lighting choices for microscope objectives?

[CarlW]

My recent post requested information about increasing my magnification levels without losing resolution. Much of the information suggested moving towards microscope objectives. I have begun to research this possibility, but have a concern that light will become and issue. I currently do not think flash is appropriate for my application at this time. I do not know if these rather small lenses are capable of letting in enough light to use multiple LED work lights to illuminate the subject that I currently use. My plans involve capturing subjects from dozens of angles and using photogrammetry software to create a 3D mesh of the surface of my macro subject. This means photos numbering perhaps 2000 plus photos per subject. I'm not sure I can tolerate that many flash cycles. What are my lighting possibilities with these objectives?

[gremlin]

I've recently taken this with a Lomo 9x objective lit by 2 LED lights 60 frame stack

[ChrisR]

Carl you'll just have to light the subject "from everywhere". IE diffuse like crazy. Maybe a light tent with a small hole for the lens. Don't start with anything too shiny!

[mawyatt]

Carl,

I've shot many sessions with 2000 or more images (S&S Sessions) using strobes. With the right strobes, timing and setup this isn't an issue.

Best,

[CarlW]

With my current 100 mm macro lens with extension tubes and or teleconverter I have the aperture spring wedged open to allow as much light as possible. With 3 fairly bright LED lights inches from the subject I am able to shoot at 1/160th. I can only imagine a microscope objective is going to let in way less light. Are there any estimates of how much slower my shutter speed would need to be with a microscope objective if my current lighting was not upgraded? If I was to venture into a microscope objective it will likely be a low power 5x-10x, if that makes any difference.

[Chris S.]

Carl, this is a different fellow named "Chris" responding--Chris S., not ChrisR.

Are there any estimates of how much slower my shutter speed would need to be with a microscope objective if my current lighting was not upgraded? If I was to venture into a microscope objective it will likely be a low power 5x-10x, if that makes any difference.

I have a number of objectives in the 5-10x range, and their effective f/stops run from f/17-f/20. (There is math for determining this, but to keep this conversation at the practical level, as well as the new-comer level, I'll leave it out.)

So for a decent view of your potential lighting needs, you might try shooting your macro lens at effective f/16, f/22, and halfway between these two settings. This would give you a decent idea of the shutter speeds you'd need for a microscope objective in the range you specified. Please note the important word "effective" I used when describing the aperture setting for your macro lens. As you likely know, effective f (the actual f/stop your lens is shooting at) equals nominal f (the f-stop your lens is set at) only when focused at infinity. As you focus close, into the macro range, effective f decreases substantially. If you're shooting a Nikon system, your camera will report effective f; if a Canon system, it will report nominal f. For other systems, I'd have to look it up. Regardless, this paragraph contains enough search terms that with a bit of searching, you can determine effective f for your system when your macro lens is extended to, say, 1:1. (And I mean no insult if you already know these concepts well!)

You'll note that I've excluded extension tubes and teleconverters from configuration suggested above. Their effects can be calculated as well, but can add confusion.

As a bottom line, it appears that your photographic goals are best served with a 5x or 10x microscope objective, or both. If this is the case, I'd suggest you purchase one or both of these optics, and work out the lighting afterward. Lots of us at this forum work with lenses like this, and have figured out how to provide sufficient lighting without undue hardship.

As to hints on providing necessary light, let me offer the following: If you have a very stable rig and studio, such that very long exposures have no blur, feel free to take, say, eight-second exposures, as I do. (I have plenty of light for much shorter exposures, but prefer long exposures to minimize the effect of shutter-induced vibration.) Or if your equipment or studio are prone to vibration, go the opposite direction and shoot with powerful flash of brief, intense duration. Neither approach is terribly difficult--both approaches have been very well worked out in our forum. So you can just get your lenses, and deal with lighting later.

Cheers,

--Chris S.

Edit to add: This thread probably fits better in the "Macro and Micro Technique and Technical Discussions" forum. Any member of the admin team can move this thread once everyone has seen this message.

[Lou Jost]

I can only imagine a microscope objective is going to let in way less light.

You've said this a couple of times, but it is not usually true. Read up on numerical aperture (NA) and the formulas to convert it to f-stop equivalents.

Here's a good start, with a table connecting f stops and NA:
https://www.edmundoptics.com/resources/ ... e-setting/

[CarlW]

My concern about letting in less light than my normal camera lens set up, is based on the inside diameter of my aperture fully open is likely bigger than the outside diameter of the microscope objective. I am still learning, so will continue to investigate. I am hesitant to upgrade one item, if two or three other investments will be needed to made things work. For me, waiting until I can assemble all the pieces needed is preferred to figuring it out one component at a time. Thanks to all for the suggestions.

[Lou Jost]

But you've surely noticed that almost everyone here uses microscope objectives for m much bigger than 4x. There's a reason. Did you learn about NA at that link I gave?

[ChrisR]

is based on the inside diameter of my aperture fully open is likely bigger than the outside diameter of the microscope objective

That's Not a relevant parameter. What matters is the angle of the cone in which light comes from a point on the subject into the lens.

The camera lens would be far away, so it's a narrow angle.
You get the widest cones with microscope objectives, which are highest "NA" - as Lou says.

[BugEZ]

Carl wrote “to create a 3D mesh of the subject...”

Did you see this thread? I dabbled in this several years ago.

http://www.photomacrography.net/forum/v ... ud&start=0

I have seen where DOD funded scientists have mapped insects with similar techniques.
https://www.ncbi.nlm.nih.gov/pubmed/27655343

Keith

[CarlW]

I had not seen that discussion, and your work. Being an artist type a lot of the discussions on this forum are above my head. I can imagine the concept, but following all the technical aspects is a challenge. While the standard photogrammetry process works fairly well it seems like the depth map information from stacking has a lot of potential to aid building 3D models. It looks like there are professional systems that have this process figured out. I would like to try it out at some point if the technology becomes more accessible.