This article originally appeared in TidBITS on 2004-09-27 at 12:00 p.m.
The permanent URL for this article is:
Include images: Off

Editing Photographs for the Perfectionist

by Charles Maurer

I have two modes of taking pictures: point-and-shoot and perfectionist. In the first mode I use a pocket-sized camera with no manual controls. It processes the pictures, I throw them onto my hard drive, and the only editing I'll ever do is remove some occasional red-eye. In perfectionist mode I revert to a previous incarnation and become a commercial photographer again.

This year my perfectionist mode has gone digital and my computer has replaced my darkroom. To effect this change, I reviewed all of the photo-editing software available for the Mac. In this article I shall summarize my take on the most suitable products available for the perfectionist to finish photographs.

Since some readers will come to this from photography and others from computers, I shall not assume that anybody understands the jargon from either side and shall go back to basics frequently. My intent, however, is to point out an approach and products that go far beyond the basics.

The Raw Truth -- The digital sensor in a camera generates a file of raw data that requires an enormous amount of processing to become converted into a usable image. This processing can be done in the camera or by a computer. A computer allows more control and the opportunity to change your mind in the middle.

The conversion of a raw file into an image is not straightforward. Many algorithms are possible, so different programs come out with different results. Try the converter that came with your camera, try Adobe Photoshop, try any others you might have on hand, and see what you like the best. Note that Photoshop and perhaps some other applications will permit you to enlarge the images from the different colour channels to slightly different extents, to compensate for one cause of colour fringing, lateral chromatic aberration. This is useful but don't expect much. Most colour fringing comes from other causes.

Raw files can be converted into TIFF or JPEG. TIFF (Tagged Image File Format) contains full information but is large. JPEG (Joint Photographic Experts Group) is compressed but impoverished. It is sensible to convert raw files to TIFF, keep the TIFF files for editing, then convert them to JPEGs as needed for distribution.

You are likely to be offered the choice of converting your raw files to 8-bit or 16-bit colour. Eight bits ought to be sufficient, but if a picture is poorly lighted or poorly exposed, rescuing it may require teasing apart nearby tones. In that case smooth tonal gradients may break up into discrete bands unless you have more steps. However, 16-bit files are twice the size and take much longer to process. I prefer to use 8-bit colour normally and to take the risk of needing to reconvert a file on the odd occasion that eight bits aren't enough.

Most raw converters allow you to sharpen the pictures. Indeed, most of them sharpen pictures by default. However, never sharpen pictures at this early point in the process. Sharpening of this sort, "unsharp masking," distorts the image at edges, which then prejudices other manipulations. Moreover, the amount that is useful depends upon the size and purpose of the final image. Sharpening an image should be the very last thing you do.

Noise Ninja -- A digital sensor always records a certain amount of random noise. Usually this is an insignificant proportion of the image, but it may become objectionable with long exposures or higher amplification (i.e., higher "film speeds" or "ISO speeds"). It can also become noticeable in smooth areas under ordinary circumstances. It is possible to characterize mathematically the noise produced by any particular sensor at any particular amplification and to subtract that noise from the image. This subtraction needs to be done before you modify the image. However, at this stage in the process, it is important that you remove only noise, not detail. Later, after the detail has been brought out as best as possible, it may seem sensible to remove some of it to clean up some more noise, but that comes later. At this point, you want to retain all of the detail.

I have not tried many noise-reduction packages because wherever I read comparisons, one of them always came out at the top for both Macs and Windows: PictureCode's Noise Ninja ($30 or $70, depending on whether you need 8-bit or 16-bit output). Noise Ninja can discriminate remarkably well between image and noise. I have found that with images from my Sigma SD-10 shot at ISO 100, Noise Ninja's default settings (other than turning off sharpening) eliminate all the noise that ever becomes visible, yet never affects any detail. Noise Ninja has shown itself to be so reliable that I am about ready to start running images through it automatically in batches - but only for pictures shot at ISO 100. The higher the sensitivity, the more noise, so that the difference between detail and noise becomes less clear. Where there is more noise, it is even more important to use Noise Ninja, but I prefer to run it by hand for greater control.


FocusMagic -- Once you've eliminated noise, it's time to wave a magic wand over blurry parts of the picture. If the lens wasn't focused properly or had too little depth of field, or if the subject or camera moved, this magic wand may remove the blur. The wand is Acclaim Software's $45 FocusMagic. It can't produce perfection, but 8" x 10" enlargements can show astonishing improvements.


Although FocusMagic sharpens the picture, it works quite differently from ordinary sharpening routines. Ordinary sharpening routines enhance contrast at sharp edges; FocusMagic forms sharp edges out of blur. Be sure to use FocusMagic before any other optical correction. To fix focus blur, FocusMagic works at least as well as the $60 FocusFixer from Fixer Labs and is a bit easier to use. To fix motion blur, I don't know of any alternative.


Unfortunately, although a stand-alone version of FocusMagic is available for Windows, only a Photoshop plug-in is made for Macs and requires Photoshop; it will not run in GraphicConverter.

A Better Perspective -- Now comes the time to compensate for basic optical problems in the photo:

For these corrections I use a quartet of plug-ins by The Imaging Factory: Debarrelizer, Perspective, Squeeze and Vignette ($40 each, other than the $20 Squeeze). They are easy to use and combined they offer more control with greater sophistication than any similar products I have found, except for one lacuna: they offer no compensation for pincushion distortion. Unfortunately (in this context), I happen to have no lenses that cause pincushion distortion, so products to repair it are beyond my ken. In theory the $40 plug-in LensFix from Kekus Digital offers more precise compensation for distortion and chromatic aberration than any other product but with my lenses I found it to be no better, merely difficult to use.


Asiva -- Up to this point, all of your manipulations are straightforward and mechanical. Now we bring in artistic judgement because we need to adjust tonality and balance colour. The usual approaches to this employ the adjustments built into Photoshop, but I find something else that is easier to use, more subtle, and more powerful: the $70 Asiva Shift+Gain. This is a product fundamentally different from anything else on the market and fundamentally more useful.

< ShiftGainTrial.php>

Whenever you edit a photograph, the first thing you need to do is select the pixels you want to change. Often this means complicated masks and careful manipulations of the mouse. The procedures in Photoshop can be anything but simple, even when they happen to be straightforward. Instead, Shift+Gain will "see" and identify the objects that you want to change much as you see them yourself.

If you can see a face or leaves or twigs or hair, then you are seeing areas of a certain range of brightness and colour. This range must be distinct from what's adjacent, else you would not see the object. If they are different, then the computer can find them automatically and change them.

Incredible as it may seem, the Asiva folks hold a U.S. patent on this idea. Shift+Gain is one of their implementations of this patent. With Shift+Gain you define some arbitrary region of the photo and instruct the program to find and change therein all pixels of an arbitrary range of brightness and colour. If the object you want to change is too variegated to define - well, then you can define the colours of the surrounding objects and tell the program to change all the pixels that it did not find.

Although computers create colours from red, green and blue, and most programs deal with colours as mixtures of red, green and blue, people do not easily conceive of colours this way. It is easier for us to think of colours as having one place on the rainbow, more or less pure or concentrated, and lighter or darker on a continuum between black and white. Those dimensions are hue, saturation and value.

Asiva Shift+Gain lets you think about colours that way. It provides three graphs with hue or saturation or value on the horizontal axis and amount on the vertical axis. You shape a curve on each graph and Shift+Gain selects the colours that fall under those curves. The selection appears immediately. You can work on the whole photo or on regions that you have selected with the marquis or lasso. You can then make changes to your selection's hue, saturation, value, red, green, blue, or any combination of the six. The changes are in direct proportion to the amounts you specify with your curves (Shift). On top of this, they can be made to increase more when the saturation and/or value is greater (Gain).

This is difficult to understand abstractly, and using the product feels strange at first, but it can make sophisticated transformations trivial. A master painter will model his subject in light and shadow - chiaroscuro - and also in colour. Chiaroscuro and colour are limited on canvas. To add contrast, to define a scene better, a painter will mix the two dimensions by colouring highlights and shadows. Photographs have an even more restricted range of tonality and colour, so mixing the two dimensions becomes even more important in photography, but it is usually difficult. Shift+Gain makes it easy.

Look at the sample picture linked below. I took this snapshot with my point-and-shoot camera on holiday then transformed it with Shift+Gain. This transformation could not have been wrought in Photoshop without a lot of skill, but in Shift+Gain it was simple. The highlights were right but the shadows were too dark, so I tried lightening all the tones that were a little above black. That lightened some shadowed leaves too much, so I played with the saturation curve until things looked right, which turned out to mean lightening only weakly saturated dark tones. This left the shadows fine but the mid-tones were still too dark, so I lightened all of the mid-tones. At this point the tonality was okay but the picture still looked flat. It needed more saturated contrast within the midtones - i.e., brighter colours - so I increased ("shifted") the saturation. That didn't look good, so I tried increasing the gain of the saturation, making more-saturated colours still more saturated but changing less-saturated colours less. That was the right direction but the colours needed different amounts of this treatment and saturated blues needed to be decreased rather than increased.

< desertspring.jpg>

Asiva also makes three other plug-ins that offer the same visual method of selecting areas. Correct+Apply Color ($50) replaces one hue with another, or overlays a hue as digital make-up, in both cases maintaining the original saturation and value. Sharpen+Soften ($70) sharpens or softens the selected objects. (Note: do not use Sharpen to sharpen everything. It still isn't time for that.) Selection ($40) creates a selection in Photoshop for use with other Photoshop tools. All four of those plug-ins are excellent products that are convenient to use and work with alacrity. A $200 bundle includes them all. Asiva also sells a $50 plug-in, the just-released JPEG Deblocker, that is designed to enable Shift+Gain to work properly with JPEGs, if TIFF files are not available. I have not tried it.

< plugins.php>

Unfortunately, each of these plug-ins requires Photoshop. Asiva does make a stand-alone application - Asiva Photo - that does the job of all four plug-ins, but I cannot recommend it. I find its user interface inflexible and awkward, and it is so slow that on my 800-MHz Titanium PowerBook G4 I need to twiddle my thumbs for 10 to 30 seconds after every click of the mouse.

Photoshop, At Last -- Finally we have finished our Asiva detour and are ready for Photoshop. This is the point when you can do almost anything else that you want other than enlargement and sharpening. I usually need to retouch out a few specks of dust but not much more. To remove a lot of dust, you might try a free product from Polaroid, Polaroid Dust & Scratch Removal; it's available as either a stand-alone program or a Photoshop plug-in.

< FOLDER%3C%3Efolder_id=2534374302023779& amp;PRODUCT%3C%3Eprd_id=845524441760086>

PhotoZoom and the Finishing Touch -- If you want to crop your photo, crop it now and save the cropped file under another name. When you want to make an enlargement, enlarge the file in Shortcut's $50 PhotoZoom or $130 PhotoZoom Pro to create a new file with the optimal number of pixels for the size of print and the resolution of your printer. By default, both of them sharpen the photo too. This, finally, is the time for sharpening and I have found one of their default settings nearly always to be appropriate, although occasionally I have wanted some of the fine-tuning available in PhotoZoom Pro. These products are significantly better than any other enlarging package for the Mac. I've found PhotoZoom Pro 1.0.95 to be buggy, but it makes such superb enlargements that I have not regretted its purchase. Finally, if the enlargement turns out to show too much noise, open the enlarged file in Noise Ninja and optimize it.


With dye-sublimation printers and some inkjet printers, it is possible to send the printer a file prepared in PhotoZoom that defines precisely every pixel that the print-head is to print. On my Olympus dye-sub printer, this technique generates photos that are strikingly sharper than any I get by sending the printer a smaller file and having the system software fill the page. Unfortunately, most inkjet printers do not have a fixed resolution, so the printer's software has to fudge whatever file you send it. If the printer's specs show a number of pixels or dots per inch that is somewhere around 300, then it probably has a fixed resolution of that number; if its specs show dots per inch in the thousands, then the number bears no relationship to the resolution you will see. Indeed, in this case the resolution of the print is likely to be undefined and variable.

To understand this, consider a printer that prints 1,440 dots per inch. Each colour of ink is laid down as individual dots and the dots cannot overlap. One dot from each ink required to produce a colour is the number of dots required to form the smallest possible bit of that colour; i.e. a pixel. If different numbers of inks are required to form different colours, the number of dots per pixel will change with the colour. On top of this, the dots are likely not to be laid down in a fixed pattern but scattered about stochastically.

If you are unhappy with your printer's sharpness, then you might try testing it with files created at different resolutions, to see if one of those files prints better than the others. If it does, then you are likely to get better results by feeding your printer files of that resolution. I made a few test files for this purpose; download them in the Zip archive linked below. These are 1-, 2- and 3-pixel stripes with headers showing different numbers of dots per inch. Print them with Photoshop or GraphicConverter, not Preview, because Preview will change the patterns' sizes to make them fit the paper. Examine each one to see how smooth the patterns are; if one particular resolution prints better than the others, then scale your photos using that number of dots per inch. However, do consider that what matters is your photographs, not tests. This test can make any printer look bad. If you are satisfied with your printer's sharpness, there is no point to investigating this particular bit of imprecision. It would be better to let ignorance remain bliss.


On the other hand, for everything else involved in printing colour, ignorance is not bliss. With most aspects of colour, it is useful to know the slop in the system, so that you know when you need to be precise and when there is no point to trying. To this end, my next article will introduce you to the wonders and absurdities of colour and ColorSync. It will show you a few simple things that matter and describe a world of complexities and costs that you can ignore.

PayBITS: If Charles's recommendations for perfecting photos
helped, he asks that you make a donation to Doctors Without
Borders: < />
Read more about PayBITS: <>