

Thanx Chris S, for warm welcome , I know both of you as our site Admin.

Thanks also for in depth analysis of my problems , will go through the diffraction part and while performing the next stack will consider all points suggested by you.
Thanks for help.[/quote]
canon 1DX mk II .6d markii,7DmkII,Canon 100mm macro,wemacro rail, nikon cfi 10X OBJECTIVE.Amscope 4X ,canon bellows FL,Raynox 250

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