Best Kelvin Temperature For Microphotography

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lonepal
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Best Kelvin Temperature For Microphotography

Post by lonepal »

Hi;

I digged up internet and found lots of comments but there is not a common decision on this.
Now I use warm white led lights at around 3000K (Ikea Jansjö).
My idea is using the Kelvin Temperature as near as dayligh temperature.
I plan to change my lighting system but I am worried if it worth it.
I mean I wonder if changing the leds from 3000K to 5500K changes anything other than white balance seeting on camera :)

What is you idea and which Kelvin Temperature is/are your leds/other?

Thanks for comments.
Regards.
Omer

ChrisR
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Post by ChrisR »

LEDs tend to have a big peak in output at the blue end of the spectrum - check some data sheets.
A Black Body at a particular Kelvin temperture "should" have a standard shaped envelope of the visible spectrum and beyond. LED outputs are sort-of averaged by manufacturers to give a number.

Look at the Color Rendering Index of the light source (if you can find it).

You can correct for a Color Temperature in the camera, but you can't do much about the CRI.
Chris R

lonepal
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Post by lonepal »

Hi Chris;

Do you use LEDs or other?
Regards.
Omer

ChrisR
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Post by ChrisR »

Flash mostly, to stop vibrations. Though not much of anything recently :( .


If you search on CRI you should find plenty of references on the forum.
Look at what member fotoopa has done :)
Chris R

lonepal
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Post by lonepal »

Hi Chris;

I know what he did :)

I just want to know how the Kelvin Temperature of the light effects our photos and which range is optimal for microphotography.
Regards.
Omer

ChrisR
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Post by ChrisR »

I am not advanced enough for it to make a difference! As long as the camera is set correctly - sometimes by custom while balance.
If you search on metamerism, you will find some examples where it was important. That's subject-specific. Artificial fibres can look quite different.
Chris R

Pau
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Post by Pau »

I mean I wonder if changing the leds from 3000K to 5500K changes anything other than white balance seeting on camera
Yes, it does.

If you look at the spectrum of different "white" LEDs there is a prominent blue* peak (the primary emission of the LED) that also serves to excite the fluorescent dyes to produce the other wavelengths. High K values LEDs have this peak much more prominent over other wavelengths than in lower K LEDs

This is why high CRI models never have very high color temperature.

In the other hand, auto WB is poor in most digital cameras at low color temperature although is always better to set custom WB.

For my microscope illuminators I've found a good compromise with the well powered and inexpensive Cree XML T6 "Neutral White" 4000K , much better than other higher temperature chips formerly tested.
Of course there are better color optimized LEDs for more exigent people...

You said "Microphotography", do you want to use it inside a microscope illuminator or as light source for macro? I ask it because for the first application there are other constrains like the chip size, not present or less important for macro


*in few new types the excitation peak is violet
Pau

zzffnn
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Post by zzffnn »

Omer seems to be more interested in marophotography than microscopy?

Pau said it better than I can.

Yes, 4000k is usually a safe bet for good CRI. I have seen it to be the case at least twice. Better still, look at the LED's emission spectrum and avoid those with too much blue and too little red/green (and compare to a typical halogen emission spectrum).

I usually prefer camera's custom Kevin temperature, over auto white balance, when using LED for microscopy. Using microscope eyepiece image as reference, photos made with Kevin temperature white balance looks closer to visual view than auto white.

When I started, I mistakenly picked a 40w 5000k LED for its cool white color and slightly higher output. Its CRI is only 80. Its 4000k sibling has a bit better CRI and more green output, which is actually a better choice, at least for microscopy.

And yes, cool white is usually around 5000k, and neutral white around 4000k, per many LED manufacturers.
Selling my Canon FD 200mm F/2.8 lens

75RR
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Post by 75RR »

For my microscope illuminators I've found a good compromise with the well powered and inexpensive Cree XML T6 "Neutral White" 4000K , much better than other higher temperature chips formerly tested

Hi Pau, can you post a link to the pdf, I can't find a Cree XML T6 at 4000k in the literature I have.
Zeiss Standard WL & Wild M8
Olympus E-p2 (Micro Four Thirds Camera)

Pau
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Post by Pau »

Glen, here you have:
http://www.cree.com/led-components/medi ... ampXML.pdf
from:
http://www.cree.com/led-components/prod ... xlamp-xm-l

The "T6 4000K" I bought will be (I guess) the 3700 K - 5000 K with CRI 75 that doesn't seem high but actually works well for me.
Chinese ebay sellers are not good with accurate info! :roll:
Pau

lonepal
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Post by lonepal »

Hi!
Thanks for the replies.

I have mitty 10X and 20X lenses and I use them for macrophotography.
I have no microscope so sorry for microphotography Word :)

I use 2 ikea lamps which are at 3000K temperature and they are warm White. I always set may camera AWB to tungsten (3000K) and I have no issues.

I just wondered may be a different temperature which can provide us to get better details or like that.

I digged the internet about lights, spectrum, wavelenths vs vs and it is so complicated :)
Even the power supply effects the characteristics of the light.

Then I realized that I am happy with my ikea leds :)
Regards.
Omer

Charles Krebs
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Post by Charles Krebs »

If you have not already seen it, check out this thread (and some or the links therein):
http://www.photomacrography.net/forum/v ... hp?t=32870

The "color temperature" or "CCT" of LEDs (or some other light sources such as fluorescent bulbs) is really a very rudimentary specification and does not provide much insight as to it's color rendering (CRI) and photographic usefulness since these light sources do not behave as a "black body radiators", which was the original basis for color temperature values. It is a starting place, but you need to know more about the spectral distribution

Black Body Radiation
Image

LEDs and fluorescent bulbs often have pronounced "peaks" and "valleys" in their spectral distribution. This is less than ideal, but in reality they can often be very adequate, as can be seen by the many great shots made with the simple Ikea lamps on this forum.

lonepal
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Location: Turkey

Post by lonepal »

Hi Charles;

I already checked the toppic that you adviced and learned lots of things about CRI and spectral distribution, very interesting.

I want to DIY a special lamp for my macro Works but there are a lot of choices about leds, I am excited.

I also cheked pre manufactured lamps or bulbs but good ones are very expensive and I do not trust Chinese seller WHO sells CREE leds on Ebay.

I realized that the characteristics of the light are a very important matter for photography.
Regards.
Omer

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