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eekellamFlag for United States of America

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How can I get a greyscale image (using Photoshop or any other tool) that is an accurate representation of a color image?

How can I get a greyscale image (using Photoshop or any other tool) that is an accurate representation of what I see when looking at a color image.  When I use the B&W, desaturate, or grayscale option in PS, I don't get anywhere near the values that I see; for example a yellow and a lavender where the yellow looks lighter when I squint at them are very different when I have PS convert to B&W or grayscale.  The yellow appears to be darker!

A digital camera photo with mode set to B&W of the screen shows the yellow to be lighter than the lavender by about the correct amount.

I assume that this has to do with the light energy reaction in the eye vs the value levels used in the RGB colors.  It seems that this function is useful enough to graphic artists that there should be a way to do this.
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qwerty021600
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Go to Image>> mode >> Grayscale in Photoshop serve your purpose ?
Technically, what you are calling 'incorrect value transitions' is not exactly right. How Photoshop converts your image to grayscale is based upon the way you have set up your color settings under Edit > Color Settings.
If you are not getting the results you are expecting it is because your Color Settings are not set up properly. If you set up your Color Settings properly, qwerty is absolutely correct.
Above comment should technically be an object I guess.
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To moderator:

Sorry - did not mean to step on any toes.

I thought that I had followed the rules.  I posted the second time before receiving any comment and explained how I arrived a workable solution (that was actually easier to use, more powerful and reversible).  I did not see the expert comment until after I posted my solution and withdrew the question.

I had tried Qwerty's response before asking the question and it sometimes yielded a grayscale conversion that was usable but took multiple steps and followed by undo action to get out of the resulting mode.  I'm not saying that Qwerty's response was unusable, just that I found a better way before I saw the response.

BTW Bong Soo's comment did not lead to an approach that changed the results much.  
I'm comfortable with PS for most of the graphics work that I need to do (I'm a traditional illustrator) but I'm not deeply knowledgeable of the intricacies of PS color.  Every reference book and tutorial that I find shies away from the subject saying - leave it to the professionals.  Okay; but if I need to become at least semi-professional in this area, where do I find the information?  I need to be able to dig into the subject of video and production color for research to teach a class that I am creating.
First, most likely, you didn't even give my comment a second glance. Saying that my comment did not lead to an approach that changed the results much means you didn't fully investigate it. Most likely didn't even investigate it. Color management is the heart of the issue - just because you don't understand it doesn't mean you should discount it. How you manage your color can DRASTICALLY affect the output.

Second, the reason you haven't been able to find the information you are looking for is exactly this: you don't want to spend your time down in the trenches learning it yourself. Guys like me who spent 15 years working with photoshop since its inception have, and we usually know our stuff. I will allow that I don't know everything but I know enough to identify the issue here - you obviously don't. It might behoove you to read what I wrote, again, and try to ask some intelligent questions.

Guys like you just want to come along and get some silver bullet short cut without doing any of the work. Oh well, good luck with that.
BongSoo - geez - maybe responding to questions form people who don't already know the answers isn't your bag.

I didn't mean to push your buttons.  I explained my status and the problem that I was trying to solve and acknowledged that I was looking for assistance not a recommendation to spend years of my life becoming expert in your field.

I did try converting to some other color settings with the result that one did produce a more usable value based representation, however, it required flattening the image and accepting warnings from PS when I opened files with other color profiles (I expected this as it is a natural problem - that's one reason I stick with a single profile and have chosen the one recommended by PS).

I suppose that I should have clarified my question with a few terms like "in a couple of steps" and "something that works like a filter" - the adjustment layer approach does just this with enough precision for my purposes.

I'm not expecting that I should have knowledge born of 15 years "down in the trenches" anymore than you should have my level of knowledge of real time telecom system design (my first 30 year career) or how to design and produce illustration art (my second career) but I would try to respond to questions about such with useful information and references.  I guess that's why I also enjoy teaching.

Once again - sorry about your blood pressure.
coolleomod:

Since there has been an objection filed against this question, I  guess I should go through some sort of drill to get it resolved and avoid being branded a trouble maker here.  I explained my action in a previous response but the question still seems to be open.  So how do I shut this thing down properly?  None of the options in the link you provided seem to fit exactly in that the answer from qwerty did produce a usable solution and the quality of the image was even more precise after playing with e color selections as suggested by BongSoo but the solution that I am using is the adjustment layer approach that I found on my own because it fits my need for a simple to use yet effective solution.  If the graceful way to do this is to award points to qwerty, I'll do that - I don't have to be right for the information to be useful - maybe qwerty will find my idea useful as well.
A valid workaround is not the best answer - this place is going down the tubes as is exemplified quite nicely in this series.
Okay - I see the insider eye poking - I'll let that slide by me.

I think that solutions need to be useful to the questioner even if not pedantically precise and demonstrative of comprehensive knowledge.  Since I was asking this question from my role as a journeyman artist and not a technologist needing to understand the in depth details of the color management system, an answer couched in functional terms was sufficient.  Both Querty and BongSoo were correct in what they had to say and collectively their answers addressed (without fully explaining; which was not needed)  why I did not get the results I expected with the grayscale change of mode.  My finding a solution that was simpler and more effective for the scope of my problem did not, in my mind reduce the range of their expertise.  In fact, BongSoo's explanation prompted me to realize that a better understanding of color management on my part would be worth the effort to pursue, that was why I asked for more indepth resources; I'm sorry that BongSoo saw such a request as an unintelligent question. BTW BongSoo, I have found and ordered a couple of books from Amazon that purport to provide a comprehensive overview of PS color management as their primary subject - thanks for the motivation.

So, how about we wrap this dialog up?  Is that something I do or someone else?  I realize that this may not be an intelligent question but I have pressing schedules at the moment and will have to dig into learning the whole EE etiquette in the near future.