Simple but good light (for nearly everything) at last...

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Beatsy
Posts: 1748
Joined: Fri Jul 05, 2013 3:10 am
Location: Malvern, UK

Simple but good light (for nearly everything) at last...

Post by Beatsy »

I'd like to say I experimented for years (which I have) and discovered *the* key ingredients for a simple-to-use yet versatile lighting setup that delivers consistent high-quality results.

But the bit about directly identifying key ingredients isn't quite true. Rather, I tinkered with lighting variables each and every time I put a new specimen in the rig and gradually eliminated hundreds of things that didn't work so well. I had to eliminate some of them several times. Or (more often) I eventually recognised and abandoned fiddly, slow and difficult approaches that gave little or no benefit.

After all those years eliminating the inefficient, impractical and ugly, what's left is so simple and frankly "bleedin' obvious", it's almost embarrassing! So I won't crow about it too much, but here's my latest and best-to-date lighting fixture for general use on my macro rail. I'm really pleased with it. It supports a good range of objectives (2x Minolta Dimage and 5x-20x Mitties) and the subjects I shoot with them. This working prototype needs tweaks (there will be a "production" version and a smaller clone for my 50x Mitty) but the fundamentals are all there so I think I'm done tinkering with extreme-macro lighting - for a while.

Here's the shader - a ping-pong ball, with holes and black background, held a little way inside a Godox dome diffuser (in front of a hole the objective looks through). Cutouts and holes in the diffuser are to suit my specimen holder and the FoV range of the objectives supported. The Godox dome allows for internal bounce light and "through" lighting as pictured, but I probably won't use through-light any more because bounce makes *much* more efficient use of available light. The inner surface will be painted to make it opaque and bounce more light back. Bits of white paper do that (at the front) in this pic.
shader pic 1.jpg
The view from the objective side. The 20x Mitty can be further back from the shade, but working distance means the specimen would have to be closer to the inside-front of ping pong ball which reduces the light bounced "face on" to the specimen. A smaller version will fix that - but the light-tight short tube that attaches the ping-pong ball to the dome ensures enough space for some light to get in as is - so the 20x is just about workable here whereas the 50x is not. Note the microscope mirror (from a cannibalised Wild Heerbug scope) bottom right. We'll see that again.
shader pic 2.jpg
I used a spare Prior probe-holder for x,y,z adjustment of the shader and a means to quickly swing it over (or off) the specimen - as shown here. Works very nicely too.
Shader pic 3.jpg
The view of the shader from underneath (swung fully over).
shader pic 4.jpg
What the objective sees - a black hole with a brightly lit subject in it (not present here). No light leaks, so any number of lamps can be waved around with abandon at the back and bounced around in any direction. None will ever enter the objective directly unless pointed up from underneath through the specimen mount hole - and that never happens.
Shader pic 5.jpg
To setup the required lighting, I simply swing the shader over a mounted specimen. Note: the mirror swings in so I can see the specimen and avoid banging the shader into it (a distressingly frequent problem with loose, ad-hoc setups before).
shader pic 6.jpg
Lights last. Here just two Schott goosenecks positioned as shown. Most light is bounced off the front of the main dome and onto the ping-pong ball. But one of the diffuse spots is allowed to directly "graze" the ping-pong ball, creating a separate, brighter spot from that direction. This setup is like having two spot lights and two big softboxes, all adjustable by simply pointing the goosenecks in the right direction.
shader pic 7.jpg
And finally, first light - wing detail on the fly - a sometimes-tricky, metallic Greenbottle. I used a 10x mitty pushed down to 6.75x for this (not the 20x shown in the pics above) but lighting was as shown. RAW images were converted to tiff (linear profile with no colour correction) and stacked in Zerene, no retouching. Simple exposure and contrast adjustments produced this result. Square cropped from an APS-C (crop mode) capture. The foggy bit was an OOF area behind the wing (seen in focus through the wing) that had nothing behind it to "replace" the fog when it came into focus. My bad - but I'm well happy with the quality for such simple lighting.
shader pic 8.jpg
Happy to answer any Qs.

rjlittlefield
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Re: Simple but good light (for nearly everything) at last...

Post by rjlittlefield »

Very interesting, as always!

I've added this thread to the list in the FAQ.

That Prior probe-holder is new to me. Searching Google on those terms finds nothing that looks like it. Can you suggest where we could go to find more info or units?

--Rik

joshmacro
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Location: New York

Re: Simple but good light (for nearly everything) at last...

Post by joshmacro »

Very informative Beatsy. What type of paint did you use on the ping pong ball?

Beatsy
Posts: 1748
Joined: Fri Jul 05, 2013 3:10 am
Location: Malvern, UK

Re: Simple but good light (for nearly everything) at last...

Post by Beatsy »

rjlittlefield wrote:
Sat May 08, 2021 4:40 pm
...That Prior probe-holder is new to me. Searching Google on those terms finds nothing that looks like it. Can you suggest where we could go to find more info or units?
Search for 'prior micromanipulator' in google images (no quotes). That brings up various examples, including this model. and is a good basis for further searching. These are most often used as manipulators in their own right (cell injection etc), but also as a coarse adjustment base for smaller, finer manipulators. That's what I ended up "collecting" things like this for, but they proved them selves as very stable "long-reach" specimen holders in ad-hoc setups, and for many other things too (holding specimens at various angles under a stereo when cleaning and arranging legs, for example).

The one used here was destined for the spares box after I found a better, low-profile holder for a hydraulic manipulator head. But it never makes it in there because I always find *some* other useful function for it - though this most recent use might become a semi-permanent one.

Edit: I should add that if I didn't already have the Prior thingy, I certainly wouldn't buy one just for this task. Too expensive, and massive overkill in the precision it offers (said nobody on PMN, ever). The mechanically minded could easily fashion a homebrew equivalent - or cobble other parts together - e.g. fit an x,y stage mechanism to the dome and attach that to the end of a Noga stand arm (for the swing over function). Not as precise, pretty or as nice to use, but it will competently serve the same function. Guess how I know that... :D
Last edited by Beatsy on Sun May 09, 2021 1:03 am, edited 3 times in total.

Beatsy
Posts: 1748
Joined: Fri Jul 05, 2013 3:10 am
Location: Malvern, UK

Re: Simple but good light (for nearly everything) at last...

Post by Beatsy »

joshmacro wrote:
Sat May 08, 2021 6:32 pm
Very informative Beatsy. What type of paint did you use on the ping pong ball?
Happens to be the Stuart Semple "Black 2.0" in this case, but it's not particularly important. I often stick small circles of coloured card, flocking, white paper, or even small printed images in the back to change the background.

I tried leaving the back of the ping-pong ball open for a while, propping card or similar behind for background colour. The idea was to allow lighting from the rear for rim-lights etc, but it just became a liability. Always letting stray light into the objective when I didn't want it to. It also allowed ambient light to affect exposures if I wasn't careful (e.g. walking past and blocking ambient while stacking was running). Fully enclosed like this works much better and more consistently overall.

micro_pix
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Location: Southampton, Hampshire, UK

Re: Simple but good light (for nearly everything) at last...

Post by micro_pix »

Thanks for sharing this very elegant solution! I must admit your precision diffusion-positioning-device made me smile.

Dave

Beatsy
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Joined: Fri Jul 05, 2013 3:10 am
Location: Malvern, UK

Re: Simple but good light (for nearly everything) at last...

Post by Beatsy »

Another example "in use", but at the low end of the mag range supported. Shot with A7riv and a DImage scanner lens at 2x onto APS-C (it can cover full frame too, but this subject was too small to warrant it).

Again, nothing special lighting-wise. I just dropped the shader over, set the lights for diffuse bounce from (mostly) front and top/left then moved one light to also graze a little catch light on the ping-pong ball (top right) to raise subtle highlights in the more shaded areas. A pretty good default look IMO - especially given the ease of use and quick setup.
badhair.jpg

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