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ND filters for micro video?

 
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dragonblade



Joined: 18 Oct 2014
Posts: 140

PostPosted: Thu Jan 11, 2018 8:10 am    Post subject: ND filters for micro video? Reply with quote

With regards to afocal photography with microscopes, I seem to read a mix of user experiences concerning brightness levels. Some say that for photography, the light levels we deal with through microscopes is very low and must compensate with slow shutter speeds or flash etc. However, Ive also heard at least one individual say that ND filters may be required which suggests a very high level of image brightness.

Out of curiosity, do any of you video shooters use ND filters with microscopes in afocal setups? Considering that you'd be shooting with the aperture wide open and 1/50th (for 25fps) or 1/60th (for 30fps), I'd think that ND filters might be commonplace for microscope videography.
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Pau
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Joined: 20 Jan 2010
Posts: 4278
Location: Valencia, Spain

PostPosted: Thu Jan 11, 2018 12:24 pm    Post subject: Reply with quote

This depends of the amount of light reaching the sensor, different factors involved
- at higher magnification you have much less light
- the condenser and objective NA
- the power of the light source, halogen and old incandescent lamps can go from 10W to 150W...
- illumination technique: cross pol, DF, oblique, DIC and even Phase cut off a lot of light
In principle afocal or not is irrelevant.

In most cases for video you likely don't want ND filters. Better test yourself with your camera and microscope.

ND just cut off light, you want them when the minimum light intensity is excessive like at BF with low power objectives and a powerful lamp or with some LED arrangements or when you want to take long exposures to avoid camera induced vibrations for photo.
They are often recommended with incandescent lamps because the color temperature changes with the power and so the light becomes reddish at low power, this issue is almost inexistent with LEDs but some LED arrangements flicker when dimmed at lower than maximum power.
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Pau
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dragonblade



Joined: 18 Oct 2014
Posts: 140

PostPosted: Thu Jan 11, 2018 10:42 pm    Post subject: Reply with quote

Pau wrote:
Better test yourself with your camera and microscope.



Will definitely do. That was the plan. I am using bright field but will probably use the 40x objective most of the time for video recording. Lighting provided by this LED source on my microscope is very uneven with the lower power objectives.
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