Preserved Topic: Color balance for B/W photos (Page 1 of 1)

1. Should I scan a B/w photo in RGB or B/W?
2. After scanning the photo looks great on the screen, but prints with either a green or red hue.
3. I have adjusted curves and balances, however, i am seeking the setting that would be consistant for all my B/W photos.
4. Do I utilize the eye dropper options in Curves and Balances?
5. Is there a field where I can plug numbers in to create the perfect B/W balance?
6. If so..where would I plug these numbers in?
I hope that you understand my problem, because I need a solution.

thank you! Thank you! Thank you!!!!



~denise~

i don't know if i understand you but try: image--->mode--->grayscale


CELL 557

It depends. If your black and white photos are perfectly grayscale, B/W scanning isn't a problem. however, if you have brown/sepia toned photos, you can often manage to get more detail out of it if you scan it in color.

If your photographs aren't exactly black and white when you print them, try converting them to grayscale before printing (image>mode>grayscale) or image>adjust>desaturate. If the photos still look weird it's propably your printer. Check your printer software, and look for a setting which tells the printer specifically to print in black and white. It's always best, by the way, to tell us which kind of printer with which operating system you use.



edit: spelling

[This message has been edited by mahjqa (edited 07-04-2002).]

This might help!

http://www.gurusnetwork.com/tutorials/photoshop/curves1.html

AS Mahjqa said, how to scan them depends on how truly balck and white htye are. In general, I go with color either way, then convert to greyscale or desaturate in PS.

As far as a setting that will work best for all B&W photos...there's no such thing. Each photo can be vastly different original contrast, tonal values, color erros, etc., so no one solution is going to work for everything.

The link to the curves tutorial is an excellent one - use it.

I would also highly recommend playing with Levels adjustnents.

as above, but also take a look at the 'channel mixer' as an alternative.

Personally, I find that it's better to scan in RGB, even if you intend to output in Greyscale.
I realise this is essentially what DL-44 just said, but here's an explanation as to why...

Greyscale is limited to 256 shades (if I remember correctly).
RGB contains millions.

To make greyscale RGB: >Image >Adjust >Hue/Saturation
Take saturation down to -100
You will have a B&W looking image, with lots of lovely mid tones.

A quick way to convert color images to greyscale (works better than just choosing image->mode->greyscale)
Image->Mode->Lab color
delete channels A and B
Image->Mode->Greyscale

Converting to Lab color first makes for smoother transitions in the final greyscale image. You can see this by pulling up the Levels display after conversion. Converting to greyscale directly makes for a 'rougher' levels display than before the conversion. Using the Lab color method preserves the smoothness of the levels curve, indicating that the variety of shades is roughly the same.

I used to produce a magazine containing lots of greyscale pics (business was too cheap to print in colour) and most photos I received for scanning were in colour. I have a greyscale tone step 'wedge' from Agfa, which basically is a strip of photographic paper printed with 20 shades of grey from black to white. These are also available in colour. I would lie the strip alongside the photo and scan it (always in colour - you get far more detail that way) together with the photo.

When I opened the scan in Photoshop, I would set my black and white endpoints using the image of the scanned wedge (explained shortly). This is done because you want to be able to differentiate between say 90% black and 100% black in the final printed piece, which if the endpoints are not correctly set, tend to look the same shade. Same goes for the lightest parts of the photo. In other words, you retain details in the highlights and shadows of your photo.

The 'highlight' (white) and 'shadow' (black) endpoints of a digital image refer to the brightest and darkest tonal values in an image still containing detail. An image intended for output to print needs to have the original's white and black endpoints 'remapped', setting the image's brightest value to darker than white and the darkest value to lighter than black. This compresses the tonal range and ensures the lightest details don't drop out to white and the dark details in the shadow areas don't become solid black when printed. (The white and black endpoints define the values that should print as pure white and black respectively).

In Photoshop, open your scanned photo + wedge, go to Image>>Adjust Levels, then click on the white eyedropper. Move the cursor to your photo and click on the white end of the wedge (if you don't have a wedge, choose the whitest part of the photo) and click to set the endpoint. If you have the 'Info' box open - Window>>Show Info - you can check the K (black) values as you move around the photo. The lightest part will be where the reading says 0%. Then click on the black eyedropper and choose either the black end of the wedge - or where the Info box gives you the highest K value in the photo. Pure black will give a 100% reading, although this is rare to find. Go for the highest value you can find in the photo. Click and this sets your black endpoint.

Obviously, you must select your endpoints in that area of the photo that will not be cropped out (if not already cropped in the scanning setup). Also, when choosing the white endpoint, do not choose any area where there is specular highlights i.e. where there is refelected light from the sun in a bumper bar or sunglasses. The overall picture will become too dark. Some scanners will allow you to set the endpoints before scanning. The same process can be (sort of) achieved by sliding the input sliders in the histogram in Photoshop inwards to where the tonal extremes of the photo are (if the histogram indicates a gap between the outermost vertical bars - can happen either end - and the outermost edge of the full spectrum).

You can also adjust the tonal range in the midtones (the gamma point) by going to Image>>Adjust Curves, and pulling the midpoint of the graph to the right to lighten midtones and the left to darken them. This can often compensate for exposure problems in an original photo and bring out more detail, and also restore contrast in an image 'flattened' by endpoint adjustment.

There is no way to automate this process, as every photo is different, with different shadows and highlight points.

(Thanks to my 'Scanning 101' lecturer for this).

well before converting to grayscale check all 3 of your channels. Sometimes (63.45834896723% to be exact) you will find one of the channels to have the best balance for a grayscale image. Just use that channel and toss out the others. If they don't then go with converting the image to grayscale.

23.45% of all statistics are made up.


mahjqa... I love your sig!!!

You may want to calibrate your system with a colormatching product as well. I think Photoshop 7 comes with one but I'm not sure.