Exposure Control With Finite Objective

[Deanimator]

This is probably a stupid question, but one for which I've seen no discussion anywhere.

When using a finite objective, what's the best way to control exposure?

Since there's no diaphragm, it would appear to leave only:

• shutter speed
• ISO
• intensity/duration of illumination (eg. flash power).

I'm using Amscope 4x and 10x objectives on bellows, with a chipped adapter on a Canon T4i.

For illumination I have the option of flashes, Jansjo LED lamps, and 300w equivalent CFLs.

I was surprised that I didn't find any actual discussion of this yet.

[ChrisR]

Either a vibration-free shutter or flash/lighting duration I guess.
I've rarely moved off base iso. Outside in the wind, or for fine exposure control where flash increments are whole-stop.

[Deanimator]

Either a vibration-free shutter or flash/lighting duration I guess.
I've rarely moved off base iso. Outside in the wind, or for fine exposure control where flash increments are whole-stop.

Thanks.

It took me about three hours of searching in between support calls, but I found a couple of references in sites devoted to cameras attached to microscopes. They cited shutter speed.

After a brief hiatus for still life (and constructing my still life rig), I'm working my way back to the 10x Amscope.

I'm trying to do things in a systematic and logical way this time, now that I'm not building a camera rig and learning technique at the same time.

I've got my subject rig almost done, minus a better way of mounting the diffusion material. I hope to get some better results with the 4x and 10x.

[Lou Jost]

I think no one discusses this because there are so many different ways to do it. Finite and infinite objectives are the same in this regard, there is nothing special about them (we usually don't stop down the tube lens to control exposure, for reasons that Rik has explained on this forum).

Shutter speed is the obvious one for continuous light, but for flash you can move the lights, add diffusers, etc. If you need very fine control you can use cross polarization and vary the degree of crossing, though you will lose at least half the light with this technique.

[perdu34]

I think I'm just to parrot the other comments but I change the amount of light and keep all other variables as constant as possible.

Shutter speeds of 1/160s will keep vibration to a minimum and allow flash sync with most cameras. Using shutter up and a long enough pause between movements and actually taking the image helps too.

[Deanimator]

I think I'm just to parrot the other comments but I change the amount of light and keep all other variables as constant as possible.

Shutter speeds of 1/160s will keep vibration to a minimum and allow flash sync with most cameras. Using shutter up and a long enough pause between movements and actually taking the image helps too.

Coincidentally, I figured out how to do mirror lockup with the Wemacro this morning.

I'm running some tests with flash and foam cup diffuser mounted on the objective.

[RobertOToole]

This is probably a stupid question, but one for which I've seen no discussion anywhere.

When using a finite objective, what's the best way to control exposure?

Since there's no diaphragm, it would appear to leave only:

• shutter speed
• ISO
• intensity/duration of illumination (eg. flash power).

I'm using Amscope 4x and 10x objectives on bellows, with a chipped adapter on a Canon T4i.

For illumination I have the option of flashes, Jansjo LED lamps, and 300w equivalent CFLs.

I was surprised that I didn't find any actual discussion of this yet.

My advice.

To vary the amount of light hitting the sensor to control exposure at base ISO, you can vary the amount of light with shutter speed or flash power.

One big mistake people make, even experienced photographers do this sometimes, is that they choose shutter speed to control exposure. If they set the speed near ambient exposure, this can cause ghosting which can smear fine details. To eliminate ghosting you need to use a fast shutter speed, I use 1/160-1/200th.

So I prefer to use flash power to control the exposure. Works great and there is never a chance of ghosting.

Robert

[Deanimator]

One big mistake people make, even experienced photographers do this sometimes, is that they choose shutter speed to control exposure. If they set the speed near ambient exposure, this can cause ghosting which can smear fine details. To eliminate ghosting you need to use a fast shutter speed, I use 1/160-1/200th.

So I prefer to use flash power to control the exposure. Works great and there is never a chance of ghosting.

Robert

Last night, I did an around 127 image stack of the end of a broken house key.

I first tried 1/200, but was getting the shutter in the picture. I switched to 1/160 and I'm very happy with how the stack turned out.

[ChrisR]

That's useful info, I though most cameras were OK at 1/200th. Which model is that?

[Deanimator]

That's useful info, I though most cameras were OK at 1/200th. Which model is that?

• Canon T4i
• Amscope 10x objective on bellows
• Amazon Basics manual flashes
• Wemacro rail

I think it has to do with the fact that they're manual flashes. The controls allow you to configure ETTL flashes for 1/200.

The Amazon flashes are cheap enough that it's not a tragedy if one of them fries because of a 100+ image stack. The Sigma or Flashpoint ETTL flashes? Not so much.

I eventually plan to buy a couple of the Flashpoint radio strobes. I was set to buy a couple when they were $90, but I wanted to wait until my employment was nailed down. Then they were on back order. I'll probably buy them in the next month or so.

[Macrero]

Which 10X model do you have? The one I tested has extremely small image circle and performance is awful even on m4/3 sensor.

- Macrero

[Deanimator]

Which 10X model do you have? The one I tested has extremely small image circle and performance is awful even on m4/3 sensor.

- Macrero

https://www.amazon.com/gp/product/B01G4 ... UTF8&psc=1

It's not easy to use, but under the right conditions, it gives good images:

[Macrero]

Does not look as bad as the one I tried, but even at that size resolution seems poor and coverage is clearly far from perfect. The 4X works surprisingly well, but none of the chinese 10X objectives I tried are worth using on camera. If you work with finite system you'll get much better quality off of a Nikon CF finite objectives: M (BD) Plan 10 or even E Plan 10 LWD, CF N Plan 10 (coverage is a tad worse), etc.

Best,

- Macrero

[Deanimator]

Does not look as bad as the one I tried, but even at that size resolution seems poor and coverage is clearly far from perfect. The 4X works surprisingly well, but none of the chinese 10X objectives I tried are worth using on camera. If you work with finite system you'll get much better quality off of a Nikon CF finite objectives: M (BD) Plan 10 or even E Plan 10 LWD, CF N Plan 10 (coverage is a tad worse), etc.

Best,

- Macrero

I have both the 4x and 10x Amscope objectives.

While I find that the 4x is easier to use and gets better results, the 10x was an affordable experiment. I paid for both together (plus the bellows and relevant adapters) less than I'd pay for a lot of used name brand objectives.

I'm just getting started in using microscope objectives and didn't want to immediately sink a lot of money into something that's pure amusement for me. I didn't want to take a risk on a used objective when I have zero experience with them. The odds of me getting a piece of junk were just way too high for a beginner.

[Macrero]

While I find that the 4x is easier to use and gets better results, the 10x was an affordable experiment. I paid for both together (plus the bellows and relevant adapters) less than I'd pay for a lot of used name brand objectives.

I'm just getting started in using microscope objectives and didn't want to immediately sink a lot of money into something that's pure amusement for me. I didn't want to take a risk on a used objective when I have zero experience with them. The odds of me getting a piece of junk were just way too high for a beginner.

Understandable. Those are cheap, so not a big loss either. Though Nikon finite objectives are tough optics, you'd have to have a very bad luck to get a bad/damaged one.

On the topic, I am guessing you shoot in Live View which acts basically as EFSC, how the "shutter shock" impacts image then?

- Macrero