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Mounting *very* small beetles for macro stacking
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rjlittlefield
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Joined: 01 Aug 2006
Posts: 18246
Location: Richland, Washington State, USA

PostPosted: Sun Dec 03, 2017 12:24 pm    Post subject: Reply with quote

Beatsy wrote:
I think I need a smaller ping-pong ball (or equivalent) to get the exact lighting I'm after. Struggling to apply much light from the front with the shorter working distance of 20x and 50x mitties. Something around 15mm diameter should help that too. That blimmin' inverse square law plays havoc with blown highlights when you're using such small subjects.

I'm confused. Looking at the images, it appears to me that you have a lot of light on the front, not so much elsewhere. I can understand how that could be due to inverse square law if the light source were small and close, but then the solution I'm imagining would be to use a larger diffuser so that the subject could be surrounded by a uniform sphere of light (except for the inevitable "black hole" of the lens aperture). I don't understand how using a smaller diffuser is going to help, unless you're looking to increase the distance between the outer and inner layers of your diffusion system.

Can you explain in more detail how you're thinking about this?

--Rik
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Beatsy



Joined: 05 Jul 2013
Posts: 911
Location: Malvern, UK

PostPosted: Sun Dec 03, 2017 1:14 pm    Post subject: Reply with quote

rjlittlefield wrote:
Can you explain in more detail how you're thinking about this?--Rik

I can't put the subject far enough inside the ping pong ball due to the shorter working distance of the higher mag Mitties. The hole in the front of the ball is smaller than the objective barrel, but if I make it larger (so the objective can move closer) there is less material facing the front of the subject. A mini catch 22.

As it is, the specimen is closer to the front than it is to the top and sides of the ball so light I *do* get on the front is too bright compared to the sides. I tried increasing light on the sides but it made no noticeable improvement as it's difficult to light small sections of the ball without re-introducing specular highlights. Note: I removed the outer diffuser dome to try this so I could "spot aim" the lights better - it had no effect at all with the outer diffuser in place (for obvious reasons).

Anyway, there's not much science in my musings, but if I can just keep the specimen mounted centrally within the ball, I believe it will work as well as previous lower mag stacks where I had more success with lighting. I had the specimen further back in the ping pong ball for all of those, and this is why I think a smaller ball will help here. The subject can be placed centrally and everything else should go swimmingly - as before. Or not... Smile
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