Say I scan a b&w neg in RGB mode. The image comes out, not as a true b&w, but as a slightly tinted, almost sepia image. There is color to it until I convert it to grayscale. So, it is not b&w and it is not sepia. Whatever it is, I really like it better than b&w or sepia. How is it referred to when discussing it with the general public (They have no clue what RGB is)?

This RGB image...I can not say what tint it has because I am somewhat color blind I have a real hard time distinguishing colors of minor intensity Is this a particular tint or are all RGB scans different, based on the particular scanner personality or settings.

RGB = Red, Green, Blue color models (or channels) used in creating the various color pixels within images.

You might have heard or read about people wanting GIMP to have CMYK support which uses Cyan, Magenta, Yellow, and Key (Black) colors, which adds a greater range of colors and vibrancy for printers of professional media.

I believe Kodak (or possibly HP, not sure which) intend to adopt the RGBY color modes (adding yellow to the mix).

I know what it is but I do not know if a rgb scan has a particular color or look or if it is just an arbitrary thing. If I make a print using the rgn scan is there a name for it based on its color appearance or is it just called a "b&w print with a tint"?

I don't think scanners have intelligence that separates the types of RGB scans per image color appearance. I believe its based on the RGB color/light sensors and a set algorithm for converting to greyscale, should the user wish to scan B & W images/documents. It's an "one size fits all" algorithm, but most scanners (the newer ones, at least) give users more control over editing functions, like contrast, lightness, saturation, etc. So, in answering your question in part, the older scanners (including some more current versions) scan in one mode (RGB). A separate algorithm sorts color images scanned as B/W into greyscale. This includes B/W images being scanned as well (they are still being scanned via RGB sensors, but the algorithm converts the image - or - if scanning B/W in color mode, the sensors will sort of "embed" those colors into the image).

I forgot to add one important note: not all scanners work with the same sensor technology and set of algorithms. So results can vary wildly from one scanner to the next. This is important to note, because when choosing a scanner for the type of output desired, you really need to consult with groups who work with that media (i.e. B/W negative scanning, etc).

mahvin has made a couple of posts since I started working on my reply, but I think it still applies.

As if there wasn't enough confusion, the basic color modes can be expanded to include an Alpha (transparency) channel. So you may see a reference to RGBA - which is the Red, Green and Blue mode with Alpha transparency.

As to the slight color you are seeing, it could very well be either the scanner, scanner driver or even the monitor. It is my understanding that professionals have special equipment which they use to calibrate their scanners, monitors and printers so the color values are consistent across all their gear. Heck, it could be that your scanner is picking up and enhancing a color from the negative that you are missing with your eyes.

A long time ago I used to work on copy machines, and there were some that when the lamp would begin to fail would produce copies that had dark banding. It is at least possible that the lamp in your scanner is starting to fail, but this could easily be checked by scanning a blank white sheet of paper and looking at the output on the monitor.

If you want to see what the color is numerically, you could use the eyedropper tool to "get a sample" of the color. This will load the sample color into the foreground color box; then click on the foreground color box and it will show you the numbers being used to represent the color as either RGB, HSV, etc. To produce various shades of gray, RGB color modes output equal amounts of each color channel; the lightness or darkness intensity can be finely controlled by the Value. if there are variations among the RGB channels then the color is not a gray shade. In this image the medium gray is RGB:102,102,102 with an intensity Value of 40; if it were an "off" color then the Red, Green, and Blue channels would not have the same number for each.

Good points, Bob. I didn't want to delve into the transparencies/opacity arena, because I still wasn't sure if I was covering the original question about BW images scanned with a tint. I'm glad you at least touched on it, because it sort of simplifies how colors are converted to different levels/shades of gray based on the sensing of colors and their corresponding lightness or darkness (opacity/transparency).

From a scanning standpoint, depending on your model of scanner and its hardware/software quality, most have auto calibration, some calibrate before scanning. I recall in the college lab, having to insert the rgb and grey calibration sheets manually, what a chore that was (alignment had to be perfect). So more good points about the lamp and tricky negative color enhancing/possible color blindness relationship. There's a whole "down the rabit hole" scenario on the human eyes and what we actually see. This means all humans, not just ones with color blindness.

Sofasurfer, per your post:


This depends on the scanner. Not all scanners are treated equal. It could be either. But like Bob added, if the lamp is going bad or our eyesight isn't up to snuff, it's anyone's guess. It can't be arbitrary if you can make adjustments before or after the scan (within the scanner software). Or at least, that's how I perceive it.



Other than the modes or options the scanner comes with, the only naming convention I am aware of would be those offered by the scanner software. Now, I am guessing (or better said: "I have a hunch") you mean like something similar to a Sepia edit or scan. Then I would have to say no, because in actuality you're just scanning a B/W photo with RGB mode and not converting it to greyscale. The plus side to this, like Bob mentions above, is that it allows you to have a RGB mode B/W image to edit, right off the bat. You can still scan in greyscale mode and convert the image to RGB or RGBA once you open it in GIMP, or other editing software.

As for printing and associating it with a scan mode, it's just a B/W image scanned in color (RGB). Unless you have one of those professional media scanner/copiers with CMYK, then you have it made. I used to run a Xerox color scanner/copier for making brochures and media presentation booklets on a contract job, and the owner told me it cost 5k a month just to rent the machine. Wow!

I hope this helps.

So, are we saying that in a perfect world that a scan of a b&w image will look the same in rgb or grayscale?

Anyhoo, here is a comparison of scans from a photographic graycard, in grayscale and rgb.

The same image being scanned using both methods (color and greyscale) resulting in the same appearance? No.

A color scan of a B/W image or negative will leave a color tint of one or more of red, green, or blue. This depends on how good the sensor and lamp is, whether its calibrated to the best of its ability, etc. My old crappy HP negative scanner leaves all three colors behind. My accountant actually requires me to send her colored scans of my b/w documents in pdf format, and I can see light hues of red, green, and blue all over them. Would I get the same result from a higher end scanner? Probably not. I really don't know the answer to that, just too many variables in play.

Now, I have a question: What are your concerns with scanning BW using color mode?

My accountant swears color scans are more vivid and readable. I can't say that's true, based on her sole observation, but it is interesting, nonetheless.

Maybe to her the RGB scans appear more realistic; even smooth white paper has little nooks and crannies to trap light and bounce it around.

Not really on topic, just thinking aloud here: I know a little of how digital imaging works, but I am more familiar with photocopiers and CYMK color on printing presses where registration of the printing plates on the paper have an effect on image quality. Do scanners detect color on one CCD (or whatever they use), or are there dedicated Red, Green and Blue CCDs? My point is that if there are multiple detectors and one - say the green detector - is slightly out of position, then wouldn't the output show a very slight greenish halo effect? Or if there is something like the color wheel that some digital projections systems use, and the wheel is out of kilter somehow. I just don't know enough about the innards of scanners. My scanner has been jostled so much that I'm surprised it still scans...

That would depend on the scanner/copier.

CCD devices have a lamp and a front surface mirror to direct the image to the CCDs (R-G-B), and CIS (sensors) devices are LED driven with a single RGB (Red-Green-Blue) LED with a rod lens that directs the image to the sensors. I googled this.

CMYK scanner/copiers, I'm not sure about, although I am sure they have the same approach. I'd have to ask my neighbor since he works for Xerox, he'd probably know.

You're right about one of the CCDs not working correctly could possibly offset the color parameters on a scan (but unless you're a skilled technician with a wad of cash, it's cheaper to buy a whole new scanner than to replace those components). With an exception being you had compatible spare parts.

But for the average consumer, the CCD models are the better of the two. CIS scanners are a bit on the short range.

Monochrome.

This is exactly why we should always have back-up. I would have never associated monochromatic colors with a color scan of a black and white image.