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Why Use Greyscale?

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  #1  
Old 03-20-2002, 10:57 AM
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tjsgarden tjsgarden is offline
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Why Use Greyscale?

I am new at photo restoration but sincerely trying to learn the art and skills of photo manipulation.
I notice a lot of individuals convert color and b&w images to greyscale before making adjustments. I am confused about this operation. What is the advantage and why do many individuals make this adjustment before applying enhancements?

THANKS,
John
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Old 03-20-2002, 11:58 AM
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I can't for the life of me think of one good reason to convert to greyscale.
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Old 03-20-2002, 12:57 PM
George George is offline
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If I want to change a color photo to a black and white photo I make use of the grayscale. It gives me a much better black and white photo.

I change the RGB Image to a LAB color photo. I then click on the LAB b channel and drag it to the trash, this allows photoshop to change the remaining two channels to Alpha 1 (lightness) and Alpha 2 (LAB a). Then click on the Alpha 2 channel and drag it to the trash leaving only the Alpha 1 (lightness) channel.

The Alpha 1 (Lightness) channel describes the brightness of the pixels from dark to light, and will give you a perfect grayscale image.

Select Image menu and choose Grayscale from the fly out and you now have a grayscale image containing the correct amount of highlights and shadows.

Take a color image, convert it first to grayscale using image mode, save it, then open the original color image back up and convert it using the above process. Get both images opened on the monitor at the same time and I believe you will immediately see the difference in the two images.

George
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Old 03-20-2002, 01:18 PM
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There are quite a few methods for getting a good greyscale image from a color image, but I don't think that was the question. I believe he was asking when would be an appropriate situation where converting to greyscale (grayscale?) mode would be advisable.
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Old 03-20-2002, 01:30 PM
George George is offline
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When converting a color image to a black and white.
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Old 03-20-2002, 03:00 PM
G Mantero G Mantero is offline
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I can't think of any reason to convert to greyscale either, unless you want a B&W photo, and then I'll usually use the channel mixer so I have more control.

Sometimes, I'll make adjustments to only one channel (which show as greyscale onscreen....could that be what you mean, John?

As far as converting to greyscale for any other reason? Can't think of any.
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Old 03-20-2002, 04:03 PM
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I guess I'm being too subtle:

Converting over to Greyscale mode is a destructive, irreversible, and needlessly clumsy method of viewing your image as b/w. There are many preferable methods that will preserve the original data, and simultaneously provide greater control over the process.
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Old 03-20-2002, 04:31 PM
admin_fff admin_fff is offline
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Hello-

I'm definitely a newbie when it comes to photo restoration, so I'll ask the dumb question. (Actually, my fiancee does all the restoration, I just look throughout the net to try to find "tools" to help her along)

Doug, you mentioned in your last post that simply taking a photo and converting it to greyscale is a "needlessly clumsy" method. I was wondering if you could elaborate on a more "preferred" method of obtaining the same result.

Last edited by admin_fff; 03-20-2002 at 04:41 PM.
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Old 03-20-2002, 05:13 PM
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A couple of excellent methods were mentioned up above ^^^, including my personal favorite, channel mixer.

In many cases, the decision is taken out of our hands when scanning b/w originals. Usually one of the channels is so much better than the other two there's no real reason to keep them around.

My favorite short-term method is simply a hue/sat adjustment layer with saturation turned all the way down. This leaves the original untouched, and still lets you have your b/w image.

The most important things are to not discard data before you're positive it won't be needed, ever, and to engage brain instead of trusting any of the 'auto' controls.

Plus gs mode is only one 8-bit color channel, which will necessitate conversion right back to RGB for many operations.
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Old 03-20-2002, 05:50 PM
admin_fff admin_fff is offline
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Doug-

Thanks for the response. I should have read George's post a little more carefully. I'll have to give that method a try.
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