Best way to photograph both COOL and WARM white LED tints?

selfbuilt

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Hi all,

I'm working on updating my 4Sevens Mini reviews with data from the "warm tint" specimens (i.e. the lights that are currently up for pre-order). Note that these are true warm tints, not the "neutral tints" that most people commonly refer to as warm.

I'm struggling a bit with the best way to present them in my reviews. :thinking:

To help you understand the difference between the tints I am talking about, CPF user DFiorentino has complied an excellent set of tint bin graphs:
Cree Xlamp cool: http://img30.imageshack.us/i/creexlampcwfull.jpg/
Cree Xlamp neutral-warm: http://img170.imageshack.us/i/creexlampnwwfullix9.jpg/

Premium standard "cool white" tints are typically in the 5500-7000K range, while common "neutral white" tints are usually in the 4000-4500K range. In contrast, these new "warm white" tints are likely in the 3000-3500K range. This poses a significant problem for photographic comparisons. :sigh:

Why do I say that? Well, commonly we use our camera's automatic "sunlight" white balance for most beamshots (~5200K in the case of my Canon, which is about typical). While not a bad compromise, I know a lot of people have complained that this commonly puts the "neutral white" tints in a poor cast. It certainly makes the "warm tints" look pretty awful.

Here are some reference shots of colorful objects taken during the day in nautral light, and at night under regular household incadescent lights. Since the daylight shots were taken indoors near a window on an overcast day, I have used my camera's "overcast/cloudy" white balance (~6000K):

Day-overcast1.jpg

Incan-overcast1.jpg


Clearly, that second picture is not what the world looks like to most of us at night in our homes. :rolleyes: But if I present warm tint LEDs using a sunlight/overcast white balance, that's exactly what I am going to get. :green:

One solution that I see being suggested here is to use a camera's incandescent white balance (~3200K for my Canon, which is again typical). Unfortunately, all that does is create the opposite problem of grossly favoring the "warm tints" to the exclusion of all else.

Don't believe me? Here's the same setup again taken with my camera's "tungsten" white balance:

Day-tungsten1.jpg

Incan-tungsten1.jpg


Ok, that incandescent shot sure looks great - but is that top shot what you think the world looks like during the day outside? I don't think so ... :whistle:

The solution to this problem would seem to be to go with a compromise intermediate value. Unfortunately, this is non-trivial to ascertain - and my camera gives me limited options. There is also the problem of the magenta–green axis, which is not automatically compensated for.

To show you what I mean, here is an animated GIF of the daylight condition, followed by the Mini AA "cool white", Mini AA "warm white" and a Solarforce L2 P60 incandescent - all done under the common "sunlight" ~5200K white balance.

Mini-sunlight.gif


Although not ideal for "warm tints", it is certainly better than the extremes presented earlier. But note the slightly green "cool white" image, and the slightly pinkish P60 incan image? Frankly, I'm just not satisfied with sticking with the common sunlight white balance for these comparisons.

The best I've managed to come up with so far is my camera's fluorescent white balance (~4000K). Take a look:

Mini-fluorescent.gif


This is a not bad representation overall. But if I were to compare it to what my eye sees in each of these conditions, it seems to be erring slightly in favour of the warm tints.

At the end of the day, what best matches my eye for ALL conditions is something in-between the sunlight ~5200K and fluorescent ~4000K white balances. As a result, my plan is to present all beamshots under both those conditions with the recommendation that people expect the "truth" to be somewhere in-between.

What do you think of my plan? Does this match your experience? I'm not looking for an absolute solution here - just something that I think most people can easily grasp while being as fair as possible to all tints (and is not an insane amount of extra work for me :rolleyes:).

I think providing both ~5200K and ~4000K white balance photographs will do. I'm curious to hear your thoughts. :)
 

jcw122

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Your plan sounds like a good idea.

Also, shots of walls and outdoor objects might be useful too, instead of just indoor objects.
 

LED_astray

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I'd be interested in the results done with your assortment of colors and auto white balance. Our eyes (brains) compensate, the AWB is intended to mimic our vision, so maybe that would be the most representative of perceived color. (Of course it is like to screw up other aspects, maybe brightness, as part of the processing. And since it is processing you probably need an assortment, as you have, of colors in the image.)

Or maybe not, YMMV, etc. :)
 

somename

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Sounds like a good plan to me.

Any chance of side by side wall shots?

Can you include some outdoor shots of vegetation? I purchased the warm white mainly for outdoor use while camping and hiking, so I would be interested in some of those pictures.
 

selfbuilt

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Also, shots of walls and outdoor objects might be useful too, instead of just indoor objects.
Can you include some outdoor shots of vegetation? I purchased the warm white mainly for outdoor use while camping and hiking, so I would be interested in some of those pictures.
Those will be coming. :) I took a few with sunlight white balance the first night, but was not happy with the result (that's what got me going with the indoor test shots). Unfortunately it's rained every night since, and I'm going to be out of town for the next week - so it will have to wait until I get back.

Manual white balance?
Yeah, except my camera doesn't offer it (and it would likely only be an estimate at best). The problem is finding one balance that works for such a wide range - fundamentally not easy, because ...

I'd be interested in the results done with your assortment of colors and auto white balance. Our eyes (brains) compensate, the AWB is intended to mimic our vision, so maybe that would be the most representative of perceived color. (Of course it is like to screw up other aspects, maybe brightness, as part of the processing. And since it is processing you probably need an assortment, as you have, of colors in the image.)
... exactly, our brains compensate in real life.

BTW, that's also why I haven't specified exposure time in the shots above - I specifically let the camera choose auto-exposure adjustment. That way, I don't have to worry about about how subjective brightness difference bias the comparison (I just have to worry about the camera's auto-adjust ;)).

Oh, and I also used the Olight diffusers to even out the beam profiles (again, those hotspots are distracting).

Again, nothing is perfect, I'm just going for the least misleading! :)
 

GunnarGG

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I have very little experience doing beemshots but when I tried I couldn't find a whitebalance that showed both neutral and cool white in the way I saw it.
One possibel way to go is to shoot in RAW format and then you can set the white balance at any level you wish in your computer and then make the picture look exactly the way it looks in real life. This will result in different whitebalance for warm, neutral and cool.
It will then not be very scientific but just show your subjective view of the tint.
 

selfbuilt

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I have very little experience doing beemshots but when I tried I couldn't find a whitebalance that showed both neutral and cool white in the way I saw it.
One possibel way to go is to shoot in RAW format and then you can set the white balance at any level you wish in your computer and then make the picture look exactly the way it looks in real life. This will result in different whitebalance for warm, neutral and cool.
It will then not be very scientific but just show your subjective view of the tint.
Interesting idea, but my S5-IS doesn't have a RAW mode (well, not unless I go for one the hack firmwares ;)). Might be worth exploring for those with time on their hands ...
 

ToNIX

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GunnarGG

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I am way to slow typing, English making me even slower.

Yeah, except my camera doesn't offer it

Well, I guess RAW wasn't a very good idea then...
I will try some experimets myself somtime.

... exactly, our brains compensate in real life.

I work at a eye clinic and have several times met people that after cataract surgery comes home and discover that their red sofa actually was violet and the sky was blue like never before and so on. And some people get yellowtinted lenses at surgery and some get lenses without tint. There are several factors that matters how we experience tint I guess...
 

Yavox

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I would start with getting manual white balance - calibrated on a sheet of white paper in the middle of the day, in the shadow.

Then I would use some photo-editing software (like Photoshop or Gimp) with some plugin with white balance correction functionality. Even without the RAW format in the camera (just JPG) you should be able to make the whole image look cooler or warmer. I would take the pictures of cool, neutral and warm tint, transfer them to the computer, launch the photo editor and manually correct the white balance with the software, looking at the flashlight and at the screen comparing the results until I would believe I got the best match of what is on the screen with what I really see.

After all 3 pictures' tints are corrected manually, I would turn all 3 flashlights on at the same time and bring all 3 edited pictures to the screen (next to each other) to make sure that the relation between the pictures on the screen is close to what I see when looking at the flashlights' beams.

All of the above is of course not free from errors - there is no guarantee that other peoples' monitors render the colors exactly like yours and that what we will see is exactly what you have seen. But I believe that the result of such computer-aided beamshots correction will be much more similar to the reality than any other method.
 

Bass

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selfbuilt, you will need to do a custom white balance for each shot using a spectrally neutral reference (white balance card / grey card). That is the only way.

There is no point taking beamshots with a tungtsen WB setting set and I don't understand why more and more people here think you should :shrug:.

The standard of using a daylight (5600k or similar) white balance setting works fairly well - you can differentiate between tints consistently. You can see green in some XP-G tints, yellow in some XR-E and yellow/purple in Osram GD emmitters. Cool white will be rendered blueish and 'warm' with more of a yellow orange. Incandescent looks on beamshots, at 5600k, fairly accurately like it does in real life use IMO. It is not perfect but it is a consistant standard and is far more accurate than a tungtsen WB setting.

My opinion would be to stick with daylight for the group comparisons (they are legacy compatible with your older reviews that way) and do custom white balance settings for individual.

Sure, it is more work but with the regard your reviews, images and opinions are held and the amount of web traffic and Google importance you have, a camera with a raw function can be justified.
 

trailstoride

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My suggestion is to include a small white sheet in the photo, perhaps a 1 x 1 inch square of paper. Take your photo using the white balance you feel is closest to what you see - such as the sunlight ~5200K or fluorescent ~4000K white balance you mentioned.

Take a series of photos, starting with your "reference" lighting.

Then load the reference jpg image into a photo editing program (I use photoshop elements) and use the eyedropper to set the white balance according to the white paper square in the photo. This will correct the white balance, and give you the red and blue corrections. Jot these corrections down, and use these same corrections to set the balance of the remaining photos. You will end up with all images corrected to white balance of the "reference" lighting image.
 

Yavox

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My suggestion is to include a small white sheet in the photo, perhaps a 1 x 1 inch square of paper. Take your photo using the white balance you feel is closest to what you see - such as the sunlight ~5200K or fluorescent ~4000K white balance you mentioned.

+1

With a small white sheet of paper on each photo you will be able to find somebody to fix the white balance of each photo for you, if you decide for some reason to leave the photo editing to someone else.
 

Bass

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A white sheet of paper is ok but it should not really be used to set white balance. White paper will be bleached and likely contain optical brighteners. It will be very lucky if it is anywhere close to neutral.

You need a reference card or 'shoot through' lens disc to obtain correct white balance. Any card must be neutral - i.e reflect equal quantities of R,G,B light.

Sorry to keep banging on about this but if you are bothering to take the time and adding an additional step of setting a custom white balance, you might as well do it properly. Using white paper to do this is miss-information.
 

Yavox

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A white sheet of paper is ok but it should not really be used to set white balance. White paper will be bleached and likely contain optical brighteners. It will be very lucky if it is anywhere close to neutral.

You need a reference card or 'shoot through' lens disc to obtain correct white balance. Any card must be neutral - i.e reflect equal quantities of R,G,B light.

Sorry to keep banging on about this but if you are bothering to take the time and adding an additional step of setting a custom white balance, you might as well do it properly. Using white paper to do this is miss-information.

How does the reference card look like and where to get it from?
 

GunnarGG

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I have taken some pictures that I tried to post but I don't know how.
I tried the "Insert image" button but only get a line to type an URL. Shouldn't I be able to browse my computer there also? In the FAQ it says there should be a 'Manage Attachments' button but I can't find it. :shrug:
 

selfbuilt

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Hmmm, interesting discussion guys.

My S5-IS does of course have a custom white balance mode, but I couldn't easily think of what I would set it on that would work for everything without re-doing the white balance for each shot (back to the original problem). The idea of the photo-gray reference card, RAW shooting modes, and manual white balance setting sounds the best - but I can tell you right now that I don't plan to upgrade my camera for the sake of depicting a couple of warm tinted lights. :rolleyes:

And I don't like the idea of manually adjusting each image on the monitor to match what I see (almost endless problem of monitor settings, room lighting, decreased bit depth due to post WB-set JPGs being mucked with in paint shop, aargh).

I'll have to give this more thought ...

I have taken some pictures that I tried to post but I don't know how.
I tried the "Insert image" button but only get a line to type an URL. Shouldn't I be able to browse my computer there also? In the FAQ it says there should be a 'Manage Attachments' button but I can't find it. :shrug:
The images have to already be stored on a web served somewhere - you can only link to the URL here in the forum.
 

Yavox

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Did you think about making a short movie, not the pictures? Some time ago I had a problem with mailing some pictures showing the color of my wooden window casing and the wall bricks - whenever I tried to take a photo, the color was always slightly different from what I have seen. The tint was important, because we had to choose proper wood, that would match the color of the wall. The problem got solved unexpectedly when I tried to make a short movie (with the same camera and the same white balance settings as the pictures that were bad) - when making a moviem the colors somehow got recorded much better. I have sent a few pictures made from single movie frames and they were really OK. This is probably because of the way the CMOS (CCD?) matrix works in a camera - I cannot explain the effect but maybe this technique would be worth trying...
 
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