AIM FAQ

I have collected some frequently asked questions about the AIM site here. 

Before sending me e-mail please browse through this page.

Is AIM site available as a Book, a PDF document, as a CD or as a downloadable ZIP archive?

AIM is only available on-line, for WWW browsing.

There are not and will not be be any such distribution (like a Book, or a PDF document) that are financially expensive or that are worksome. AIM is free (for the reader) and I try to keep my expenses and the extra work at minimum.

The complete AIM site is over 200 Megabytes, I can not provide it as downloadable zip archive since I do not have that much of free space in the first place. In addition I'm updating the AIM all the time so I would need to update that big zip-archive also, this is not practical.

• For everyone who wants to do accurate, highest quality digital photographic imaging, in what ever area or application. People with consumer grade devices need to do a bit more work in mastering the linear space because the transfer functions of today's consumer grade digital imaging devices are what they are, but linear calibration provides the best possible quality and accuracy for them too. Linear calibration is photometrically correct editing space, the only one that is correct. Similarly linear calibration is the only one that is correct for tri-stimuli color work and manipulation, like RGB or CMYK spaces that all the digital imaging devices and software use.

In what color space the photos on AIM site are?

If not stated otherwise all the directly viewable on-line photos are in nativePC publishing space:

• Trinitron Primaries (these are the most common phosphors used used in the CRT monitors)
• Whitepoint D6500 (this is the daylight, the hue of the actual sunlight at noon).
• Gamma 2.5 (the native transfer-function of the CRT monitors).

Original images (that are offered in ZIP archives) are mostly either in AIM RGB pro or AIM RGB linear light working-spaces with the ICC profile embedded.

Why do you use Trinitron primaries for publishing to the Web?

Because almost all the CRT monitors have either Trinitron or P-22 phosphors (they are very close to each other). So my images do look the same on other monitors also, I only need to apply the gamma compensation. Trinitron color space is  more than plenty for any printer and generally it is as good as any other rationally chosen color-space. The benefit of Trinitron primaries is that the color-space needs not to be converted when uploading to the web. E.g. the Adobe RGB match with high definition television, if the primary destination of the images is a HDTV then Adobe RGB is good color-space to use.

Why do you use D6500 whitepoint?

I use it because: 1) it is easy to set up 2) it is the most common white that we see and 3) there are some trouble with other color-temperatures, I explain it below.

Setting D6500K easily

On a sunny day show full-sceen white (RGB=255,255,255) on the monitor, place it so that you can simultaneously see thought the window and adjust monitor whitepoint of the monitor so that it match with the daylight. This is rather easy to do and gives surprisingly accurate D6500. 
 
Now, printed gray that is composed by CMY inks using D6500 whitepoint will look somewhat brownish when viewed under incandescent lighting, this is a problem with D6500. However in my opinion it is much better to have the system in D6500 (since it is easy to calibrate and very suitable for CRT viewing) and to convert the images to D5000 for printing if necessary. The color gamut of printers are much smaller so the printing quality does not degrade from this. In case the system is in D5000 and the images are then converted to D6500 for CRT viewing then there will be degradation. 

What other reason for D6500

Now, the D6500 = daylight. In a system that is calibrated to D6500 the daylight is the same as RGB code 255;255;255.

With a system that is calibrated to D5000 the white (that is about office fluorescence lighting) is the same as RGB code 255;255;255.

So when two images (indoor and outdoor images) are put side by side then if the system is calibrated to D6500 then the outdoor image is lighter and indoor image is a bit darker since it has only the red histogram full. This is as it should be.

With a D5000 calibrated system the indoor image is lighter (has all channel histograms full) and the outdoor image is darker since only has the blue histogram full. This does not appear natural.

Could you look at this image, explain how to correct/improve it?

• I will see any image if a decent JPEG copy of it is on the browsable WWW. If the copy appears to be challenging then I will download the uncompressed original (if you have provided the link to that), for a closer look. Particularly I do not like to receive any kind of images by e-mail unless distinctly agreed beforehand.

Could you provide general image editing tips/guides?

• Some pages about basic techniques are under preparation but they at very low priority. There are a lot of such guides elsewhere on the Web and in the User Manuals. There will be some more elaborated techniques eventually in the Tech Section.

How can I get accurate colors with this specific type of printer/scanner/camera?

• I simply do not have answers for specific devices since I have no possibility to experiment with them or to read their manuals. The calibration instruction at AIM are generally applicable and that is pretty much all that I can offer. In addition to that you need to take into account (by experimenting or asking from the manufacturer or the distributor of the particular device) the various device specific settings. 

Sometimes I get artifacts in CGI?

When working with Computer Generated Graphics (CGI) a moderate or steep gamma space like 1.25 to 1.8 may be beneficial, especially with gray images that are 8-bit. CGI work is done with chosen colors, chosen colors are always correct what ever the gamma space is. Chosen colors are also used in a gradient fill that is the most common CGI element and a dark gradient fill on a dark background will in fact appear very unpleasant on linearly calibrated system. However when trying to render any sort of natural lighting (or shadows) again gamma space 1.0 is the only one that gives correct result because in the real-life light is linear. Note also that when image editing operations are applied over CGI in a steep gamma space very large gamma induced errors are usually generated.

I see solid pure black areas in channels view when using linear space, why?

Solid black areas are seen in strongly enhanced linear images, it is one of the indicators of high quality and low noise. Often those pure black areas in channels view are incorrectly considered to be as a drawback of linear calibration but it is the other way around. 

In the color channels (red, green and blue) the areas that appear as pure black indicates that the the particular color component in concern (red, green or blue) just does not exist in that part of the image. E.g. if an object or surface is pure red then both the green and blue channels must appear as pure black since red is only red. Or more generally:  In order to show those hues that are composed by only one of the primaries the other two channels must be pure black and to show those hues that are composed by two of the primaries the third must be pure black.

In images that are acquired and edited in a high gamma space the noise creeps up to very high RGB levels and can not effectively be edited away (like it is easily possible in linear space).  Since the high noise is present in the  gamma-images, the areas in color channel views that should be pure black are dithered by the noise and they appear as smooth dark areas, not pure black. But this is not good at all, it is noise, it should not be there.

Would you contribute articles or photos?

• I have plenty of work with the AIM site, so it depends on the opportunity. 

Do you freelance or do other paid assignments?

• In general I do not take paid assignments of any sort. But I will try to help, preferably on the Usenet (comp.graphics.apps.photoshop) or if it is a very interesting task by e-mail.

About Downloading

• Images and graphs that are shown on any WWW page can be be downloaded by clicking them with the right-mouse button. A pop-up menu will open, choose the command Save Image As from the pop-up menu. Please note that all images shown by a WWW Browser are either JPEG or GIF compressed, they are not originals. Here at AIM the originals are often provided for download as a Zip-file containing the original PSD, TIF or BMP image file.
• Zip-files can be downloaded by just clicking the link. A Save As -dialog should be shown but sometimes your WWW browser may give or you the "Warning: There is a possibly security hazard here" -dialog. There is no security hazard in downloading from AIM site, this is a general message from the browser! This dialog gives you two possibilities, Open It and Save to Disk, use the latter: Save to Disk.
• Calibration Chart as the Background image in Windows Desktop. The monitor calibration charts are accurate GIF files. Windows does not accept GIF images directly for the background but one can use the right-mouse-button in Netscape and choose the Set As Background -command from the pop-up-menu. This is easy way to do it and Netscape converts the image properly, (I have no experience about other browsers).

About Copyright Issues

• Please do read my copyright page. 

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