My Very First 20x Stack: Chrysiridia Rhipheus (Sunset Moth)

Macro_Cosmos · Post by **Macro_Cosmos** » Tue Feb 19, 2019 8:14 am

This is the front of the butterfly (eyes up, objective down), the orange-ish region.

Taken with the mitty 20x, more information here: https://flic.kr/p/2eQaKPR

Lighting is about right, pmax stack.

Here's 100% resolution: https://farm8.staticflickr.com/7892/471 ... e348_o.jpg

It's softer than I expected, not sure if it's right or not. Personally not too satisfied, the results are acceptable however to me.

Thanks for viewing!

-- MC

rjlittlefield · Post by **rjlittlefield** » Tue Feb 19, 2019 11:32 am

I agree that it looks a bit soft.

Is this just the way it came out of camera & stacking, or has it already been digitally sharpened (and if so, how and how much)?

I'm not seeing asymmetric aberrations, like I would expect with a decentering problem.

So I'm thinking maybe vibration. It's challenging to keep things still at pixel level and 20X, with a 1.3 second exposure, even with mirror lockup or shutter delay.

For testing purposes, I suggest shooting a stack with speedlight on low power, to get exposure times in the 0.1 ms range.

One more thought: which Mitty 20X is this, the NA 0.42 normal version or the NA 0.28 longer WD?

--Rik

Adalbert · Post by **Adalbert** » Tue Feb 19, 2019 1:20 pm

Hello MC,
I have noticed something common during the tests of my Mitty 20x:
http://www.photomacrography.net/forum/v ... highlight=

But my Mitty has some problems

http://www.photomacrography.net/forum/v ... highlight=
BR, ADi

Macro_Cosmos · Post by **Macro_Cosmos** » Tue Feb 19, 2019 8:20 pm

rjlittlefield wrote:I agree that it looks a bit soft.

Is this just the way it came out of camera & stacking, or has it already been digitally sharpened (and if so, how and how much)?

+120 in Capture One Pro

rjlittlefield wrote: I'm not seeing asymmetric aberrations, like I would expect with a decentering problem.

Yeah I agree, decentering in objective lenses can be weird though. From asymmetric aberrations all the way to overall softness, depending on how bad it is.

rjlittlefield wrote: So I'm thinking maybe vibration. It's challenging to keep things still at pixel level and 20X, with a 1.3 second exposure, even with mirror lockup or shutter delay.

For testing purposes, I suggest shooting a stack with speedlight on low power, to get exposure times in the 0.1 ms range.

At 10x, I can go all the way to 5 seconds. Vibrations is kind of a weird issue, I don't own any speedlights anymore. I do have an Einstein E640 studio strobe from PCB, going to try that later so see what happens.

rjlittlefield wrote: One more thought: which Mitty 20X is this, the NA 0.42 normal version or the NA 0.28 longer WD?

It's the 0.42 version, not SL. The SL version has the same NA as a normal 10x mplan, not sure why anyone would buy that for photomacrography, might as well pull the 10x to 20x via a 400mm tube lens.

Adalbert wrote:Hello MC,
I have noticed something common during the tests of my Mitty 20x:
http://www.photomacrography.net/forum/v ... highlight=

But my Mitty has some problems
http://www.photomacrography.net/forum/v ... highlight=
BR, ADi

Thanks for the links, I'll have a look.

Thanks for the help.

rjlittlefield · Post by **rjlittlefield** » Tue Feb 19, 2019 9:45 pm

Macro_Cosmos wrote:
rjlittlefield wrote:I agree that it looks a bit soft.

Is this just the way it came out of camera & stacking, or has it already been digitally sharpened (and if so, how and how much)?
+120 in Capture One Pro.

Thanks. Unfortunately I don't speak Capture One so I don't know how hard that is.

I did pull your full-size image into Photoshop and hit it with an Unsharp Mask at 300% and 1.5 pixels. That made visible a lot of what looks like real detail at fine scale.

Remember that at NA 0.42 and 20X, you're running at effective f/23.8. Even using lambda = 0.55 micron, diffraction would still put you at MTF=0 at 13.1 microns/cycle, MTF=39% at 26.2 microns/cycle. It takes pretty hard sharpening to compensate for that much softening.

The SL version has the same NA as a normal 10x mplan, not sure why anyone would buy that for photomacrography, might as well pull the 10x to 20x via a 400mm tube lens.

I agree. But I've seen it done, so I thought I should ask.

--Rik

Macro_Cosmos · Post by **Macro_Cosmos** » Tue Feb 19, 2019 11:42 pm

rjlittlefield wrote: I did pull your full-size image into Photoshop and hit it with an Unsharp Mask at 300% and 1.5 pixels. That made visible a lot of what looks like real detail at fine scale.

Remember that at NA 0.42 and 20X, you're running at effective f/23.8. Even using lambda = 0.55 micron, diffraction would still put you at MTF=0 at 13.1 microns/cycle, MTF=39% at 26.2 microns/cycle. It takes pretty hard sharpening to compensate for that much softening.

I see, the NA is a limiting factor. I'm using a 36MP D810. Still a pretty high MP body by today's standards. An HR objective would do really well... if one can even find it.

As far as both my friend (he gave me the objective) and I are aware, there's no decentering which is always a relief. I had to take the objectives on a 10-hour-flight. I think I did a good job in protecting them. Potentially, lighting can be a problem as well. I'll try different lighting methods. I also ran a stack on a Papilio genus butterfly, the results were just bad. I'm seeing the leap from 10x to 20x as a major challenge to my skills...

Thanks for the help! I might upload the .tiff file somewhere. The non-processed version is even softer.