To scan B+W negatives in colour or grayscale?

[bomberman]

I've been scanning all my black and white film in, erm, black and white! ie. greyscale. But I've just thought....... dosen't this rob me of the natural tones that are in the film?

Tell me if i'm being a plonker :shrug:

 

[menthel]

Scan greyscale. There should be no tone lost, the only thing you would lose is any colour cast from the film or the scanning process and that you would ahve to get rid of in pp!

 

[mustanir]

Greyscale every time. Unless you like colour casts or using more disk space per image than necessary.

 

[Musicman]

I scan monochrome images in colour with my Epson V700, then use the extract the sharpest RGB channel in Photoshop (usually the green one but not always) to create a final greyscale image.

I got into this habit as I have a sneaky suspicion* that a greyscale scan uses all three channels, which leads to a compromise in image quality - there's sometimes a small focus and/or registration difference between them in the colour scan (might be CA due to the scanning bed glass and/or due to the fixed focus on the V700).

None of the above may or may not apply if you're using a dedicated film scanner or even something other than a V700.

* ISTR running some comparative tests when I first got the scanner that convinced me that this was the way to go.

 

[menthel]

I scan monochrome images in colour with my Epson V700, then use the extract the sharpest RGB channel in Photoshop (usually the green one but not always) to create a final greyscale image.

I got into this habit as I have a sneaky suspicion* that a greyscale scan uses all three channels, which leads to a compromise in image quality - there's sometimes a small registration difference between them in the colour scan (might be CA due to the scanning bed glass and/or due to the fixed focus on the V700).

None of the above may apply if you're using a dedicated film scanner or even something other than a V700.

* ISTR running some comparative tests when I first got the scanner that convinced me that this was the way to go.

I tried this as well but couldn't detect any real benefit over scanning in monochrome.

 

[Musicman]

I tried this as well but couldn't detect any real benefit over scanning in monochrome.

Well, I see a noticeable difference in the output on each channel from the scanner and with the limitations of a flatbed I'm keen to extract every milligram of extra quality I can.

On a side note, when saving a RAW output scan file with Vuescan, you get a 48-bit colour image, regardless of whether the rest of the scan settings are colour or monochrome, which further suggests all three channels are scanned and then combined to form a final greyscale in the scanner software.

further reading

http://www.largeformatphotography.info/1800F-bw.html

http://home.people.net.au/~cjeastwd/digital/epsonProblems.html

 

[steveo_mcg]

Is it possible to extract a single colour channel in Light room? Don't fancy having to work in GIMP for a full load of 35mm scans...

 

[Musicman]

Is it possible to extract a single colour channel in Light room? Don't fancy having to work in GIMP for a full load of 35mm scans...

Not exactly. You might use the B/W sliders and select only Green, but as LR is non-destructive, you'll end up carting two channels' worth of redundant colour information round in the file.

Easy enough to separate out the channels with GIMP if you don't have PS

http://docs.gimp.org/en/plug-in-decompose-registered.html

If you know your way round the command line, it ought to be possible to get GIMP to do it for you automatically - it's eminently more scriptable than Photoshop.

 

[steveo_mcg]

Ah cool. I might look into scripting. Would be easy enough to dump the scans into a folder then have GIMP run through that folder and extract the green channel.

 

[s162216]

If you use Vuescan then if you use the drop-down marked "Make Grey From" (if I remember correctly), the you can set it to make grey from any of the colour channels or Auto which uses a 60/40 split between the green and red channels I think it is.

I scan in colour simply because I have a set of Kodak photo-shop plugins that are very useful for and optimised for film restoration/improvement (ROC, GEM, SHO, GEM Airbrush) and these only work on RGB images so I scan in colour and after using them can down-convert if necessary (and is less destructive than up-sampling to RGB and then back again)

 

[bomberman]

Thanks for the info, i usually create B+W from colour digital by decomposing to RGB and reducing most of the red layer opacity but i wondered if each B+W film might have differtent tone characteristics that i was overlooking. I suppose it would only make a difference if i weas using split-toning (which i don't actually know how to do [but would love to try!]).

 

[Ambermile]

Not being a PS user - rather I prefer the PIx3 from corel - it may not be the same but I would always scan in colour simply because a greyscale image has maybe half the processing options of a colour one. Go to greyscale after you have processed would be my advice, whether it be channel extraction or otherwise.