Luminous Landscape Forum

Raw & Post Processing, Printing => Colour Management => Topic started by: Robert Boire on October 16, 2014, 11:09:30 pm

Title: ColorChecker Passport vs SpyderCheckr
Post by: Robert Boire on October 16, 2014, 11:09:30 pm
I am looking around at products that I can use to improve color accuracy and especially white balance, particularly for situations like night shots, night shots with street lighting..or even worse night shots with snow. I am considering ColorChecker Passport, SpyderCheckr + that nifty SyperCube and even ExpoDisk. Being able to take the solution out into the field is an important consideration.

Any thoughts? Recommendations?

Thanks
Title: Re: ColorChecker Passport vs SpyderCheckr
Post by: Bart_van_der_Wolf on October 17, 2014, 04:47:42 am
I am looking around at products that I can use to improve color accuracy and especially white balance, particularly for situations like night shots, night shots with street lighting..or even worse night shots with snow. I am considering ColorChecker Passport, SpyderCheckr + that nifty SyperCube and even ExpoDisk. Being able to take the solution out into the field is an important consideration.

Any thoughts? Recommendations?

Hi Robert,

Just a thought. What's wrong with using a daylight (or dual illuminant) calibrated profile, and using that at night? As a neutral reference for the local color balance you can then use something as physically rugged as a WhiBal (http://michaeltapesdesign.com/whibal.html).

The ColorChecker Passport will allow to make such an excellent output referred profile if you are using an Adobe centric workflow, which requires creation of DNG file based profiles. You can also use the camera's built-in daylight WB.

You then White balance on the test shot at night of the Whibal and shift the color temperature slider in your Rawconverter to whatever look pleases you.

Cheers,
Bart
Title: Re: ColorChecker Passport vs SpyderCheckr
Post by: deejjjaaaa on October 17, 2014, 10:19:58 am
I am looking around at products that I can use to improve color accuracy and especially white balance, particularly for situations like night shots, night shots with street lighting..or even worse night shots with snow. I am considering ColorChecker Passport, SpyderCheckr + that nifty SyperCube and even ExpoDisk. Being able to take the solution out into the field is an important consideration.

Any thoughts? Recommendations?

Thanks

you need to strart with saying which raw converter you are using -> it will define the tools that you can use to build profiles... if you have the light with spectrum very different from whatever sun delivers (with or w/o clouds, etc) then it might make sense to build such custom profile (otherwise just a proper WB and proper sensor saturation will do the work)...

for example if you are using ACR/LR and hence talking about .dcp profiles then SpyderCheckr OEM software does not build .dcp profiles - so unless you are a software developer capable to write your own code you are out of luck (OEM software for SpyderCheckr creates recipes, not profiles - unless something changed recently).
Title: Re: ColorChecker Passport vs SpyderCheckr
Post by: digitaldog on October 17, 2014, 11:19:54 am
Stick with the Passport for creating DNG profiles. And you only need to build a few.
Title: Re: ColorChecker Passport vs SpyderCheckr
Post by: Robert Boire on October 17, 2014, 04:52:31 pm
Thanks all. I think my particular issue is WB, though creating a calibrated profile can't hurt.


What's wrong with using a daylight (or dual illuminant) calibrated profile, and using that at night? As a neutral reference for the local color balance you can then use something as physically rugged as a WhiBal (http://michaeltapesdesign.com/whibal.html).


Well, nothing is wrong other than I did not think of it :).

Thanks I will look into the WhiBal.  Any comments on the ExpoDisk?  This seems so easy to use, especially for the field, that I wonder if I am missing something.

R
Title: Re: ColorChecker Passport vs SpyderCheckr
Post by: deejjjaaaa on October 17, 2014, 07:10:49 pm
Thanks all. I think my particular issue is WB, though creating a calibrated profile can't hurt.
how do you intend to create a "calibrated" profile in a uncalibrated profile creation workflow ( when tools used for dcp profiles do not allow you to enter measurements of your particular target  ;D , that is if you have tools /calibrated ?/ to measure it in the first place ) ... do you really think you are getting a "better" profile for a daylight ? no - you just getting a different profile (by removing some part of what Adobe thinks your colors shall be)... you can argue about taste, but not about "precision".


Thanks I will look into the WhiBal.  Any comments on the ExpoDisk?  This seems so easy to use, especially for the field, that I wonder if I am missing something.

http://rmimaging.com has some tests of WB targets (in terms how neutral they are, with a usual fine print about variations between items) - for example http://www.rmimaging.com/information/ColorChecker_Passport_Technical_Report.pdf has info about a dedicated WB target in xrite passport.
Title: Re: ColorChecker Passport vs SpyderCheckr
Post by: Bart_van_der_Wolf on October 18, 2014, 03:45:15 am
http://rmimaging.com has some tests of WB targets (in terms how neutral they are, with a usual fine print about variations between items) - for example http://www.rmimaging.com/information/ColorChecker_Passport_Technical_Report.pdf has info about a dedicated WB target in xrite passport.

FYI, I measured the spectral reflectance of my Whibal card, and of a BabelColor White reference, some time ago. The Whibal is pretty good:

(http://bvdwolf.home.xs4all.nl/temp/OPF/WB_RemissionSpectrum.png)

The Whibal is more than 2x brighter than a standard (18%) greycard, which helps in getting a lower (shot-)noise image to sample the White balance on. It also has a White and a Black patch to judge exposure levels.

Cheers,
Bart
Title: Re: ColorChecker Passport vs SpyderCheckr
Post by: deejjjaaaa on October 18, 2014, 11:16:53 am
and of a BabelColor White reference
which unfortunately ceased to be sold because of some patent dispute (???)
Title: Re: ColorChecker Passport vs SpyderCheckr
Post by: digitaldog on October 18, 2014, 11:43:43 am
which unfortunately ceased to be sold because of some patent dispute (???)
According to Danny, it was simply too expensive to produce and sell at that cost.
Title: Re: ColorChecker Passport vs SpyderCheckr
Post by: deejjjaaaa on October 18, 2014, 12:53:52 pm
According to Danny, it was simply too expensive to produce and sell at that cost.
he could simply cut Teflon sheets into smaller chips with a hole in a corner... done.
Title: Re: ColorChecker Passport vs SpyderCheckr
Post by: Robert Boire on October 18, 2014, 06:01:08 pm
how do you intend to create a "calibrated" profile in a uncalibrated profile creation workflow ( when tools used for dcp profiles do not allow you to enter measurements of your particular target  ;D , that is if you have tools /calibrated ?/ to measure it in the first place ) ... do you really think you are getting a "better" profile for a daylight ? no - you just getting a different profile (by removing some part of what Adobe thinks your colors shall be)... you can argue about taste, but not about "precision".

Ummm.... I read this several times and still cannot figure out what you are suggesting...

What I am suggesting is that I could use ColorChecker to create a dng profile.  However I still need something that allows be to easily set custom wb in the field. I am not sure gray cards are the most convenient thing to do this.
Title: Re: ColorChecker Passport vs SpyderCheckr
Post by: Bart_van_der_Wolf on October 19, 2014, 05:12:56 am
However I still need something that allows be to easily set custom wb in the field. I am not sure gray cards are the most convenient thing to do this.

Hi Robert,

Gray cards, especially spectrally neutral ones (not ones for determination of average scene brightness exposure) are the best for determining the actual WB at the spot they are used. One still needs to angle them correctly though, perpendicular to the optical axis, assuming they have a surface that has a somewhat Lambertian diffusion pattern.

The only drawback is that you cannot measure the WB at a long distance away with such a card (but then nothing can, not even the Expodisc), or at multiple spots at the same time. The card must be placed in the scene itself, although it can be done on a separate occasion, or at a location with similar lighting (no need to ask the lion to pose next to the graycard).

One typically wants to establish a known/neutral reference under a given illumination, and then adjust for color temperature to achieve a certain atmosphere. With lots of bright effect colors (e.g. neon light or gelled light) or colorful ambient reflection surfaces, one would not want to totally neutralize that, so the photographer still needs to think about what he/she is doing. This is no different than e.g. shooting with a blue sky, which will give blue shadows if we measure in the light and not in the shadows. Similar thing would be when shooting under a heavy tree leaf canopy, one can remove the green color cast but that would kill the atmosphere (although it would improve the color of e.g. human skin).

So in practice, one needs a neutral WB for colors that need to be exact, or only shifted a bit in color temperature, but it is possible to do that only locally where it matters and let local ambient colored reflections or light-sources do their thing elsewhere.

Cheers,
Bart
Title: Re: ColorChecker Passport vs SpyderCheckr
Post by: JRSmit on October 19, 2014, 10:30:40 am
Ummm.... I read this several times and still cannot figure out what you are suggesting...

What I am suggesting is that I could use ColorChecker to create a dng profile.  However I still need something that allows be to easily set custom wb in the field. I am not sure gray cards are the most convenient thing to do this.
CCP has a lightgrey card incorporated as well. So that can be used to eyedrop the color balance.
Title: Re: ColorChecker Passport vs SpyderCheckr
Post by: digitaldog on October 19, 2014, 03:34:43 pm
he could simply cut Teflon sheets into smaller chips with a hole in a corner... done.
So what he specifically wrote about the cost and price for consumers isn’t accurate or you have something solid about some patent dispute?
Title: Re: ColorChecker Passport vs SpyderCheckr
Post by: digitaldog on October 19, 2014, 03:35:24 pm
What I am suggesting is that I could use ColorChecker to create a dng profile.  However I still need something that allows be to easily set custom wb in the field.
Use the same Passport target.
Title: Re: ColorChecker Passport vs SpyderCheckr
Post by: Hening Bettermann on October 19, 2014, 05:11:52 pm
Hi Robert,

the built-in logic of the grey card method is to render the scene as if it was shot under standard light. If you want to white-balance the scene as you saw it, you need no cards. Here is how:
http://www.luminous-landscape.com/forum/index.php?topic=73620.0
further discussion here:
http://www.luminous-landscape.com/forum/index.php?action=printpage;topic=82738.0
post of october 04th, 2013

And if you are the lucky owner of a Sony a7(r), it's even easier and better: This camera allows you to set the WB in real time in live view - no need to make test shots; and you can adjust BOTH the yellow-blue AND the magenta-green balance!
Nobody seems to have praised Sony for this, so I will use the opportunity: BRAVO SONY! A great step forward towards a more true color rendition in landscape photography!

Good light - and true color! - Hening.
Title: Re: ColorChecker Passport vs SpyderCheckr
Post by: Tim Lookingbill on October 19, 2014, 05:49:59 pm
I'm actually starting to use the AWB influenced ACR/LR green/magenta Tint slider as an indicator of how much green is in the actual scene shooting indoors under fluorescent and landscapes at my local park at dusk which looks more green than I'ld thought.

If in ACR/LR I get a huge Tint of +20-30 toward magenta I know my eyesight wasn't playing tricks on my perception of the amount of green I was seeing. My workstation is close to these two shooting locations allowing the look of color temp to stay fresh in my mind.

It acts more of a training mechanism and AWB tester for post processing afterward when I view how magenta ACR/LR renders these shots. I no longer carry my WhiBal card because I know my camera's AWB and ACR/LR agree with each other on what R=G=B should look like which is what I don't want in most of my shots especially if wanting to preserve ambiance within the scene.

I can tell you snow looks gorgeous lit by direct sunlight using AWB on my Pentax K100D with Sony sensor and ACR/LR "As Shot" WB interpretation. It's when I start changing contrast and attempting to expand the DR of the image is when I have to resort to using the HSL panel especially on overly blue shadows.
Title: Re: ColorChecker Passport vs SpyderCheckr
Post by: Robert Boire on October 19, 2014, 09:05:16 pm
Use the same Passport target.

Yea, I got that. But is there anything wrong with the ExpoDisk as a WB target? Other than the additional cost?
Title: Re: ColorChecker Passport vs SpyderCheckr
Post by: Bart_van_der_Wolf on October 20, 2014, 02:49:48 am
Yea, I got that. But is there anything wrong with the ExpoDisk as a WB target? Other than the additional cost?

Hi Robert,

Suppose you want to take an image of a red tomato on a red backdrop. What would the Expodisc (which is intended to average the scene Luminance) see? How would an Expodisc (or similar) be of use to set the White balance in a way that Red stays red, but also potentially other colors as they should? All it would do is create a blurry red dominated impression of reflected subject colors, which will get color corrected by a shift to Cyan, in order to neutralize the color 'cast'.

The goal of a White balance tool is to get an impression of the spectral qualities of the illuminant(s) of the scene, the lightsource(s) and ambient reflections, that will determine how the subject color reflections will look.

Remember, illumination spectrum, minus subject spectral absorption, is reflected color spectrum. A spectrally neutral subject (e.g. a graycard) will allow to determine the illumination spectrum (an approximation due to the limitations of the tri-chromatic measurement and assumption of a continuous (blackbody like) spectrum), which is the input required for White balancing. We do not want to measure the subject colors, but we want to measure the illumination spectrum/color in order to approximate correct rendering of any color reflection.

Also remember that the scene illumination mostly comes from illumination sources that are behind the camera and to it's sides. Measuring (averaging color reflection) of what's in front of the camera only makes sense if it is of a subject with known spectrally neutral reflection (of that illumination behind the camera), or the same color as the illumination.

Cheers,
Bart
Title: Re: ColorChecker Passport vs SpyderCheckr
Post by: digitaldog on October 20, 2014, 10:14:14 am
But is there anything wrong with the ExpoDisk as a WB target?
It’s unnecessary. Use the Passport target for WB too!
Title: Re: ColorChecker Passport vs SpyderCheckr
Post by: brntoki on October 20, 2014, 10:43:44 am
Yea, I got that. But is there anything wrong with the ExpoDisk as a WB target? Other than the additional cost?

The ExpoDisk is supposed to be aimed at the light source, so if there is more than one light source the ExpoDisk will probably not be as accurate as a white balance card, assuming you can position the card in a way that it is reflecting those multiple sources (which may be really tricky often times). However, you can probably find some other way to do what the ExpoDisk is doing. For example, I found a cap to a bottle of salad dressing that was very similar to what you might find on a light meter for incident readings. I placed that over my lens and set the camera white balance using it. It was very, very good. I learned at that time, like has been pointed out, "perfect" white balance can kill the atmosphere. "Perfect" white balance is supposed to show you true color, while the colors we are seeing in everyday life are only "true" in a certain, ever-changing, context. Sometimes we need the "hard" truth, and sometimes the contextualized truth.
Title: Re: ColorChecker Passport vs SpyderCheckr
Post by: Bart_van_der_Wolf on October 20, 2014, 12:07:18 pm
The ExpoDisk is supposed to be aimed at the light source, so if there is more than one light source the ExpoDisk will probably not be as accurate as a white balance card, assuming you can position the card in a way that it is reflecting those multiple sources (which may be really tricky often times).

Aiming an Exposdic at the lightsource will miss whatever local ambient light reflection is also falling on the main subject surface, unless one walks up to the subject, turns one back to it and averages the incoming light. A graycard is much easier, and in case of the Whibal the best option if one also wants to be able and use it in rainy conditions or even under water or submerged in an aquarium tank. Also very easy to use with subjects that are covered by glass, if the card can be temporarily be put behind/under the glass.

Quote
However, you can probably find some other way to do what the ExpoDisk is doing. For example, I found a cap to a bottle of salad dressing that was very similar to what you might find on a light meter for incident readings. I placed that over my lens and set the camera white balance using it. It was very, very good.

As long as it doesn't yellow with age, and assuming it is spectrally neutral to begin with, that may work. I occasionally use a square piece Opaline glass that I also use for creating an LCC for flatfielding and color cast correction. The opal layer diffuses the transmitted light with microscopic bubbles, so it is pretty neutral and diffuse.

Quote
I learned at that time, like has been pointed out, "perfect" white balance can kill the atmosphere. "Perfect" white balance is supposed to show you true color, while the colors we are seeing in everyday life are only "true" in a certain, ever-changing, context. Sometimes we need the "hard" truth, and sometimes the contextualized truth.

Measuring white balance indeed is usually just a starting point, followed by a shift in color temperature, unless one does reproductions (which would require color balancing along the entire tonescale, or a specific profile).

Cheers,
Bart
Title: Re: ColorChecker Passport vs SpyderCheckr
Post by: rubencarmona on October 21, 2014, 10:15:14 am
Actually, if white balance is the only thing you need, a SpyderCube can be enough. It will last longer than a grey card, given that it's not out of carton but of pigmented synthetics. So even if you scratch it, the grey, black and white will stay neutral.

So the Spydercube is to correct the color temperature...

Tools like color checker and spydercheckr will calibrate the colors your camera interprets. So it will correct the color input of your camera to match the colors in real life. Thanks to the color patches as reference. Here both products do the same good work. It's just different methods. One is creating dng profiles, the other one is creating a preset to correct the colors in the raw metadata.
Title: Re: ColorChecker Passport vs SpyderCheckr
Post by: digitaldog on October 21, 2014, 10:50:45 am
Actually, if white balance is the only thing you need, a SpyderCube can be enough.
He needs a DNG camera profile!
Quote
So it will correct the color input of your camera to match the colors in real life.

Ah, no, not really.
Title: Re: ColorChecker Passport vs SpyderCheckr
Post by: Robert Boire on October 22, 2014, 08:46:34 pm

The goal of a White balance tool is to get an impression of ... ambient reflections, that will determine how the subject color reflections will look....

...Also remember that the scene illumination mostly comes from illumination sources that are behind the camera and to it's sides. Measuring (averaging color reflection) of what's in front of the camera only makes sense if it is of a subject with known spectrally neutral reflection (of that illumination behind the camera), or the same color as the illumination.


Well, I guess that depends on the nature of the scene and the illumination. As you and others have pointed out, putting a grey card in the scene may not always be convenient. I would think this is especially true when there is no definable object. Or to put it another way, when the whole scene is the object (ie no tomato to use your example), such as in a landscape.  The scene may have light sources in front and behind the camera and from the sides, for example street lights at night, which is my particular case. Pointing the ExpoDisk (or any of the other similar plethora of products) at the source would be a challenge. But then again, I would think it would be a challenge for a grey card as well. Or the scene may not have illumination coming from a particular direction, but may be generally amorphous such as on an overcast day.

I would think that if the goal is to get an `approximate` calibration of white balance for later post production that pointing the ExpoDisk at the scene would give reasonable, average results. The disk will be lit up from the reflected light from the various objects in the scene, much as a grey card may be lit up by reflections from the many objects.

Hey, either way I guess I will give it a shot. Its not that expensive. Or maybe I`ll just look for a suitable bottle of salad dressing :)

Cheers and thanks

Robert
Title: Re: ColorChecker Passport vs SpyderCheckr
Post by: Bart_van_der_Wolf on October 23, 2014, 02:43:14 am
I would think that if the goal is to get an `approximate` calibration of white balance for later post production that pointing the ExpoDisk at the scene would give reasonable, average results. The disk will be lit up from the reflected light from the various objects in the scene, much as a grey card may be lit up by reflections from the many objects.

Hi Robert,

Just using a predefined 'Daylight' white balance setting will produce a more predictable result, because it disregards any prominently colored objects in the scene that might skew the true WB determination. A gray card is different from a diffused scene measurement in that it is an object itself, with known 'color' and also intrinsically unaltered by surrounding mixed illumination, it just reflects the surrounding light and thus allows to separate the illumination from object colors.

If you want to base White balancing on an image of a diffused scene (which is all an Expodisc has to offer), you might as well use Auto WB on a defocused image of your scene and save some money ...

Cheers,
Bart
Title: Re: ColorChecker Passport vs SpyderCheckr
Post by: rubencarmona on October 31, 2014, 07:30:06 am
He needs a DNG camera profile!

Why?

Ah, no, not really.

What else?
Title: Re: ColorChecker Passport vs SpyderCheckr
Post by: Tim Lookingbill on October 31, 2014, 02:41:42 pm
Why?

What else?

Study the subject of color constancy as it relates to "pleasing" vs "accurate to real life" color imagery. Then you'll be able to use more words in your responses here.

Also find out why landscape/portrait painters going as far back as the Renaissance used a set number of specifically named paint colors to render photo realistic images that would allow them to maintain visually balanced color for long hours at the easel whether working under candlelight or window daylight.
Title: Re: ColorChecker Passport vs SpyderCheckr
Post by: rubencarmona on November 05, 2014, 09:48:32 am
I create camera-dedicated presets myself with the SpyderCheckr. But as he was most of all talking about white balance, I wanted to suggest him starting with a correct white balance. Probably that's enough for him, if not, of course he could go further...
Title: Re: ColorChecker Passport vs SpyderCheckr
Post by: Isaac on November 05, 2014, 12:14:05 pm
And if you are the lucky owner of a Sony a7(r), it's even easier and better: This camera allows you to set the WB in real time in live view - no need to make test shots; and you can adjust BOTH the yellow-blue AND the magenta-green balance!

As does the SLT-A35 (http://www.manualslib.com/manual/160055/Sony-Slt-A35.html?page=117) (although the range is not large enough to set UniWB); and as-you-say adjusting K G/M until the EVF is a visual match with the scene, can work as a kind-of what I saw when I was there hint. Of course, what you saw when you were there depends on whether you were looking at the sunlit scene for a couple of minutes and then looked into the shade ;-)

I'm more likely to set camera WB with a Digital Gray Card (http://store.rmimaging.com/digitalgraycard-100.aspx).
Title: Re: ColorChecker Passport vs SpyderCheckr
Post by: Hening Bettermann on November 05, 2014, 07:03:59 pm

> Of course, what you saw when you were there depends on whether you were looking at the sunlit scene for a couple of minutes and then looked into the shade ;-)

...at which time you can establish a second WB for the shadows...:-)
Title: Re: ColorChecker Passport vs SpyderCheckr
Post by: Robert Boire on November 06, 2014, 05:12:59 pm

I would think that if the goal is to get an `approximate` calibration of white balance for later post production that pointing the ExpoDisk at the scene would give reasonable, average results. The disk will be lit up from the reflected light from the various objects in the scene, much as a grey card may be lit up by reflections from the many objects.

Hey, either way I guess I will give it a shot. Its not that expensive. Or maybe I`ll just look for a suitable bottle of salad dressing :)

Well, so much for that idea. Tried it and it really sucks.  Brought it back. What I saw on the camera display screen  (yes I know its only an approximation) using AWB or Tungsten preset (they were virtually the same) was much closer to the scene than what I got with a preset based on the ExpoDisk, which gave completely garish results. For that matter I got decent results in LR using a strategically placed styrofoam cup as a reference.

Guess I get that grey card, though it would be cooler to do an in-camera correction.

R
Title: Re: ColorChecker Passport vs SpyderCheckr
Post by: Bart_van_der_Wolf on November 07, 2014, 04:10:51 am
Well, so much for that idea. Tried it and it really sucks.  Brought it back. What I saw on the camera display screen  (yes I know its only an approximation) using AWB or Tungsten preset (they were virtually the same) was much closer to the scene than what I got with a preset based on the ExpoDisk, which gave completely garish results.

Hi Robert,

Thanks for the feedback, it can help others. The outcome isn't all that surprising, but it never hurts to verify in practice.

AWB algorithms are usually much more clever than just averaging the reflected scene. They look for recognizable features/colors and use those to adjust the estimate. But nothing beats actually measuring the illumination itself (or the reflection of a known spectrally neutral subject), with the specific camera itself.

Quote
Guess I get that grey card, though it would be cooler to do an in-camera correction.

Do note that not all Gray/Grey cards are spectrally neutral (equal reflectance for all relevant wavelengths). They could also change over time, with use. That's why I like the WhiBal, easy to clean, weatherproof, very neutral, brighter than an exposure card (lower noise).

Cheers,
Bart
Title: Re: ColorChecker Passport vs SpyderCheckr
Post by: deejjjaaaa on November 07, 2014, 09:49:30 am
brighter than an exposure card (lower noise).
if you make a specific shot w/ WB target you can just expose it properly (spot meter and adjust), now if you want it to be in your regular shot along with the object it is another story - but then if it is somewhere along the border you might have other issues with colorshift for example.
Title: Re: ColorChecker Passport vs SpyderCheckr
Post by: Bart_van_der_Wolf on November 07, 2014, 10:10:10 am
if you make a specific shot w/ WB target you can just expose it properly (spot meter and adjust), now if you want it to be in your regular shot along with the object it is another story ...

And the latter is the normal situation, which is what I was referring to. For example with studio flash, the color temperature can change when the output power is changed. In addition, Adobe DNG profiles can exhibit a hue shift with altered exposure levels. That's when it helps to use a brighter WB target, because it will have lower noise with actual exposure levels, which allows more accurate WB sampling.

Quote
- but then if it is somewhere along the border you might have other issues with colorshift for example.

Call me an optimist, but a competent photographer is implicitly assumed ...

Cheers,
Bart
Title: Re: ColorChecker Passport vs SpyderCheckr
Post by: Robert Boire on November 18, 2014, 12:25:08 pm
Guess I get that grey card, though it would be cooler to do an in-camera correction.

Well that certainly worked out better, at least I am in the right ballpark. One thing I like about the WhiBal is that it is reasonably portable (fits in my back pocket) and looks more or less indestructible.

However even though the results are in the ball park..they are not quite right. Which probably leads to all sorts of questions about things I don't understand in WB in general.

In the test shots I did, the subject was sitting in artificial, indoor light (ie a living room) with bright blue clothing. The subject was holding the WhiBal. Uncorrected colors had a very yellow-orange cast as can be expected. After correction in LR using the WhiBal, the colors were slightly too cool (ie blue), particularly for the WhiBal  If anything I would have thought that if there was an overcompenstation it would have tended toward the warmer...ie remove the blue reflection on the WhiBal.  Incidentally I tried to correct using a white (but not clipped) surface in the image and got closer to where I should be (ie the correction was slightly warmer)

Or have I got all this reversed?

One thing I do not understand is LR recommends correction on a neutral gray object rather than a white object.

Thanks
Title: Re: ColorChecker Passport vs SpyderCheckr
Post by: deejjjaaaa on November 18, 2014, 12:48:39 pm
One thing I do not understand is LR recommends correction on a neutral gray object rather than a white object.
if they key word is neutral then it is obvious, if the key word is is gray may be to avoid the situation when you either clip "white object" /assuming that you might expose WB target along with something else and... might happen/ or (allegedly, with some cameras) expose it to the area near sensel(s) saturation where the situation with the sensel charge might get non linear (hence even a neutral object will be non neutral).
Title: Re: ColorChecker Passport vs SpyderCheckr
Post by: Tim Lookingbill on November 18, 2014, 04:15:51 pm
I believe as I understand from what I've read from Rags Gardner's explanation of sensor linearity that mid gray is more linear (accurate) over white which can be highly nonlinear as RGB channels go. Mid gray is just a safe zone for sensor non-linearity.

Very good explanation on sensor linearity from this site: http://rags-int-inc.com/

Click on "Technology" button on the left>click on "ETTR" button.