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Author Topic: Camera Calibration??  (Read 3076 times)
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« on: September 28, 2012, 11:13:36 AM »
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I just stumbled into a new and somewhat confusing universe:  Camera Calibration!  I had never really looked at this before yesterday; I thought it was related to actual camera calibration (profiling).  Where you shoot a known target and generate a camera profile.  But such is not the case.... 

The settings may be camera related but they are different renderings of the image data.  Some are vastly different than the default: "Adobe Standard".  My question is which one is the most accurate rendering of what was shot?  I am adjusting some landscape images and the differences are startling.  Some settings eliminate a haze or color cast in the far distance that I did not even realize was there until I altered this setting.  I guess you can pick the one you like best, or go for accuracy?  Which is more "accurate": Adobe Standard or Camera Neutral?  Is it possible to say, or is it totally scene related? 

Thanks,

Paul

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digitaldog
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« Reply #1 on: September 28, 2012, 02:58:22 PM »
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It isn't about accuracy, it is about providing a rendering you like.
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Andrew Rodney
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« Reply #2 on: September 28, 2012, 09:34:08 PM »
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It isn't about accuracy, it is about providing a rendering you like.
and if somebody does a reproduction work ?
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digitaldog
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« Reply #3 on: September 28, 2012, 09:36:47 PM »
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and if somebody does a reproduction work ?

Then you hope for a visual match as much as possible. Much of that is subjective. Two numeric matches can result in a visual mismatch as we both know.
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Andrew Rodney
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« Reply #4 on: September 28, 2012, 11:13:33 PM »
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and if somebody does a reproduction work ?

If you are doing reproduction work and like for your colors to match the original, you choose the profile that gives you the colors that you like.
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deejjjaaaa
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« Reply #5 on: September 29, 2012, 12:52:59 AM »
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If you are doing reproduction work and like for your colors to match the original, you choose the profile that gives you the colors that you like.
you were going to say "you build", right ? because you need to build something before you choose something as there is nothing to choose from really...

we discussed recently how to expose the target and Eric Chan recommended (to get the highest quality profile) simply : 1) bracket 2) select the most exposed/ETTR'd target that still will be accepted by DNG PE - basically just trust some internal checks that Adobe put there...

now if we are building a profile for reproduction using some dcp profile building tools (DNG PE, Xrite or QPCard, may be I missed something), what shall we do ?

1) we shall not build any dual illuminant profiles for sure - we shall build a single illuminant profile for reproduction purposes, right ?

2) what about light - shall we use the light of the intended illumination (where the reproduction will be displayed - if we know that of course) ? shall we use some high quality standard light regardless ? 

3)  certainly such "reproduction" profile is just a part of the whole process, hence a question - are there any special considerations that must be taken (while preparing such profile) into account about further raw conversion (ACR/LR), possible postprocessing and printing ?

4) what are the checks that are possible (if possible at all) early in the process to understand if we are close to possible perfection (I mean as early as possible - not when we actually print a copy of the work being reproducted to compare visually or w/ some tools with the original) ?

I mean if that is a reproduction it shall not depend on what you like or not like... the shall be some dose of a formal approach.
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Bryan Conner
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« Reply #6 on: September 29, 2012, 12:57:00 AM »
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you were going to say "you build", right ? because you need to build something before you choose something as there is nothing to choose from really...

we discussed recently how to expose the target and Eric Chan recommended (to get the highest quality profile) simply : 1) bracket 2) select the most exposed/ETTR'd target that still will be accepted by DNG PE - basically just trust some internal checks that Adobe put there...

now if we are building a profile for reproduction using some dcp profile building tools (DNG PE, Xrite or QPCard, may be I missed something), what shall we do ?

1) we shall not build any dual illuminant profiles for sure - we shall build a single illuminant profile for reproduction purposes, right ?

2) what about light - shall we use the light of the intended illumination (where the reproduction will be displayed - if we know that of course) ? shall we use some high quality standard light regardless ? 

3)  certainly such "reproduction" profile is just a part of the whole process, hence a question - are there any special considerations that must be taken (while preparing such profile) into account about further raw conversion (ACR/LR), possible postprocessing and printing ?

4) what are the checks that are possible (if possible at all) early in the process to understand if we are close to possible perfection (I mean as early as possible - not when we actually print a copy of the work being reproducted to compare visually or w/ some tools with the original) ?

I mean if that is a reproduction it shall not depend on what you like or not like... the shall be some dose of a formal approach.

No, I did not mean to say build.  You need to choose the profile that you like.  Now, if you have to build a profile in order to like it, then so be it.  Build away.  And if you do not like a profile unless it is built to your exacting specifications, then so be it.  Build it...but, you have to choose it.  If you do not like the profile, you do not have to choose it...unless you want to...it is your choice.  It is not that difficult.  Suit yourself.  YMMV. etc.
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Rhossydd
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« Reply #7 on: September 29, 2012, 02:33:01 AM »
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I thought it was related to actual camera calibration (profiling).  Where you shoot a known target and generate a camera profile.  But such is not the case.... 
It can be the case.
There are several tools available that allow you build your own profiles using standard targets.

It's important to understand that many of the 'profiles' offered in Lightroom are there to simulate the in-camera picture styles that are available when shooting jpgs. Different cameras have different options depending on what the original maker offered, which accounts for the often significant differences seen between them.
Adobe then offer their own 'standard' profile which is often a good neutral default option.

Quote
Which is more "accurate": Adobe Standard or Camera Neutral?  Is it possible to say, or is it totally scene related?
It's best to avoid the "accurate" word here or you get into long pedantic arguments. ;-)
Building your own profiles for your specific camera (and shooting conditions) can be a useful aid to your workflow. You may be able to produce a profile that delivers a more pleasing rendition, and for specific conditions it may be 'accurate', but regarding it as scene related is the easiest way to think of them.
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Schewe
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« Reply #8 on: September 29, 2012, 02:39:10 AM »
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2) what about light - shall we use the light of the intended illumination (where the reproduction will be displayed - if we know that of course) ? shall we use some high quality standard light regardless ? 

Red herring alert...the light that you shoot under has zero to do with the light you look at a print under...are you intentionally making this harder that it needs to be (sure seems like you are trying to spread FUD rather than clearing thing up)...

Look, you create a DNG profile to render the raw capture as best as possible...then you use image processing to correct the image and soft proof the final output using the optimal ICC print profile–which if you know what you are doing, includes the spectral illumination of the final print viewing environment...there are numbers you can use if you need technical accuracy.

Why are you being so prone to disinformation and FUD doode...do you want to help people or are you simply trying to fluff up your own feathers?
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mac_paolo
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« Reply #9 on: September 29, 2012, 02:54:52 AM »
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Why are you being so prone to disinformation and FUD doode...do you want to help people or are you simply trying to fluff up your own feathers?
*
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Bryan Conner
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« Reply #10 on: September 29, 2012, 03:27:11 AM »
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Why are you being so prone to disinformation and FUD doode...do you want to help people or are you simply trying to fluff up your own feathers?
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Nigel Johnson
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« Reply #11 on: September 29, 2012, 04:30:27 AM »
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I just stumbled into a new and somewhat confusing universe:  Camera Calibration!  I had never really looked at this before yesterday; I thought it was related to actual camera calibration (profiling).  Where you shoot a known target and generate a camera profile.  But such is not the case.... 

Paul,

You appear to be confused and some of the other replies are rehashing detailed arguments arguments from other threads, I hope not to add to your confusion. You need to understand that Lightroom (LR) and Adobe Camera Raw (ACR) can use many types of 'profiles' for processing:

  • built-in camera colour profiles;
  • custom camera colour profiles;
  • internal colour profile (Mellisa RGB, the internal LR/ACR colour space; not discussed further);
  • International Colour Consortium (ICC) colour profiles (used for output to screen, file or printers and often called monitor or printer profiles; not discussed further);
  • lens distorsion profiles (not discussed further as they do not relate to your question).

You appear to be confusing the first two, which I will describe further. Adobe creates at least one camera profile for all supported cameras and this is called 'Adobe Standard'; there may be more than one version of this for older cameras as Adobe has sometimes provided  improved versions. 'Adobe Standard' is designed to provide a similar colour rendition from all cameras (which have different manufacturers' renderings); typically 'Adobe Standard' is more neutral than the camera manufacturers' defaults but is designed to provide pleasing rather than accurate colour. For many popular cameras Adobe also supplies camera matching profiles such as 'Camera Default', 'Camera Neutral', 'Landscape', 'Portrait', etc. These camera matching profiles are intended to provide a similar image to the JPEG files produced from the camera when the related in-camera setting is used. Note that the names vary with each camera and that they are specific to a given camera even if the same named profile is available for a different camera. They may well not entirely match the in-camera setting as they do not include image adaptive algorithms.

The second kind of camera profile is a custom profile that you create by photographing a test chart, usually a X-rite/Macbeth Colour Checker, using your own camera. The software used is usually the Adobe DNG Profile Editor (DPE) http://labs.adobe.com/wiki/index.php/DNG_Profiles or the X-rite Passport http://xritephoto.com/ph_product_overview.aspx?Action=support&ID=1257 software. An alternative target and software is also available from QPcard http://www.qpcard.com/. The profiles produced can be single or dual illuminant profiles and for accurate reproduction single illuminant profiles shot using the intended subject lighting are often used. Typically the camera profiles produced are more neutral than the 'Adobe Standard' profile. There are some indications that DPE may give more accurate colour than the Passport software (both can use the same calibration image) and that the QPcard may be better for accurate reproduction of artwork; however, there are conflicting views on the web and I have personally not carried out any testing.

You ask which is the most accurate profile. However, unless you are carrying out reprographic work or possibly needing to reproduce specific colours for commercial purposes, accurate colour may not be as important as pleasing colour. This has been discussed widely previously on this site and elsewhere and as this post is getting long I will not rehash the arguments. If you are not creating custom profiles it is best to check the available profiles; it is likely that either the 'Adobe Standard' or 'Camera Neutral' will be the most accurate but this may not be true as the rendering changes for different cameras. Custom camera profiles may be more accurate and DPE allows further editing of a profile (but this process is not easy).

Regards,
Nigel

P.S. As LR/ACR is a visual editing programme you need to use a monitor that has been calibrated using appropriate hardware. Using the monitor out-of-the-box or visual calibration methods will not give accurate results. Failure to use a calibrated monitor is likely to result in much greater deviation from colour accuracy than any camera profile choice.
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Keith Reeder
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« Reply #12 on: September 29, 2012, 07:50:04 AM »
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Why are you being so prone to disinformation and FUD doode...do you want to help people or are you simply trying to fluff up your own feathers?
Yeah, I'm going with that last thing...
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Keith Reeder
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« Reply #13 on: September 29, 2012, 09:42:56 AM »
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because you need to build something before you choose something as there is nothing to choose from really...

Confused by the text....

You the user certainly do not have to build anything if you don't want to or can't. Profiles (and it would be REAL useful to define what kind OF profile and for what purposes) are supplied by every raw converter I've looked at. And in Adobe land, you can edit them but maybe that is what you mean by build (and this is a totally optional step).
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Andrew Rodney
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« Reply #14 on: October 01, 2012, 08:56:26 AM »
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Thanks everyone for their replies!  Nigel, I am running a spectraview monitor.  My printer is not calibrated but I am getting good results with the canned profiles from Canson, and Epson 

Jeff, I guess your right when you say that accuracy is not paramount.  In the past, I have always tried to make my images look natural and close to what I remembered seeing at the time of capture.  Especially when I was working in Photoshop.  I have to say though, now that I am working in LR, I am straying further from the actual, and doing more enhancement.  My images are now much more interesting and "alive"....IMO

Thanks again,

Paul
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