Flash with a microscope

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pwnell
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Flash with a microscope

Post by pwnell »

I have tried using my 580EX II flash head with my Nikon E200 microscope with a 40x objective to freeze animal motion, and it works kind of... But I have a question - how do I eliminate the light from the halogen light source? Even at ISO 100, 1/200 and 40x magnification, when the view is bright enough for me to observe the bug there is still enough ambient light to be recorded on the sensor, hence causing blurry flash images.

1/200 is the maximum my 600D will sync at. Bar turning down the halogen light every time I take a photo, how do you control it?

Pau
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Post by Pau »

- If in your camera menu you can select the sync speed in AV mode, set it to 1/200, if not, use the camera in manual mode at 1/200. Otherwise in auto modes the camera try to use fill in flash. Don't use auto ISO. But because you say "Even at ISO 100, 1/200" surelly you have tried it.
- Perhaps the amount of flash light effectively entering to the microscope is too small. A picture of your microscope flash setup could help.
Pau

pwnell
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Post by pwnell »

Some background. I used to be a professional photographer, so I know my camera and equipment well. When it comes to attaching the camera to the microscope my knowledge dwindles quickly though.

The camera is set to manual mode, 1/200. The external flash is not set to high speed mode. ISO is fixed to 100.

The problem is not the flash. For now I can manage just fine to get enough illumination to create a properly exposed image using flash underneath the condenser. My problem is that with this setup, if I turn OFF the flash and take a picture there is enough light from the halogen light in my microscope to illuminate the subject so that the photo is not pitch black as it is supposed to be. Obviously I can turn off the halogen light, but then I lose the ability to see through the eyepieces.

I want to know - like in Charles setup and others, how do you preserve continuous lighting for observational purposes and use flash for photography without having to turn off the halogen lamp every time you take a photo?

yeatzee
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Post by yeatzee »

why would you need to see after each shot? Line everything up, take a couple test pictures, than when your ready start the stack with the halogen light off.

pwnell
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Post by pwnell »

Well... if I do that I can just as well use continuous lighting for the photo too. I want to use flash to freeze motion on fast swimming animals. This means I have to observe, follow it using the stage adjustments and focusing knob and take the photo the moment I have a chance. The problem is not with stationary subjects but fast moving ones.

Charles Krebs
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Post by Charles Krebs »

The only answer is to have the continuous light at a level where no image will be recorded (or at least an extremely faint image) with the continuous light source when the camera is set to its fastest sync speed. A quick test shot with no flash added can confirm this.

This tends to be most problematic in brightfield where the illumination system is most efficient. In fact, even with my flash set to its lowest power setting I still need to occasionally add some neutral density to avoid overexposure solely from the flash illumination. With brightfield you will need to turn down the microscope light considerably (or add ND), but there should still be enough illumination to follow and focus on a moving subject. (This is one reason why I suggested somewhere earlier that it may be possible to use a very fast shutter speed (1/1000, 1/2000) instead of flash in some cases with brightfield. The catch there is it may prove to be uncomfortably bright for viewing.)

With other lighting methods that "suck up" more light (phase, darkfield, DIC, crossed polarizers) it is much less of an issue.

Theoretically, with an LED as my continuous ("modeling") light it should not be too tricky to rig things up so that the LED is powered off just as the flash fires, and then goes back on. (I doubt this is practical with tungsten-halogen because of the relatively lengthy "decay" of the light from the filament).

Typically I work in a room with subdued ambient light, which allows me to work with a somewhat lower level of continuous microscope light. The camera is always on manual, set on the fastest sync speed. The flash is always used on "manual".

Planapo
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Post by Planapo »

(This is one reason why I suggested somewhere earlier that it may be possible to use a very fast shutter speed (1/1000, 1/2000) instead of flash in some cases with brightfield. The catch there is it may prove to be uncomfortably bright for viewing.)
8) How about wearing sunglasses, and adding some ND on them if required, or plain glasses with sufficient ND stuck on, or ND stuck on the eyepieces, to work around that catch?
I'm serious about this.

--Betty 8)
Last edited by Planapo on Thu Oct 06, 2011 11:23 am, edited 1 time in total.

pwnell
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Post by pwnell »

Planapo wrote:
(This is one reason why I suggested somewhere earlier that it may be possible to use a very fast shutter speed (1/1000, 1/2000) instead of flash in some cases with brightfield. The catch there is it may prove to be uncomfortably bright for viewing.)
8) How about wearing sunglasses, and adding some ND on them if required, or plain glasses with sufficient ND stuck on, to work around that catch?
I'm serious about this.

--Betty 8)
:) Very funny, but yeah that could work well for lower magnifications. Still leaves the higher magnifications with a problem - as I found that when the view is dim enough that it does not register on the camera, it is too dim to view through they eyepieces.

Charles Krebs
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Post by Charles Krebs »

I'm serious about this.
I see no reason why you could not make up eyepiece "caps" that could be readily slipped on and off the eyepieces. They could incorporate whatever ND is deemed necessary. (Seriously! 8) )
http://www.adorama.com/BW19ND4X.html
(If all you are using is brightfield, seems like it could be a reasonable alternative to setting up electronic flash).

Still leaves the higher magnifications with a problem - as I found that when the view is dim enough that it does not register on the camera, it is too dim to view through they eyepieces.
Next time I get to my microscope I'll have to check that out. My trinocular head gives an 80/20 split (camera/eyepieces) when photographing, and I do not think (other than Lomo) other "splitting" heads yield lower viewing light levels when set for photography. And yet I don't recall this being a significant problem.

pwnell
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Post by pwnell »

Mine is a 100-0-100 split. But when I say it is too dim through the eyepieces that also includes being too dim in the live view on my monitor - as it should be because you want a very close to black picture showing up in live view.

Charles Krebs
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Post by Charles Krebs »

OK, maybe we are talking about two different things. If you are using the 600D (T3i) body see my (second) post on this page:
http://www.photomacrography.net/forum/v ... e&start=75

This may be what you are referring to. The 600D is always in the "emulate exposure" mode, unlike higher end Canon bodies where this can be set to either on/off. If emulate is set to "off", for example, with a 50D body, the camera will automatically up the gain to try and provide a good live view image regardless of the exposure settings. The only way I am aware of that this can be accomplished with a 600D is to have a Canon flash attached (or the pop-up flash opened). The camera then "assumes" the flash will provide the needed light for proper exposure and increase the gain in live view to provide a viewable image.
Last edited by Charles Krebs on Thu Oct 06, 2011 12:26 pm, edited 1 time in total.

pwnell
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Post by pwnell »

That is what I do... I have the ST-2 transmitter on the camera body to trigger my 580EX II.

Charles Krebs
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Post by Charles Krebs »

I've never tried the 600D with my ST-E2. Can you confirm that it turns off the "emulate exposure " mode as is the case when the pop-up flash (or an external speedlite) is used?

pwnell
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Post by pwnell »

Charles Krebs wrote:I've never tried the 600D with my ST-E2. Can you confirm that it turns off the "emulate exposure " mode as is the case when the pop-up flash (or an external speedlite) is used?
With popup flash open, emulate exposure is off - i.e. it ignores the exposure settings and shows you the image as best it can.

With popup flash closed, and ST-E2 connected and enabled it stays in emulate exposure mode - i.e. it tries to render the exposure based on your selected exposure settings.

Charles Krebs
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Post by Charles Krebs »

If this (pop-up flash) "solves" the problem you initially asked about, you can use a dedicated E-TTL cord with your 580EX II and "exposure emulation" will be turned off when the flash is powered on.

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