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03/30/2006 03:08:44 PM · #26 |
Originally posted by Bear_Music:
Originally posted by GeneralE:
ISAAC ASIMOV: On sounding like an expert! |
He's my hero too, General! Describes the both of us to a T doesn't it? And I think we can add Kirbic to the know-it-all list also...
R. |
I knew I'd heard of this theory before ...
Since we cannot know all that there is to be known about anything, we ought to know a little about everything.
--Blaise Pascal (1623 - 1662) |
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03/30/2006 03:12:43 PM · #27 |
Originally posted by GeneralE:
I knew I'd heard of this theory before ...
Since we cannot know all that there is to be known about anything, we ought to know a little about everything.
--Blaise Pascal (1623 - 1662) |
It's the song of the Rennaisance Man!
Robt.
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03/30/2006 04:00:50 PM · #28 |
| Okay - I can understand the general principle that different light sources will cause colors to be wonky - so we have white balance settings and warming/cooling filters. But I don't understand what the complication is that we can't just adjust the "tint" slider? Why is the raw better to work with than a processed jpg? |
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03/30/2006 04:04:03 PM · #29 |
Probably because the color of the light doesn't shift all of the other colors equally.
For example, UC Berkeley's colors are blue and gold -- under yellow lights, their uniform would photograph black and white. |
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03/30/2006 04:12:07 PM · #30 |
Originally posted by GeneralE:
Probably because the color of the light doesn't shift all of the other colors equally.
For example, UC Berkeley's colors are blue and gold -- under yellow lights, their uniform would photograph black and white. |
Well - wouldn't that be calculable? I mean, every pixel has an "apparent" color recorded by the camera from some part of a scene that had a "true" color. How the true color is recorded by the camera as an apparent color depends on the "temperature" of the light source. So it seems to me that knowing any two of those variable ought to let us derive the 3rd. What I don't understand is why that works better in raw vs jpg.
So maybe my real question is related to what kind of information is lost going from RAW to jpg - part of it I understand as the compression algorithm for jpg, but a jpg still will give you an apparent color for every pixel so I don't see why we can't just as easily change WB from a jpg as RAW. |
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03/30/2006 04:32:31 PM · #31 |
Originally posted by joebok:
Okay - I can understand the general principle that different light sources will cause colors to be wonky - so we have white balance settings and warming/cooling filters. But I don't understand what the complication is that we can't just adjust the "tint" slider? Why is the raw better to work with than a processed jpg? |
You can in fact make the same adjustments to a processed JPEG file. It's not quite the same thing as the "tint" slider though. The best way to make the adjustment is using curves. Set the black and white points in the "RGB" curve which acts on all channels, then, working on the individual channels, place a point in the center of the curve and pull either slightly down or up. To warm a photo, for instance:
- On RGB curve, set the black and white points
- On Red curve, place a point in the center and drag slightly upwards
- Adjust blue curve similarly downward
- Tweak green curve to balance it to taste
- Refine above as desired
- Finally, back in the RGB curve, adjust contrast by placing two points at the lower and upper third and creating a slight "s" to raise contrast (raise upper third point, lower the lower one) or do the opposite to decrease contrast.
All of the above can be done on an adjustment layer, so you can go back and tweak it later to heart's desire without incurring the greater image degradation that results from making multiple, "destructive" adjustments.
It's still much easier, and better, to do most or all of this in RAW conversion. All RAW converters I'm fimiliar with have Kelvin sliders that make warming and cooling a one-touch change, and most also offer more detailed adjustments as well. My goal in RAW conversion is to get the exposure, black and white points, color balance, contrast, and saturation all as close as possible to my final intent as possible. In this way, changes to the image after conversion are minimmized, and smoother tonality is preserved. Remember that a RAW file essentially stores the number of photons that have arrived at each site; it's not really even an image yet because no bayer interpolation has been applied. There are typically 12-bits/channel of data depth available, from which you will normally create an 8-bit/channel output file. Your goal should be to use that 8 bits to it's fullest and not to make strong adjustments after converting, since doing so will inevitably degrade the image somewhat.
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03/30/2006 04:40:24 PM · #32 |
Originally posted by joebok:
So maybe my real question is related to what kind of information is lost going from RAW to jpg - part of it I understand as the compression algorithm for jpg, but a jpg still will give you an apparent color for every pixel so I don't see why we can't just as easily change WB from a jpg as RAW. |
Other than the said compression. Going from RAW to Jpeg, you lose 4 or more bits of data detail. Jpeg is 8-bit, many RAW files are 12-bit. Doesn't seem like much, but that extra information gives you extra color depth to work with in color shifting.
The biggest disadvantage to shifting color in JPEG though is that each shift of color starts emphasizing ISO noise. Even low noise images start looking noisy if you start shifting the colors too much.
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03/30/2006 05:13:47 PM · #33 |
Originally posted by fotomann_forever:
The biggest disadvantage to shifting color in JPEG though is that each shift of color starts emphasizing ISO noise. Even low noise images start looking noisy if you start shifting the colors too much. |
Like this ... : )
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03/30/2006 06:49:35 PM · #34 |
Originally posted by kirbic:
...
My goal in RAW conversion is to get the exposure, black and white points, color balance, contrast, and saturation all as close as possible to my final intent as possible. In this way, changes to the image after conversion are minimmized, and smoother tonality is preserved. Remember that a RAW file essentially stores the number of photons that have arrived at each site; it's not really even an image yet because no bayer interpolation has been applied. There are typically 12-bits/channel of data depth available, from which you will normally create an 8-bit/channel output file. Your goal should be to use that 8 bits to it's fullest and not to make strong adjustments after converting, since doing so will inevitably degrade the image somewhat. |
Many thanks - I think this brought me a few steps forward in understanding! |
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12/02/2006 02:26:53 PM · #35 |
| same problem I took some picture a bedroom and furniture this morning and set up the white balance in tungsten but the picture on the lcd looks blue to me so what do I do. is this normal? how do i fix it to make it look natural |
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12/02/2006 04:27:28 PM · #36 |
I like shooting tungsten outdoors, particularly at night/ twilight.
It can make for electric blue skies.
This is a somewhat extreme example of that:
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12/02/2006 05:28:00 PM · #37 |
One of the things I miss about my old OLY was that it would let you set the WB off of just about any color. If I set wanted to set it off of something orange it would do it, then I could save it. It didn't matter what color it was it would do it. I used to carry different paint sample cards in my bag so that I could see what different wb settings would do...here are a couple fun ones I did one night shooting a sunset that wasn't as fantastic as I hoped. These were saved in my camera under house lights then used at sunset.
and
My evolt won't. I've tried and if it can't find white it just gives an error for you to redo. Wonder if it is just a problem with it or a new design...pretty much sucks.
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12/02/2006 05:38:12 PM · #38 |
Originally posted by sabphoto:
My evolt won't. I've tried and if it can't find white it just gives an error for you to redo. Wonder if it is just a problem with it or a new design...pretty much sucks. |
It might depend on the mode you are in -- see if you have a "custom" setting which will let you set the WB to a non-white color. |
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12/02/2006 05:56:48 PM · #39 |
Originally posted by GeneralE:
Originally posted by sabphoto:
My evolt won't. I've tried and if it can't find white it just gives an error for you to redo. Wonder if it is just a problem with it or a new design...pretty much sucks. |
It might depend on the mode you are in -- see if you have a "custom" setting which will let you set the WB to a non-white color. |
I hadn't tried other modes, thanks I'll give it a shot. In normal P mode, if the color I'm setting my white balance off of is close to white (say grey or tan) it will set ok, but anything too far off will just give an error. |
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12/02/2006 06:21:14 PM · #40 |
Or you can shoot in RAW and then dicker with your WB to your heart's content in the RAW processor; highly recommended.
R. |
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12/02/2006 07:51:10 PM · #41 |
With my Fuji S3, I sometimes create a custom white balance thru a filter that's opposite to the color that I want. By shooting a white card with flash to set a custom balance in the camera while using a slightly cooling glass filter, sunsets can be photographed looking warmer with no glass filter to cause extra reflections in the lens. Just a thought. I know that the colors can be adjusted in post processing, but this saves time if you know you will get the desired effect in camera.
Now here's a new problem. If I use that method to create a warped custom white balance, and then use that white balance to shoot a photo for a "basic editing" challenge, will it be DQ'd for the advance camera tinkering before the capture?
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12/02/2006 07:57:08 PM · #42 |
hey, always wondered this, is adding test IN YOUR CAMERA legal?
I would think so, because it says no text allowed "during editing" in the rules. |
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12/02/2006 10:49:50 PM · #43 |
Originally posted by Bear_Music:
Or you can shoot in RAW and then dicker with your WB to your heart's content in the RAW processor; highly recommended.
R. |
I still tend to set the white balance for what I want to achieve, even though I shoot in RAW.
Seeing the preview images with the appropriate colour casts helps me compose for whatever I'm trying to achieve, while shooting. In some cases I'll compose differently based on the feel, so getting that mood right helps while shooting.
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12/06/2006 09:07:09 AM · #44 |
| Speaking of white balance, I have a kelvin setting on my camera. I can adjust the kelvins from 1000 up to 9999. What does this have to do with setting a white balance? I am sure it has to do with color temperature, but I am not sure how to use this. It has a slider on the right,as well, which allows me to adjust the degrees of kelvin, I think. anyway, does anybody know about what this might be used for, and if it has a purpose under certain lighting conditions? |
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12/06/2006 10:54:20 AM · #45 |
Originally posted by Gordon:
Originally posted by Bear_Music:
Or you can shoot in RAW and then dicker with your WB to your heart's content in the RAW processor; highly recommended.
R. |
I still tend to set the white balance for what I want to achieve, even though I shoot in RAW.
Seeing the preview images with the appropriate colour casts helps me compose for whatever I'm trying to achieve, while shooting. In some cases I'll compose differently based on the feel, so getting that mood right helps while shooting. |
Oh, sure: it's just good practice for a lot of reasons to set WB properly, no question. I certainly try to, including setting tungsten WB for twilight shots if I want the blue cast. It's just that RAW allows you to mess with it after the fact if you didn't get it quite right or want to experiment with some radically different.
R. |
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12/06/2006 11:04:33 AM · #46 |
Originally posted by ladymonarda:
Speaking of white balance, I have a kelvin setting on my camera. I can adjust the kelvins from 1000 up to 9999. What does this have to do with setting a white balance? I am sure it has to do with color temperature, but I am not sure how to use this. It has a slider on the right,as well, which allows me to adjust the degrees of kelvin, I think. anyway, does anybody know about what this might be used for, and if it has a purpose under certain lighting conditions? |
Degrees Kelvin is the standard measurement of the "color temperature" of light. A higher number is "cooler" (more blue) than a lower number, Daylight on a cloudless day at noon is roughly 5500 degrees Kelvin, tungsten lighting from incandescent bulbs is roughly 3200 degree Kelvin, Daylight in open shade (more of the light comes from bounced blue-sky illumination) is roughly 7000 degrees Kelvin, and so forth.
Using the Kelvin scale to preset your WB is something that is mostly handy when you are working with controlled lighting and a "color temperature meter" which actually measures the degrees Kelvin of the light falling on the subject. This is particularly important when shooting film, and even more so when shooting movies on film...
When working from RAW, you can use the degrees Kelvin WB adjustment to do some extremely subtle fine-tuning of the final color of the image if you wish; the "standard" WB settings are all approximations and do not take into account, for example, the different quality of daylight you get at different altitudes and different times of the year.
So if you find, shooting at your ski resort in midwinter, that you are consistently adjusting your WB in RAW upwards from, say, 5000K to 6500K, then by all means set custom WB in the camera to 6500K when shooting in those conditions. But if you don't have a color temperature meter, you're only going to be able to determine these settings by trial and error one way or the other, be it in camera or in RAW processing, and you're going to have to take notes.
Robt. |
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12/06/2006 11:27:30 AM · #47 |
actually there is no such thing as a "degree Kelvin." the term is just kelvin or kelvins, as in
0 kelvins = -273.15 degrees Celcius = Absolute Zero
ps -- sorry. AP chemistry flashback coming to haunt me.
Message edited by author 2006-12-06 11:30:32. |
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12/06/2006 11:27:36 AM · #48 |
Great thread, all.
I shot my last Free Study in ********* using the AWB. It was a quick shoot and I tellya I couldn't get it quite right in PP, even when converting from RAW. I fought the color tint all through PP and never did get it right.
So this leads me to another question. Woudn't using a gray card be the correct way to set WB? I have a gray card somewhere at home but I'm not really sure how to use during shooting - gray side and white side for mid and white point? How do I set those then when converting RAW, or do they get set next after RAW conversion?
Thanks!
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12/06/2006 11:35:45 AM · #49 |
Originally posted by muckpond:
actually there is no such thing as a "degree Kelvin." the term is just kelvin or kelvins, as in
0 kelvins = -273.15 degrees Celcius = Absolute Zero
ps -- sorry. AP chemistry flashback coming to haunt me. |
and the reason why, if it isn't TMI
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12/06/2006 03:27:02 PM · #50 |
Originally posted by mad_brewer:
Great thread, all.
I shot my last Free Study in ********* using the AWB. It was a quick shoot and I tellya I couldn't get it quite right in PP, even when converting from RAW. I fought the color tint all through PP and never did get it right.
So this leads me to another question. Woudn't using a gray card be the correct way to set WB? I have a gray card somewhere at home but I'm not really sure how to use during shooting - gray side and white side for mid and white point? How do I set those then when converting RAW, or do they get set next after RAW conversion?
Thanks! |
I've never set a custom WB from a card with digital. I know the principle of it, of course, but I use the WB adjustment in RAW instead. I'm not sure how/why it should be any more difficult to get it right in RAW (speaking of fine-tuning) than to do a custom WB; I mean, all the options are there in RAW, what more is needed? But if I WERE setting a custom WB in the camera, I'd be inclined to use a white card and fill the frame with it.
The problem of WB setting, though, usually comes from mixed light sources, and custom WB off a card is not going to help much there since typically with mixed light sources different parts of the scene hare illuminated by different colors of light, and the card (of course) can only be in one place at a time.
The "professional" way to deal with it, if it's that important to you, is to get a color temperature meter and use that. In mixed lighting you can take readings at various places in the scene, and then average those out to derive a custom Kelvin and program that in, I suppose.
It's not really an area I've explored in digital, but it was a MAJOR concern when I was working as an architectural photographer, where we had to do color temperature readings on interior shots then build a custom filter pack of various colored gels to correct the light in front of the lens. This is basically the same thing as custom WB, of course.
Robt. |
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