Processing frustration (or numerical values in PS/LR?)

divamum

For the most part, I do my processing by "eyeball". I do what looks good to my eye, check it on a couple of monitors, soft-proof it it's going to be printed via SM and hope for the best. So far, so good - no real problems.

But I'm currently "deep processing" some headshots and going NUTS with it. They're quite good SOOC shots, I was happy with my "rough edits" that I did for proofs, and now the more I work on them the more I'm just not happy no matter what I do. If I bump up the contrast on one (calibrated) monitor, then I'm not happy with it on another one. If I soften it, it looks wishy-washy. On one monitor everything looks blown out.

SO... any tips, particularly more empirical ways of checking for hotspots and plugged-up shadows by the numbers? This is an area of processing which has defied me to date, so please treat me like a total PS n00b in this regard, despite the fact I've been using PS and LR for a while with (mostly) satisfactory results.

Thanks heaps - I'm getting insanely frustrated, and really need to figure out how to NAIL the processing since these are for clients instead of myself or "just friends". The bar has been raised....

I've just upgraded to LR3 and also use CS3 and calibrate my monitors using a Huey.

Thanks!

Dan7312

I don't claim any expertise in color, but emprically this is what I have been doing in LR. In the develop panel I type J to make the blown out pixels red and the 0 pixels blue.

I set the white balance.

If there are red pixels I adjust the exposure down until they just go away. If there are no red pixels I adjust the exposure up until just before they appear.

If there are blue pixels I adjust the black level down until the just go away, or up until the just appear.

Then I do other adjustments.

Take this with a grain of salt, this is just what I've been doing to try to understand how color works.

BTW, LR always works in Pro Photo color space, but when you export you images it converts to the color space you chose, usually sRGB. Pro Photo is bigger than sRGB but it squeezes in the colors as need, called perceptural intent, meaning as best it can to make things fit but not changes things too much as far as the human eye is concerned.

My 2 cents...

BinaryFx

Dan, just to be clear, the internal colour working space of ACR/Lr is not exactly ProPhoto (the colour is, the tone is not), as it uses a linear gamma of 1 (while ProPhoto is gamma encoded with a 1.8 tone response curve).

So I personally prefer to think of this as the ACR or Lightroom colour working space and to try not to mention ProPhoto so as not to confuse the single unalterable internal working space with one of the user selectable hard-wired rendering/output spaces (such as ProPhoto RGB, Adobe RGB, sRGB etc).


Stephen Marsh

http://members.ozemail.com.au/~binaryfx/
http://prepression.blogspot.com/

BinaryFx

divamum wrote: »

SO... any tips, particularly more empirical ways of checking for hotspots and plugged-up shadows by the numbers? This is an area of processing which has defied me to date, so please treat me like a total PS n00b in this regard, despite the fact I've been using PS and LR for a while with (mostly) satisfactory results.

The basics for an info noob? Run your cursor around the image and look at the values displayed in the info palette/panel/area.

In Photoshop RGB, pure blown out white is 255r255g255b - while pure plugged black is 0r0g0b. Equal values are neutral (r=g=b), so 128r128g128b is a gray tone, however it is not 50% in most gamma encoded RGB working spaces. A value of 255r0g0b would be pure red.

You will have to study output using a "step wedge" to evaluate what the min/max RGB values that hold detail are for your particular printing method. Perhaps something like 235-245rgb for neutral highlights and 10-20rgb for shadows.

EDIT - in addition to my action linked above, more step wedge links here if needed:
http://www.google.com.au/search?q=photoshop+step+wedge

Photoshop can also display the numbers in the file in other colour modes - some find HSB or Lab to be more human friendly, while old prepress guys like myself breath CMYK.

I suspect that you will do more of your work in Lightroom, so you may prefer to spend the time learning how to do things there. Lightroom does not use the 0-255rgb range, it uses percentages for the numerical readout, unlike ACR, Lightroom info values are internal or "abstract" and are not tied to an output space (% are more human friendly than linear gamma 16bpc RGB readings).

You would have to learn how the Lightroom % readings relate to the files when they are exported to a gamma encoded working space such as sRGB and how these files print/output.


Stephen Marsh

http://members.ozemail.com.au/~binaryfx/
http://prepression.blogspot.com/

Dan7312

Hmmm, the LR documentation says the internal color space is ProPhoto. They don't mention gamma setting, or at least I couldn't find that.

"Adobe Lightroom uses the ProPhoto RGB colour space internally and will always embed a profile for this colour space within images that are exported via the Edit in Adobe Photoshop command"

BinaryFx wrote: »

Dan, just to be clear, the internal colour working space of ACR/Lr is not exactly ProPhoto (the colour is, the tone is not), as it uses a linear gamma of 1 (while ProPhoto is gamma encoded with a 1.8 tone response curve).

So I personally prefer to think of this as the ACR or Lightroom colour working space and to try not to mention ProPhoto so as not to confuse the single unalterable internal working space with one of the user selectable hard-wired rendering/output spaces (such as ProPhoto RGB, Adobe RGB, sRGB etc).


Stephen Marsh

http://members.ozemail.com.au/~binaryfx/
http://prepression.blogspot.com/

BinaryFx

Dan7312 wrote: »

Hmmm, the LR documentation says the internal color space is ProPhoto. They don't mention gamma setting, or at least I couldn't find that.

"Adobe Lightroom uses the ProPhoto RGB colour space internally and will always embed a profile for this colour space within images that are exported via the Edit in Adobe Photoshop command"

Dan, I presume that Adobe mean that the default export/rendering space uses ProPhoto RGB unless one selects say sRGB or Adobe RGB - which would probably map "cleaner" to the internal working space that is based on ProPhoto RGB chromaticity using a 1.00 gamma. End users can't select or change this internal working RGB, it is transparent to the user.

As Adobe have changed the gamma from 1.8 to linear 1.0 - the profile is no longer strictly ProPhoto RGB, however it is based upon this profile.

Camera sensors and raw camera data are linear:

http://www.adobe.com/digitalimag/pdfs/linear_gamma.pdf
http://www.adobe.com/products/photoshop/pdfs/understanding_digitalrawcapture.pdf


Clear as mud?

A link:

http://www.digitalphotopro.com/software/image-processing/photoshop-lightroom-part-2.html?start=1

A quote:

Quote from Jeff Schewe:
"Admittedly, since Lightroom uses an unusual color space internally (ProPhoto RGB Chromaticities and a linear gamma for processing, but an sRGB gamma tone curve for histogram display), there are no traditional color readouts to be had. Insiders call the Lightroom color space Melissa RGB, named for one of the Lightroom team members."

Back when Lighroom 1 was released, there was a podcast from the developers that also mentioned this. I'll see if I can track it down...

http://photoshopnews.com/2006/03/15/new-adobe-lightroom-podcasts/


Stephen Marsh

http://members.ozemail.com.au/~binaryfx/
http://prepression.blogspot.com/

Dan7312

Thanks for the pointers, I sure they will help!

BinaryFx wrote: »

Clear as mud?

divamum

Wow - LOTS of information here overnight! Thank you all, and especially Stephen for your "Idiot's guide to the info panel" - that is EXACTLY the kind of stuff I need to get to grips with (and thanks for keeing it simple! My brain tends to glaze over the moment numbers are involved, so Simple Is Good until I get this stuff lodged in my brain with some degree of fluency! )

Keep it coming, folks

ETA: What working space SHOULD I have for LR? I have noticed that my shots look fine in LR, but a bit "flat" when exported and viewed through picasa or on the web.......

Dan7312

Here is an interesting podcast on color spaces and histograms in LR3

http://blogs.adobe.com/jnack/2006/07/lightroom_podcast_8.html

BinaryFx

divamum wrote: »

Wow - LOTS of information here overnight! Thank you all, and especially Stephen for your "Idiot's guide to the info panel" - that is EXACTLY the kind of stuff I need to get to grips with (and thanks for keeing it simple! My brain tends to glaze over the moment numbers are involved, so Simple Is Good until I get this stuff lodged in my brain with some degree of fluency! )

Perhaps take a moment to review additive colour theory and how RGB mode works/behaves...

Neutrals in RGB are easy, it is when it comes to evaluating colour that things get harder!

As my background is prepress, I find CMYK % "natural". Even when viewing an RGB image, I can set the info palette to display CMYK or any other colour mode, without changing the file from RGB. I find Lab mode readings to be very useful too and HSB mode has use for many folk as well when viewing the info palette.

Using the colour palette in Photoshop, you can experiment by dragging the sliders to mix different colours in different colour modes, which may also help you to learn how to evaluate via numbers (it will help you to learn how to mix colour via numbes).

However as you use Lightroom, you may have to learn to live with using RGB based % value readings which are not found in Photoshop.

ETA: What working space SHOULD I have for LR? I have noticed that my shots look fine in LR, but a bit "flat" when exported and viewed through picasa or on the web.......

It is not a "working space" as such, one has no control with this choice as one does in Photoshop with the RGB Working Space. It is what space you are exporting/rendering/editing once the file leaves Lightroom that is important.

If you are sending to a website or a non colour managed application or service - then something similar to your monitor is a good choice...which is usually sRGB.

If you are printing on a home inkjet printer, then you may wish to export out to Adobe RGB or ProPhoto RGB and then "convert to profile" to the printer profile (either in the printer driver or directly to the file).

The common mistake is to view or send a wider gamut space such as Adobe RGB or ProPhoto RGB to a narrow gamut device such as your monitor or a consumer level photo print lab. This is why one has to convert from one profile to the other (not assign).


Hope this makes sense,

Stephen Marsh

http://members.ozemail.com.au/~binaryfx/
http://prepression.blogspot.com/

arodney

Dan7312 wrote: »

Hmmm, the LR documentation says the internal color space is ProPhoto. They don't mention gamma setting, or at least I couldn't find that.

The internal processing space is indeed using a 1.0 “gamma” TRC but the histogram and percentage values use a 2.2 gamma curve like sRGB.
http://www.ppmag.com/reviews/200701_rodneycm.pdf

As long as you encode in ProPhoto, not a big difference at all in the supplied LR histogram and what you get in Photoshop. The gamma differences only slightly affect the vertical distribution AND any saturation clipping if present will be maintained in both representations. If however you use something far from ProPhoto primaries, something like sRGB, the final histogram you get in Photoshop can be pretty far off (they don’t look the same, clipping can be in effect).

Tone should be pretty darn close however. If you clip in the LR histogram, you’ll clip no matter what space you render.

BradfordBenn

Great stuff. I am struggling/examining the same question after my last prints did not look as expected (yes, SmugMug backed them and helped me correct them at no charge). I have been reading and rereading stuff trying to get it all straight in my head and this is helping quite a bit. I have a hunch nothing will beat some experience but now I don't think I am guessing as much.

BinaryFx

divamum wrote: »

If I bump up the contrast on one (calibrated) monitor, then I'm not happy with it on another one. If I soften it, it looks wishy-washy. On one monitor everything looks blown out.

Let's go back to the beginning...

What is the end product, monitor or print? You will have no control over how others setup their monitors and their viewing conditions, so I would not get too hung up on monitor differences.

I hope or suspect a print is the main concern. If a print, do you do the printing on your own equipment or is it sent to a lab or other print provider?

How consisent is the printing? If you print the same image a week/month or whatever later, how close is it to the first print? How repeatable is the process?

If the prints are consistent and repeatable, when you view the prints and then view the monitor softproof in Photoshop, how close do the two look to each other?

Can you be sure that your monitor is calibrated and profiled and being colour managed so that it will look close to the print? Can you be sure that what they print will be close to what your monitor is predicting?

Can you see where I am coming from with these questions?

You need to know that output is stable and consistent. You need to be able to see via softproofing what you will get when printing...otherwise you will be constantly chasing your tail.

EDIT: Additionally, if you have a known accurate "controlled print", then you can use this to verify that your current monitor calibration is "true".


Stephen Marsh

http://members.ozemail.com.au/~binaryfx/
http://prepression.blogspot.com/

divamum

All very important questions - this is very helpful indeed, Stephen.

BinaryFx wrote: »

Let's go back to the beginning...

What is the end product, monitor or print? You will have no control over how others setup their monitors and their viewing conditions, so I would not get too hung up on monitor differences.

Unfortunately, once they have left me I have no control how the shots are used but can be almost certain they will be both onscreen AND in varying kinds of print. I'm doing performer headshots, so it is likely that the digital files will be circulated for online use, 8x10's will be printed for audition submissions, and they will be used as promotional material which gets reproduced in programs and on flyers.

So I guess my goal is to process in a way which will provide the best compromises between those "end uses".

I hope or suspect a print is the main concern.

See above. I suppose I could start prepping and producing a master print instead of a master digital file. Have to think about that.

If a print, do you do the printing on your own equipment or is it sent to a lab or other print provider?

I have a low-end printer for my own use, but I'm not sure it's up to printing client shots (and I don't do enough of it at this point to justify investing in a good, pro printer). For prints I usually recommend they order through SM where I at least can proof (including soft-proofing - which I do as a matter of course anyway) the shots again.

How consisent is the printing? If you print the same image a week/month or whatever later, how close is it to the first print? How repeatable is the process?

Not something I've tried - see above.

If the prints are consistent and repeatable, when you view the prints and then view the monitor softproof in Photoshop, how close do the two look to each other?

Now this is something I need to do, if only to get a better sense of how SM is printing my stuff.

Can you be sure that your monitor is calibrated and profiled and being colour managed so that it will look close to the print? Can you be sure that what they print will be close to what your monitor is predicting?

Additionally, if you have a known accurate "controlled print", then you can use this to verify that your current monitor calibration is "true".

See above - I really need to get some kind of "calibration print" so that I have a better idea how to adjust my screen output. This is so obvious, and yet until this discussion hadn't occurred to me. Any suggestions for what to use as "control print"? Is there some kind of "test card" shot that's generally used, or is it better to use a shot of my own?

You need to know that output is stable and consistent. You need to be able to see via softproofing what you will get when printing...otherwise you will be constantly chasing your tail.

That sound you hear is me going round in circles....

Dan7312

SmugMug has calibration prints you can order...

http://www.smugmug.com/help/display-color

divamum wrote: »

See above - I really need to get some kind of "calibration print" so that I have a better idea how to adjust my screen output.

pathfinder

I'm surprised you haven't added one of these to your toolbag, divamum - http://photofocus.com/2009/11/24/x-rite-color-checker-passport-mini-review/

This will help resolve many of the questions you are asking.

Include a couple frames with the Passport in each session, each time the light changes. If your monitor is truly calibrated ( and with a Huey, that may be a potential issue ) your images should be very easy to color balance, perfectly. Your prints from Smugmug should match nicely.

divamum

oooooooo... Jim, nice link - that looks really interesting. Thanks!

That said, matching colour isn't usually my problem (Huey's done just fine on that score) - it's contrast/brightness, which is where I get frustrated (and why I reckon it's time to come to terms with some numbers).

I'll be ordering those calibration prints from SM too - I KNEW I'd seen something like that and just couldn't remember where (and couldn't find it when I searched). Tx for that link, too!

pathfinder

Specifically, look at the grey step wedge rendering in your calibration print for brightness and contrast. You want a full range of grey (neutral) steps from white to black, centered evenly around the middle grey tone.

divamum

pathfinder wrote: »

Specifically, look at the grey step wedge rendering in your calibration print for brightness and contrast. You want a full range of grey (neutral) steps from white to black, centered evenly around the middle grey tone.

Thanks - I'll definitely be looking out for one of those passports (althougH I have to say I think $100 is pretty pricey for the product, even including software). Before that, however, a calibration print. Then, presuamably, I prepare it as though I were printing, even if I'm not? Is that the best compromise position to adopt given the wide range of circumstances in which the photos could appear?

pathfinder

A standard color checker costs $69 bucks, so you get the case, the software, a grey scale etc for just $30 bucks more. http://www.bhphotovideo.com/c/search?Ntt=Color+checker&N=0&InitialSearch=yes

With care it should be good for years.

BinaryFx

divamum wrote: »

Before that, however, a calibration print. Then, presuamably, I prepare it as though I were printing, even if I'm not? Is that the best compromise position to adopt given the wide range of circumstances in which the photos could appear?

Yes, don't edit the calibration print, always keep the original.

You should have both the hard copy print and the file, you need both.

If the print is known to be accurate, then you can use that as a reference to ensure that your current monitor calibration, profiling and colour management is correct. This may have to be done using the Photoshop softproofing "proof setup" option.

With a "certified" print, the vendor measures known colour and tonal patches in the print and compares the readings to the file that created the print and provides a report with the image file and print. Without a certification/report, one hopes that they have good process control and that the print provided is at least visually compared to a known master control image.


Stephen Marsh

http://members.ozemail.com.au/~binaryfx/
http://prepression.blogspot.com/

NeilL

dm, it seems to me that Color Passport does no more than what carefully using a grey card and cwb does, for accurate colour.

As for optimal and consistent tonal range and contrast, nothing beats a light metre! I'd spend on a Sekonic L358 before an expensive wb tool. It's going to increase the potential of portrait work many, many times over.

I would suggest, assuming you are going to be shooting raw, you dial all the in-camera image adjustment menu items eg saturation, contrast etc, down to minimum. It won't affect the raw image (it will make the lcd view awful!), but the point is to get your camera histogram to show you maximum tonal range, for a more accurate guide to exposure, especially any clipping.

I would choose a raw converter which allows you to work from go in ProPhotoRGB, and to export in that. I wouldn't use ACR or LR for raw conversion. You can export into LR if you want to develop in there, or go directly into PS. In PS you can softproof in sRGB, or whatever. Always keep an unedited 16bit ProPhotoRGB tiff copy of your file in your archive. When you convert from ProPhotoRGB into say sRGB jpg, check the histogram, or use Gamut Warning, to check clipping.

Don't get hung on what you see on monitors. They show very low resolution, and the internet is only sRGB, and largely not colour managed. Work with your printing professional to get the best result from your file, if prints are what you are offering-selling.

Best.

Neil

arodney

NeilL wrote: »

dm, it seems to me that Color Passport does no more than what carefully using a grey card and cwb does, for accurate colour.

Considering it allows one to produce DNG profiles, I don’t see how you can say that. If you are referring to using a Passport just to gray balance a JPEG, well that’s probably not true either (is that gray card, whatever product you refer to spectrally neutral)?

I would suggest, assuming you are going to be shooting raw, you dial all the in-camera image adjustment menu items eg saturation, contrast etc, down to minimum. It won't affect the raw image (it will make the lcd view awful!), but the point is to get your camera histogram to show you maximum tonal range, for a more accurate guide to exposure, especially any clipping.

Agreed (somewhat). The LCD is a JPEG rendered from the raw data, using the in-camera processing. Your suggestion will make the LCD rendering somewhat closer to some, undefined, raw rending setting (possibly) in some as yet undefined raw processor. The Histogram and clipping is still science fiction in terms of what the raw data (a linear capture) provides. See: http://www.digitalphotopro.com/technique/camera-technique/exposing-for-raw.html

I would choose a raw converter which allows you to work from go in ProPhotoRGB, and to export in that. I wouldn't use ACR or LR for raw conversion.

The underlying processing color space in those products IS ProPhoto RGB primaries, it does allow one to render and encode in ProPhoto RGB so the comment is confusing.

Don't get hung on what you see on monitors. They show very low resolution, and the internet is only sRGB, and largely not colour managed. Work with your printing professional to get the best result from your file, if prints are what you are offering-selling.

The internet is color managed if you properly tag images and use a color managed browser. So saying the internet is only sRGB isn’t really accurate. Since so many users don’t use color managed browsers, we have to encode data for the web that is in the lowest common denominator, that’s sRGB. However, any user with a non color managed browser, and worse, without a calibrated and profiled display will still view an sRGB document differently from others. So sRGB is the least, worst color space for the web but the web isn’t sRGB centric, its “whatever your display color space sends to the display” centric outside ICC aware browsers of which there are only two. IOW, if you use Safari or FireFox, upload sRGB with tags, avoid Flash that isn’t ICC aware (older versions), profile your display, the sRGB image you see and the sRGB image others see with the same requirements will match (as they currently do in other ICC aware apps like Photoshop). IOW, do get hung up with what you see on the display when properly color managing images.

divamum

NeilL wrote: »

Work with your printing professional to get the best result from your file, if prints are what you are offering-selling.

Best.

Neil

Wow - glad to see this thread still active!

As I said elsewhere, one of my challenges is that I'm offering "print-ready" files which also have to be useable as web images. Once they leave me, I have absolutely no control over how they will be used - they may go into programs, brochures, be used on posters, turned into 8x10 headshot prints etc etc. Hence why I'm trying to develop a paradigm for myself. I think my best bet is to go with a SM calibration print and use that as a reference while editing on my own monitor - I can't edit for EVERY printer out there, but at least that way I can be sure that I'm appropriate for at least one, and therefore (hopefully) in the ballpark for others. It's a start, at least.

pathfinder

NeilL wrote: »

dm, it seems to me that Color Passport does no more than what carefully using a grey card and cwb does, for accurate colour.

As for optimal and consistent tonal range and contrast, nothing beats a light metre! I'd spend on a Sekonic L358 before an expensive wb tool. It's going to increase the potential of portrait work many, many times over.


Neil

The Color Passport is a highly corrected grey card, among other things, and allows you to warm or cool your image slightly and consistently as well. It also include a full color checker set of tones to be sure your color is consistent and accurate. And it comes in a nice, hard, plastic protective case.

I do agree, Neil, that proper exposure is really very important for good accurate color, and that the Sekonic L-358 is a great incident light meter. I rarely use mine outside of a studio, since I usually use my histogram and the Sunny 15 rule for my exposures out of doors. Indoors, in a studio, my L-358 rocks, especially for setting flash settings.

NeilL

I said *careful* use of a *grey* card, and that is what I mean, and that costs next to nothing. And it will get you *accurate* colour. If you want to *manipulate* your colour you can use editing software of whatever breed including Passport. Batch processing using a colour formula is standard in most applications. I don't see anything special about Passport which justifies the price and the marketing earnestness of this product.

dm's original post was in the context of studio portraits, and that is what I am addressing. Other types of photography, other techniques. In my opinion, the supreme tool for studio portraits is a light metre. My L385 can do reflective metering, also.

It's my view that using raw converters where defaults are transparent to the user is undesirable, and this is the case with ACR and LR.

I continue to maintain that the resolution and colour rendering capacity of monitors make them useful only as guides to the potential of files for printing, and that printing is a whole other area of technology and expertise, and that photographers who are selling must work directly with their printing professional.

I don't see how it's possible to get any information about your exposure while you are shooting, in raw, unless you are shooting tethered, without a in-camera histogram. Of course you have to be aware of the limitations of that histogram, but it is a very useful guide. That was my point - that you can increase the usefulness of the in-camera histogram, when shooting raw, in the way that I described.

Neil

arodney

NeilL wrote: »

And it will get you *accurate* colour.

What does that mean? Define accurate color. Before doing so, you might want to read this:
http://www.color.org/ICC_white_paper_20_Digital_photography_color_management_basics.pdf

dm's original post was in the context of studio portraits, and that is what I am addressing. Other types of photography, other techniques. In my opinion, the supreme tool for studio portraits is a light metre. My L385 can do reflective metering, also.

A light meter can be useful for exposure (and I’ll add, for JPEG and film, not necessarily for raw without understanding how exposure for raw and exposure for JPEG differ*). It doesn’t do squat in terms of color.

It's my view that using raw converters where defaults are transparent to the user is undesirable, and this is the case with ACR and LR.

What defaults, who’s? The two products allow one to build any kind of default setting. And if you mean the default setting from the manufacturer, who’s recommending one set that and leave all the other sliders alone?

I continue to maintain that the resolution and colour rendering capacity of monitors make them useful only as guides to the potential of files for printing, and that printing is a whole other area of technology and expertise, and that photographers who are selling must work directly with their printing professional.

I would not disagree that a display is a different output device than a print. To get that print, its darn useful to have a display who’s gamut, calibration, profile and soft proof aids in getting that print with as few prints as necessary. But no one here is saying a print is anything close to a prefect representation of a print. That would break the law of physics (one is an emissive device, the other a reflective item).

I don't see how it's possible to get any information about your exposure while you are shooting, in raw, unless you are shooting tethered, without a in camera histogram.

I think you mean a histogram of the raw data as rendered with the current settings shown to you by the converter. Of that I totally agree.

Of course you have to be aware of the limitations of that histogram, but it is a very useful guide.

Depends if your aim is to shoot the raw data to get the best raw data, or shooting it based on a JPEG*.
*http://www.digitalphotopro.com/technique/camera-technique/exposing-for-raw.html

NeilL

A light metre gives "readings" of physical data using an artificially constructed scale and units. These readings have only a correlational relationship with how the same data are processed by photographic and electronic equipment. There is no cause and effect relationship between a light metre and your image. However, the correlation is valid and reliable, and therefor useful. That's as far as it goes, and that's far enough.

No, I did not say a light metre is to be used principally for accurate colour.

Neil

arodney

NeilL wrote: »

A light metre gives "readings" of physical data using an artificially constructed scale and units. These readings have only a correlational relationship with how the same data are processed by photographic and electronic equipment. There is no cause and effect relationship between a light metre and your image. However, the correlation is valid and reliable, and therefor useful. That's as far as it goes, and that's far enough.

No, I did not say a light metre is to be used principally for accurate colour.

Agreed, and upon reading your post again (

As for optimal and consistent tonal range and contrast, nothing beats a light metre!)

, you indeed did not, my apologies.

colourbox

divamum wrote: »

Thanks - I'll definitely be looking out for one of those passports (althougH I have to say I think $100 is pretty pricey for the product, even including software)

pathfinder wrote: »

A standard color checker costs $69 bucks, so you get the case, the software, a grey scale etc for just $30 bucks more.

NeilL wrote: »

dm, it seems to me that Color Passport does no more than what carefully using a grey card and cwb does, for accurate colour.

I bought a Color Checker Passport and I think it's totally worth the extra $30. I already have a $69 color checker, but it's such a pain to take on a shoot because it's this big flat thing you somehow have to safely stow in the bag and you always think it's going to get bent or scratched or crushed.

In addition to having several useful color/grayscale charts versus just the one on the $69 version, the Passport comes as an hard shell plastic case that is designed to be able to stand up on its own horizontally or vertically if there is no model to hold it. The case is integrated so it's one piece; you never have to keep track of both a chart and its case. It's small enough that it's so much easier to have on you (I use small bags a lot). You never worry about whether it's going to get bent or folded, and since it closes up tight you are less concerned about light, atmospheric pollutants, or spilled coffee degrading the color squares. For an extra $30 you really do get a lot of benefit.

NeilL

No problems, Andrew. Thanks for the discussion. And a big personal thanks for the contribution you've made in your published writing to understanding and clarifying issues like these. I have found it very valuable.

Neil