My new toy - a colour meter.

[SteveF]

An interesting thread - as someone who sometimes seeks to reproduce correctly colours through to printing stage.

Has a colour meter helped identify those light sources which appear similar to others, but which in fact produce specific spectral lines which look "white" but which induce colour shifts in the interaction with dyes and other colour forming chemicals?

The bane of mixed light sources has always been with us since colour photography, (and maybe even before) with replacing household light bulbs with "daylight filtered" ones, or putting blue filter inside lampshades to "correct" lighting. Fluorescent lighting where the phosphors can give very uneven colour light being a common problem, especially for reds and browns.

Yes. The colour meter has given me a full spectrum of each light source and the means to input the numbers to result in correct shades, whites and blacks. On this meter one can read a light source in about 5 secs, note that and move on to the next light source, meter, note and so on. You don't need to input immediately into the camera and if you do shoot raw then you can take those readings back to base and input them directly into your PP.

To give an example of my testing and the results I'm getting; I read one flourescent light at 3150kelvin with a colour correction index of B5,A2.5. Then moved onto another and read 3550kelvin and correction index of B5,A2. This shows me most flourescents seem to need the same colour correction but the kelvin values change and they age, quality etc. Now that's put information into my head that a white/grey card doesn't so I'm learning as I'm going along. To capture the full 'wave' of some cycling lights with a grey/white card has troubled me in the past but the meter captures all this data and shows it on a graph.

There's a colour correction setting on my G1X and G16 too. So I can apply the correction without taking the meter with me as I learn what colour shift is likely to be. It's still early days and I do tend to take longer absorbing information nowadays but I guess it's a sign of age

[SteveF]

Oh, and another thing I've noticed; the presets of Tungsten (3200), Flourescent (3800) etc in Canons are way out. Tungsten on our UK currents of 240 volt are commonly 2900 I've found. Flourescent is 3200 to 3500 on average and the horrible latest energy savers can be as low as 2300 (yuk!). To get below 2500 tho I have to go to 'custom' WB or, yeah ok, shoot raw.

No wonder my eyes are going ... I need to get out more.

[xpatUSA]

Yes. The colour meter has given me a full spectrum of each light source and the means to input the numbers to result in correct shades, whites and blacks. On this meter one can read a light source in about 5 secs, note that and move on to the next light source, meter, note and so on. You don't need to input immediately into the camera and if you do shoot raw then you can take those readings back to base and input them directly into your PP.

To give an example of my testing and the results I'm getting; I read one flourescent light at 3150kelvin with a colour correction index of B5,A2.5. Then moved onto another and read 3550kelvin and correction index of B5,A2. This shows me most flourescents seem to need the same colour correction but the kelvin values change and they age, quality etc. Now that's put information into my head that a white/grey card doesn't so I'm learning as I'm going along. To capture the full 'wave' of some cycling lights with a grey/white card has troubled me in the past but the meter captures all this data and shows it on a graph.

There's a colour correction setting on my G1X and G16 too. So I can apply the correction without taking the meter with me as I learn what colour shift is likely to be. It's still early days and I do tend to take longer absorbing information nowadays but I guess it's a sign of age

I'm curious as to how exactly we can "input [those numbers] directly into your PP"? It seems, from what has been said, that a light source gets characterized by a color temperature and what looks to me like Munsell color codes (hue, chroma). The illuminance from each source at the subject (and hence the lighting balance) wasn't mentioned, unless I've misunderstood something.

Not knocking the method, which obviously works for you - I'm just interesting in the nuts and bolts of it, having never used a spectrometer myself.

[edit]I've just had a look here and have learned a little a bit about the Sekonic.[/edit]

Price made my eyes water though

[PhotomanJohn]

With this Spectromaster it shows the B/A and G/M box and where to place your pointer in the camera in 'white balance correction' in the menu of most dSLRs. It shows in one case B5/M2 so I moved the pointer to five clicks towards Blue and 2 clicks down towards Magenta and used the kelvin readout to set my camera manually to that kelvin reading.

Steve - You have gotten me quite interested in this subject. I have skimmed through the C-700 manual and it is very impressive.

I am a bit confused about your statement above. I am a Nikon shooter and with my cameras the white balance correction screen is used to modify a standard white balance like sunlight, shade and the rest. According to the camera manual, that correction screen is not used when one is setting a specific K temperature. In the K setting screen one sets the "B/A value" by setting the K temperature and then sets the G/M value.

So I assume if I used one of these meters I would ignore the target color temp setting and just input the measured temp and the G/M value. I also assume that even if I am creating RAW files, when I open them in ACR and select the "As Shot" white balance setting I will be taking advantage of the settings I made using the color meter.

Except for the steep entry price, this seems like a simpler method than creating a custom white balance, shooting the Color Checker, creating a DNG file then the profile and then applying the profile in ACR. Or does the Color Checker process provide a higher degree of color correction?

John

P.S. Thinking about it a little more, the Color Checker method also corrects for color rendering errors in the camera and the lens as Ted noted with his Sigma. I am not sure how significant these factors are. It truly is a closed loop correction.

[SteveF]

I'm curious as to how exactly we can "input [those numbers] directly into your PP"? It seems, from what has been said, that a light source gets characterized by a color temperature and what looks to me like Munsell color codes (hue, chroma). The illuminance from each source at the subject (and hence the lighting balance) wasn't mentioned, unless I've misunderstood something.

Not knocking the method, which obviously works for you - I'm just interesting in the nuts and bolts of it, having never used a spectrometer myself.

[edit]I've just had a look here and have learned a little a bit about the Sekonic.[/edit]

Price made my eyes water though

Hi Ted,

Ok, let me clarify my comments because I've drifted about a bit on latter posts.

Having taken say a meter reading under lets say tungsten, when shooting raw, keep a note of the kelvin value and the colour correction values. When opening the file in a raw converter input the kelvin figures instead of 'as shot' and input the colour correction values wherever they may be. Now as I don't have the experience of any raw converter except for Canon DPP or rawtherapee I really cannot explain but Canon DPP it's under 'fine tune' just below the white balance kelvin boxes.

So the fine tune sliders are B and A then M and G. Just put into this set of sliders the info from the colour correction screen which is accessed from the icon at the bottom of the meter. This then gives us two adjustments one of kelvin and the other of the balance.

When the meter button is pressed the meter will show on different pages accessed by the icons on the front screen exactly what you need according to what you are wanting to achieve. So, if you want tungsten to become daylight (in a scene of mixed lighting on set) you would put a target value into the meter first, then meter the light source, then it gives different values for different makes of filters to bring that to 5200k or whatever you want. This is for instance to match a tungsten daylight bulb to match the window light of daylight for instance. That's primarily for lighting gaffers.

Hope I haven't caused further confusion?

Yes, the price is absolutely eye-watering!

[SteveF]

Steve - You have gotten me quite interested in this subject. I have skimmed through the C-700 manual and it is very impressive.

I am a bit confused about your statement above. I am a Nikon shooter and with my cameras the white balance correction screen is used to modify a standard white balance like sunlight, shade and the rest. According to the camera manual, that correction screen is not used when one is setting a specific K temperature. In the K setting screen one sets the "B/A value" by setting the K temperature and then sets the G/M value.

So I assume if I used one of these meters I would ignore the target color temp setting and just input the measured temp and the G/M value. I also assume that even if I am creating RAW files, when I open them in ACR and select the "As Shot" white balance setting I will be taking advantage of the settings I made using the color meter.


John

John,

You do have this right.

However I'm not familiar with the colour checker method, DNG and ACR profiles only white/gray cards in custom white balance.

My purpose was to use this predominently under artificial light, not daylight unless attempting to gel lamps to daylight on set or stage. I haven't used this in daylight yet.

Hope this helps a bit!

[PhotomanJohn]

Thanks Steve

I made the a statement about ignoring the target temperature which was not correct. The target temperature is what you want to simulate by making the color corrections indicated on the meter.

John

[SteveF]

Steve - You have gotten me quite interested in this subject. I have skimmed through the C-700 manual and it is very impressive.

I am a bit confused about your statement above. I am a Nikon shooter and with my cameras the white balance correction screen is used to modify a standard white balance like sunlight, shade and the rest. According to the camera manual, that correction screen is not used when one is setting a specific K temperature. In the K setting screen one sets the "B/A value" by setting the K temperature and then sets the G/M value.

John,

I don't know which Nikon you have but in the D4 pdf download I see you can alter presets on page 157 and there's further info on page 169. I see what you mean in that the kelvin setting sets the B/A before you move to the G/M setting. I'm not sure of the workaround on this one I' afraid. Maybe a few Nikon shooters could chip in?

[SteveF]

Thanks Steve

I made the a statement about ignoring the target temperature which was not correct. The target temperature is what you want to simulate by making the color corrections indicated on the meter.

John

Hi John,

From the manual:

'If you are not using LB index/filter and CC index/filter values, you can omit this step' - that's the step setting the target value in the instructions page 61.

It is a truly comprehensive device and hey, it runs on two AAs instead of some silly and expensive CR or whatever type batts. It is possible too but, I haven't yet explored it to customise the views to get the values on one page instead of clicking to another. It also has a socket to plug into your computer to either download firmware/software updates or to upload from the meter memory to the computer all the graphs and settings from your days shoot.

Do I now sense you're looking for the 'click to buy' button now?

[jcuknz]

I often find the 'RAW' camp members quite insufferable as they advocate the 'true path' seeking 'perfect' colour .. which to me is some unknown 'quality' as I concentrate on the subject matter seeing that I was tested twice and found colour deficient though not blind ... but then fortunately I am not serving customers who all believe the colour that they see is correct ... I guess one of the advantages of having been a photographer in B&W days and rarely shooting colour until digital came on the scene

Many years ago I bought a colour temperature meter and having 'dun my dough' discovered to use it I would need a whole box-full of CC filters ...so it remained in my junk box for years ... so I am very happy to read about a modern version and its usefulness in digital ... thanks SteveF

[xpatUSA]

Hi Ted,

Ok, let me clarify my comments because I've drifted about a bit on latter posts.

Having taken say a meter reading under lets say tungsten, when shooting raw, keep a note of the kelvin value and the colour correction values.

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So the fine tune sliders are B and A then M and G. Just put into this set of sliders the info from the colour correction screen which is accessed from the icon at the bottom of the meter. This then gives us two adjustments one of kelvin and the other of the balance.

Aha! Now it is clear . . those sliders are Blue-Amber and Magenta-Green in a 4-axis color space similar to Lab. Nothing I have uses those exact sliders (unless I've missed them in RawTherapee). Curiously, my Panasonic camera has two sliders in the custom WB setting menu

Thanks and good luck with the new method.

[PhotomanJohn]

I'm not sure of the workaround on this one I' afraid.

Steve - A workaround is not needed because both settings are made on the Kelvin screen and the color correction screen is simply not used when in the Kelvin white balance mode.

John