Adobe Photoshop 4.0.1 Reviewed by Liang-Wu Cai

Since I "converted" myself to a PhotoShop believer, I found, unexpectedly as I have done quite a bit of image processing using a primitive tool known as xv in the Unix world, that the initial learning slope was quite steep, and the feelings at times were uneasy. I wish this brief writing, not really a review, summarizes some of my experiences as a new comer and hope they would be helpful for other new converts.

One thing to keep in mind is that I was already an Adobe fan before jumping into the deep water of Photoshop: I am an avid PostScript programmer, the de facto standard programming language for high-end laser printers. PhotoShop is also the de facto standard image editor for the photography and publishing industries. I've also heard of the "True Type fonts" that redefined the computer fontry... All to Adobe's credit. I like and appreciate very much their works of solid software engineering: you can really feel that their products are well crafted with lots of ingenious thoughts/researches behind them, as compare to others who simply crank out things that are crapily put together to undercut others' market.

I used PhotoShop before, when it was in versions 2.x and then 3.x since I have been in a college environments for too long. I hesitated at that time to jump into it for my humble purpose of retouching scanned images. It changed when I had the chance to set up a digital darkroom, to some extent, and finally to have a copy of this software in my hand. (Price: $200 for the academic edition; about $450 - $500 street price.) Now, there is no point of going back.

Hardware Requirement

I bought the PC version which works under both Win95 and WinNT 4.0. In fact, my PC is Win95/WinNT dual-boot, in which case one installation enables the software to be used under both operating systems. But I have some problem with the display setting with the WinNT, and my dye-sub printer only works with Win95. Hence, I am stuck with Win95, which is quite crapy in my humble opinion. (I'll have a review about my PC later to complete this series of reviews of my "digital darkroom".)

The requirement actually depends on the intended use of the software. The main consideration is the memory size, assuming all computers these days can display at least 256 colors. My experience is that the software is working comfortably fast if you have at least 3-4 times the size of the largest image you want to process. For instance, my largest image is the full-resolution scans: 2700dpi which has the size of (0.95x2700) x (1.45x2700) pixels x 3 bytes per pixel = 30M. To comfortably handle such an image size, I need at least 120M of memory. (My PC has 128M.) Without sufficient memory, PhotoShop will use a portion of hard disk as a "scratch disk" for memory swapping.

I cannot emphasize enough the memory size requirement: when using the "scratch disk", PhotoShop is literally crawling. Actually, the situation is even worse than it appears. Once PhotoShop resources to the scratch disk, it get stuck with this routine even the images size is far smaller than the computer's memory size later on. For instance, when I was processing a batch smaller images (<10M) for web display, I thought I had plenty of memory and I could open up a whole bunch of images at the same time. As the processing went on, at one point PhotoShop started using the scratch disk. Afterwards, even I closed all other images except one, PhotoShop continued using the scratch disk. I think this must be a bug in its memory/scratch management scheme. When this happen and becomes unbearably slow, I have to restart the PhotoShop to get out of this rut.

Monitor Calibration

Monitor calibration is not a trivial task as it seems, or as described in the manual. This is the thing that amounts to my steep initial learning slope. It could be a pains- taking procedure, but it has to be done as the first thing, at all cost! Doing it right saves lots of agony.

The main task of calibration is to set up appropriate monitor gamma value and color balance. PhotoShop has a monitor calibration feature built-in. But one needs to keep in mind that the procedure described in the manual is for printing purpose, not for web displaying. The former is indeed quite trivial if you follow the procedure faithfully.

My trouble started when I began processing images for web display. An image that looks perfect on my PC would look washed-out and even with a distinct colorcast when viewed on other computers. At that moment, I realized that I need a different monitor calibration setting. Fortunately PhotoShop has the provision for saving and loading different calibration settings.

There is no industrial standard for monitor's color displaying characteristics. Since web images will be viewed by all kinds of people using all kinds of monitors, the only sure way is trying to see your images on all varieties of monitors that you have access to. Before going out, adjust your own working monitor to the most comfortable setting, fine-tune an image, and put it up on a web page. Then go out and check out your own image on every monitor: see the difference in color cast, brightness and contrast, take notes and then find the best compromise. Before taking notes, try to adjust the viewing monitor to its most common setting.

Most UNIX monitors have a reset button for the brightness, contrast, color temperatures, and many other things. By all means press the reset button. In addition, some UNIX machines have a provision for adjusting the gamma value. There has been a writing about adjusting the gamma values for different UNIX machines on the net. The common gamma value for a monitor is somewhere between 1.4 and 2.0, with 1.8 being the most common one. For PCs and Macs, modern monitor are much more complicated, you have to play with it a little bit more (assuming this is not your own working PC), such as browsing some photo web pages, then adjust to the best compromise.

With all notes taken, now you can go back to your working PC to adjust the monitor calibration (not the image) so that the image on your working PC closestly resembles what your see on other computers. Save the setting. Afterwards, readjust the image; loop back to the beginning to fine tone the calibration. After the calibration, don't let anyone adjust your monitor's brightness/contrast settings.

Basic Image Processing Tools

PhotoShop provides abundant tools for image processing. Sometime, different tools do essentially the same thing, but in different ways. I am just beginning to learn these tools one by one. Comparing to other image processing programs I have used, I found the following tools to be particularly powerful and useful. At this moment, those are all I need. I list them in a way that they represent a typical procedure of my image processing.

• Cropping Tool: The unusual thing about this tool is that it allows you to crop a rectangular region and rotate this region by an arbitrary angle (<90 degree). This is very useful to straighten out misalignments during scanning while cropping: two operations in one shot.

• Rubber Stamp Tool: Very useful for removing small specks. It allows copying a neighboring region to the cursor position. Much easier than using a painting tool since the color used in the rubber stamp automatically changes according the to specified source as the cursor moves.

• Level Tool: This tool allows one to truncate the pixels' brightness level. It is most useful for setting some dark area into a total black so to avoid showing it in wrong colors, as some low-end scanner tends to do. This is also the primary tool to adjust the gamma value of the image.

• Variations: I found this tool very useful for a rough tuning of the color balance. Basically, the tool shows, in thumbnails, the image compared side-by- side with a set of 6 images with different predetermined but adjustable amount of color adjustments, one + one - for each of RGB channels. You pick the one that looks the best, then it becomes the current and the next set of images is displayed. Thus the color adjustment is done progressively. It also allows saving a setting to a file and be used later. Also, it keeps the same setting when this tool is invokes the next time. Having set up the scanning process to use the same set of scanning parameters (see my review of the scanner I currently use: Polaroid SprintScan 35), this is a tool for doing the color balance adjustment in a mechanical way. But the limitation is that the thumbnail images are quite small, some fine-tuning is still necessary by using the color balance tool.

• Color Balance Tool: To be used for fine-tuning the color balance, in whatever magnification of the image you set. The color balance adjustment in PhotoShop (including the "variations tool") is applied to 3 levels: shadow, mid-tone, and highlights. In most cases, adjusting the color balance for the mid-tone portion of the image suffices for printing purpose. But for web displaying purpose, attentions must be called for the shadows too, since in some monitor displays the image much brighter than your monitor.

• Color Replacement Tool: It allows you to pick a selectable range of similar colors to be replaced. The replacement colors are defined in the HSV color model: different replacement colors are determined by rotating the color hue dial to the specified degree. This tool is useful for filling some burnt-out area with some light colors, or for correcting color cast of unusual light sources, such as florescent or incandescent lights.

• Curve Tool and Color Saturation Tool: These two tools allow direct access to the brightness, contrast and color saturation, within each color channel or over the overall image. But I'd strongly recommend to stay away from these two tools unless other tools have failed. Real pros do not use them. :-)

• Image Resizing Tool: At the beginning, I was quite annoyed by two different sets of definitions of image sizes: over all pixel dimensions and the printed image size. For web displaying purpose, only the former matters. The latter is important for printing, and also affects the way to set the font size. Resizing the image is an important step in any case. When you adjust any of the parameter, watch out the changes of other parameters: some of them you may not want to be changed. If you are going to print an image, check this again before proceeding: I have many times forget to change the resolution and printed the image exactly the size of the slides. :-)

• Sharpening With Unsharp Mask Tool: All scanned images look unsharp. I think the concept of unsharp mask is unique of PhotoShop. This is the very important step toward finalizing an image. The good thing here is that you can play with the parameters and see the effects before making the final commitment. The following is the set of parameters I use.

  	Printing (~2400x3600 pixels)	Web Displaying (~300x450 pixels)
  Amount	150 - 220 %	60 - 120 %
  Radius	1.5 - 3.5	0.5 - 0.9
  Threshold	0 - 4	0 - 2

Long Way to Go

PhotoShop is an extremely powerful image processing tools unchallenged in the industry for many years. I don't think Bill Gangs will ever be able to come up with anything that is remotely comparable with this one.

There are many more tools in the PhotoShop to be learned. I am a slow learner. I prefer to stick with a set of tools and master them before proceeding to learning others. Therefore, it would be a long way to go for me. I'll keep this page updated whenever I have learned and mastered other tools. For a while, the above set of tools suffices for my humble goal of digital image processing.

I might be accused of wasting the power of almighty PhotoShop. That is fine with me. :-) At least, PhotoShop does things professionally and fast. For example, doing an image sharpening using xv on a full-resolution scan takes about 10-20 minutes on a typical UNIX machine. In PhotoShop, it takes seconds!

BTW, I strongly recommend watching the demo CD that comes with the software. That is where I heard the saying that "real pro does not use curve and color saturation tools." :-)