B&W: differences between RGB desaturated and grey scale image

[robert blu]

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To convert my M10 DNG files I use the Silver Efex Pro extension via LR CC as starting point. After that I work the image with LR or sometimes PS CC to arrive where I desire.

 

From the interesting and instructive answer from Adan in this thread I learned the LR only desaturate the image which remains and RGB image, not converted to greyscale.

 

My final goal is to make inkjet print on my Epson P600 and also share the photos in the web.

 

What I do not know is  which  advantage there is in having the photo as pure B&W image in grey scale compared to have it as just desaturated RGB image as LR and SEP gives? It would only take an additional step in Photoshop to convert it in greyscale, not a big problem :-)

 

I made a small test and didn't notice any difference, but there is always something to learn...thanks in advance for your inputs.

 

robert

Edited November 6, 2017 by robert blu

[jaapv]

With a natively monochrome image, you will have a more precise tonal scale due to the lack of interpolation. 

The tradeoff is the ability to create (local) colour filter effects on RGB images as opposed to a richer tonal scale on monochrome files.

Greyscale images can be converted to RGB (three identical channels) to be able to add toning.

[adan]

Hi, Robert.

 

One reason I always keep my monochrome (desaturated) digital pictures in RGB mode is that once a picture is converted to true grayscale (one channel, gray values only), the whole "color management" system used by Photoshop and the Epson driver (printing software) falls apart.

 

In the Epson print dialogue box, the "Photoshop Manages Colors" selection switches to "Printer Manages Colors" and becomes grayed out (no longer selectable) and there is no longer an option to choose among the many profiles for different papers. One has to go deeper into the Epson settings to manually fiddle with Epson's own printer settings for media type.

 

And once I go back to printing color pictures, I have to reset that to "Photoshop Manages Colors," and then the software defaults to some silly profile (sRGB IEC61966-2.1) which has nothing to do with printing! - so I have to scroll through all the available paper profiles to find and select my own default again (Epson Premium Photo Paper Luster).

 

Every time.

 

Now - IF one is only printing B&W pictures, and/or wants to to use Epson's own proprietary "Advanced B&W" controls for tonality or color (sepia, etc.) or a proprietary setup like the Cone Piezography inks, then using grayscale images with that fixed workflow is fine.

 

But since I am constantly moving back and forth between color prints and "B&W" prints, I can't be messing around with swapping printer workflows every other image. And like you, I just have not seen a significant difference in the output, so I stick with the "RGB workflow" even when the image is B&W.

 

All my B&W print sales are made from desaturated RGB files. They are - literally - "fine prints!"

 

BTW - another of those "dirty little secrets" of inkjet printing - the Epson printers always uses all the color inks anyway (along with the gray and black inks), just carefully balanced to add up to gray. Regardless of whether the image is Grayscale or RGB. It makes for additional fine ink dots in light tones to avoid "speckly" near-white highlights, and otherwise render smooth and rich tonality. And of course, allows Epson to "tone" B&W images to sepia or some other color when desired.

 

(One can see this if a color print head becomes clogged when printing a B&W image - if it suddenly starts printing slightly blue, that means the yellow ink is not flowing correctly).

 

Even when I scan B&W film, I have Vuescan output the scan as a three-channel RGB .dng file (just like a Leica Monochrom .dng), simply so that it fits right in with my workflow (Vuescan automatically "equalizes" the R, G, and B values to make grays).

Edited November 6, 2017 by adan

[Jeff S]

Hi, Robert.

 

One reason I always keep my monochrome (desaturated) digital pictures in RGB mode is that once a picture is converted to true grayscale (one channel, gray values only), the whole "color management" system used by Photoshop and the Epson driver (printing software) falls apart.

 

In the Epson print dialogue box, the "Photoshop Manages Colors" selection switches to "Printer Manages Colors" and becomes grayed out (no longer selectable) and there is no longer an option to choose among the many profiles for different papers. One has to go deeper into the Epson settings to manually fiddle with Epson's own printer settings for media type.

 

And once I go back to printing color pictures, I have to reset that to "Photoshop Manages Colors," and then the software defaults to some silly profile (sRGB IEC61966-2.1) which has nothing to do with printing! - so I have to scroll through all the available paper profiles to find and select my own default again (Epson Premium Photo Paper Luster).

 

Every time.

 

...(snipped)....

 

 

I dealt with the same issues using the LR print module and Epson driver. But switching to ImagePrint 10 was a godsend.... custom profiles for virtually every paper and lighting condition, with color and greyscale, and no need to ever touch a color management or printer setting ever again. Just choose paper, profile, size and feed mechanism and IP makes sure every print setting is ideal.

 

IP is expensive (roughly same as my P800), but on the bright side, I would have had to spend twice as much on custom profiling gear to achieve similar results, and still having to deal with all the possible screw-ups resulting from the Apple/Adobe/Epson chain. I remember well when Apple messed up color management, without telling anyone.

 

Jeff

[robert blu]

Interesting, thanks for your answers. The amount of knowledge in the forum is really something special!

Grazie!

robert

[SilentShutter]

You create the file in RGB mode which means you have three chanels.

Reducing it to Greyscale would mean trow away 2/3 of the picture information !

Easy to understand why you shouldn´t do this right ?  

[robert blu]

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You create the file in RGB mode which means you have three chanels.

Reducing it to Greyscale would mean trow away 2/3 of the picture information !

Easy to understand why you shouldn´t do this right ?  

 

 

yes, easy. 

robert

[pop]

You create the file in RGB mode which means you have three chanels.

Reducing it to Greyscale would mean trow away 2/3 of the picture information !

Easy to understand why you shouldn´t do this right ?  

However, since all three channels contain the same information in a B/W image, you do not lose any information by discarding two of the three channels. You can easily reconstruct them by copies of the remaining channel, if you need three channels for any reason.

[jaapv]

Actually, you don't  throw anything away, as the three channels get combined-which makes no difference as they should be identical. Anyhow, as Photoshop and LR are based on LAB, I strongly suspect that the L channel is used.

There is no reason to convert to greyscale, however, unless you have managed to introduce an unwanted colour cast.

[Guest]

I dealt with the same issues using the LR print module and Epson driver. But switching to ImagePrint 10 was a godsend.... custom profiles for virtually every paper and lighting condition, with color and greyscale, and no need to ever touch a color management or printer setting ever again. Just choose paper, profile, size and feed mechanism and IP makes sure every print setting is ideal.

IP is expensive (roughly same as my P800), but on the bright side, I would have had to spend twice as much on custom profiling gear to achieve similar results, and still having to deal with all the possible screw-ups resulting from the Apple/Adobe/Epson chain. I remember well when Apple messed up color management, without telling anyone.

Jeff

Agree 200% after using IP 10 for about 18 months. Just so straightforward to use and fabulous results on the wall.

[Andrew Stupple]

Hi all. I wonder if anyone can advise me. I have DxO 5 and have been using the presets to convert some of my images into B&W. What are the chances of desaturated colour (not true greyscale) issues ocurring in larger size prints?

[jaapv]

Desaturated colour gives sub-par low contrast results. Try Silver Efex. 

[250swb]

And it's always worrying to hear terms like 'true greyscale' because working in greyscale has little to do with true 'B&W' image making. Use Silver Efex and work in RGB Tiff files all the way from the converted RAW file to the print. Using RGB with the specific paper profile loaded into the printer ensures a neutral print if that is what you are after.

[jaapv]

The only thing Greyscale does is to insure  a perfectly neutral file. It is basically the *L channel only. All functions that require colour channels won’t work.

The basic workflow for B&W is to set the correct exposure , set a black point, a white point if needed and adjust levels and curves to obtain the tonality required. If desired the brightness and contrast can be tweaked

Or even simpler, just use the LR. B&W panel in the Develop module. 
The only point where you encounter colour spaces in LR is the Export dialogue