Photoshop DIFF Action

Followup to earlier post. I found some errors eventually, and have I think improved it some.

I have a bit of a fetish for “lossless editing”working on a photo in such a way that I don’t change the initial set of bits that I imported. I think as you get more experienced it becomes less important; being sure you’ve got something the way you want it means you don’t care whether it’s easy to change later. But, for me, I edit incrementally, taking a while to see the flaws in older edits (especially when I’m editing a bunch of photos that will be displayed together), so it’s very useful to be able to very easily change my mind about things I’ve already done.

So, I use adjustment layers a lot, and adjustment layers with layer masks (which, I say again, are dodging and burning died and gone to heaven!), and then do a lot of pixel fixing writing onto a separate layer.

But there are a few tools, or a few situations maybe, when that’s not the best option. Keeping an entire clean copy of the base layer meets my criteria, but it kind of doubles the file size (layers that are mostly transparent compress pretty well, so my multi-layer files are mostly not that much larger than the base).

So, here’s what I do:

  1. Duplicate the base layer (shortcut: CTRL-j). My process expects the mode of this layer to be “normal”.
  2. Select this new layer
  3. Do the editing that has to be done in the context of all the pixels
  4. Usually, I keep this for a while, until I’ve printed or put the picture on the web or whatever the plan was
  5. Select your edit layer, and run my magic diff script. This deletes every pixel in the edit layer which is the same as is rendered by the stack of layers under it.

So, how does this version of the diff script work? I’m glad you asked!

Listing of diff action
The DIFF Action
  1. Set mode of edit layer to “difference”. This shows the differences between the current layer and the stack under it.
  2. Select all
  3. Copy Merged. This copies the full detailed differences.
  4. Select none
  5. Set mode of edit back to “normal” on this layer
  6. Create new pixel layer
  7. Paste (puts the differences here)
  8. Threshold, level=1. This reduces the difference map to black-and-white, with every unchanged pixel black and every changed pixel white.
  9. Select all
  10. Copy
  11. Delete layer (same one we created above, that was scratch workspace)
  12. (We are now on the original edit layer again)
  13. Set quick mask mode
  14. Paste
  15. Exit quick mask mode. The B&W change mask we made is now a selection.
  16. Add layer mask. The current selection will be put in as that mask. So now we have the edit layer, with a layer mask selecting only the changed pixels on this layer.
  17. Apply layer mask. This deletes all the pixels blocked by the layer mask, and then deletes the layer mask itself. Thus making this layer take a lot fewer bits to store!

Signs Over Windows

The Princess Bride
The author in front of the rubble of Uncle Hugo's Science Fiction Bookstore, wearing a Have Spacesuit, Will Travel t-shirt

In the aftermath of the Minneapolis Police killing George Floyd, Minneapolis has experienced much distress. We’re being forced to confront issues we’ve let slide for too long (or that our work has not usefully improved). There is a huge amount of anger of course, both immediate and accumulated over decades and centuries. There is despair. There are even some tendrils of hope.

I’m not a suitable person to deal with the big issues here. I’ll keep listening, and I’ll keep voting and pressuring my representatives to do what seems right, but I’m not a leader in any of this.

But the visual changes to the city around me are striking. In some areas, most businesses have put plywood (or OSB) panels over all their windows and other glass. That by itself is a big change, but not visually very interesting. However, many of the panels have been painted with slogans and war cries, straight-forwardly or artistically, or even graphic art. Both the text, and the appearance, have been catching my attention, so I started photographing these decorated panels.

This gallery is early versions of pictures I’m working on. They may appear, change, even disappear, as I see fit, while sorting and editing and arranging. Things will probably not be in the best order. There will be duplicate (or very similar) images. There will be missing, bad, or intrusive caption. Also kind of a torture test for the WP gallery feature; we’ll see how that goes.

Updates: 12:50pm 13-June-2020, 0:12am 10-June-2020, 9:10pm 8-June-2020, 10:24pm 7-June-2020, 9:36pm 6-June-2020, 2:33pm 6-June-2020, Noon 6-June-2020

Also, if I get enough photos I like, I will need a name for the project. My first round of ideas doesn’t bear talking about. My second round get some additional meanings to come forward, but it’s not enough yet, the meanings are right but not complete. So, I’m not calling this project “Signs of Distress”. (It doesn’t hint at the hope that’s in some of them.)

46 Minutes of Your Time

Many of you won’t care, but some of you desperately need to spend the time to watch this video.

It’s Ctein demonstrating actual dye-transfer printing (to Michael Reichmann of the photo website Luminous Landscape).

Many of the interesting parts of the process are done in normal room light, so you get to see the real thing, and you see the equipment and hear about the process for the bits done in the dark.

Watch this!

And, we’re coming to the end of the sale on the remaining inventory of Ctein’s dye transfer prints, info here.

Probably the Last Ctein Dye Transfer Print Sale Ever

All my life dye transfer has been the top color photo printing process. And for a long time I’ve been privileged to be a friend of one of the very few people who ever did dye transfer printing.

Kodak discontinued the materials in 1994, and Ctein finally closed down his darkroom in 2013. There have been a couple of print sales along the way, too. This one is probably the absolutely final one. This is selling off all the prints remaining in inventory.

Here’s the official press release on it. Note that the first URL given is the top level of The Online Photographer; you’ll need to check “Recent articles” in the left column to find the print sale post when it goes up on Black Friday.

Expert West Coast Photographic Printmaker to Liquidate His Entire Inventory of Rare and Prized Color Prints

San Francisco area photographer and master printmaker Ctein is offering his entire lifetime archive of rare traditional dye transfer prints for sale. The sale will take place on The Online Photographer website ( starting at noon Pacific Standard Time on November 29th, the Friday after Thanksgiving, and continue for seven days only.

Ctein (his only name—pronounced “kuh-TINE”) is selling full-sized 16×20-inch dye transfers for only $650 per print on a first-come, first-served basis. More than 250 images will be offered. Interested readers can view these in advance at

Ctein, among the best-known and most accomplished of the dye transfer printers, worked in the medium for 40 years until he closed his darkroom in 2013. Now, connoisseurs can own a beautiful, genuine dye transfer print for their own collections.

Dye transfer, widely acknowledged to be the Rolls-Royce of traditional color printing methods back in the era of film photography, was extremely difficult to master and expensive and time-consuming to practice. Dye transfer prints have a distinctive beauty and purity of color. They have a greater color gamut and deeper maximum black than even inkjet prints, and were among the most permanent of all color processes.

Such prints were always rare and always expensive, and master printers in the medium have always been few and far between. By 1994, when Kodak finally discontinued making the materials, most of the active dye transfer printers in the US could fit in a single living room. Now a scant handful are left.

For more information, please contact Ctein at or Mike Johnston of The Online Photographer at

Somewhat Snarky Observations About Post-Processing

Now and then I see people claiming it as a virtue that they don’t “do anything” to their photos after they come out of the camera.

Like most religious wars, neither side is totally lacking in value.

Ansel Adams said “Yes, in the sense that the negative is like the composer’s score. Then, using that musical analogy, the print is the performance.” (Sheff, David (1 May 1983), Playboy Interview: Ansel Adams, p. 226) With film, the negative doesn’t look anything like the final image (true enough in black and white, far more true in color), and everybody understood there were decisions required to get from there to a print. Everybody knew it was very important who did your printing (and many people did their own printing in the darkroom, at least until they got successful enough to hire a first-rate printer to work for them).

The actual data recorded by a digital sensor is even less like an image that could mean anything to a human—the Bayer filter array records each pixel in one color, and those are then combined with complicated algorithms to make a color image of the result. But software to do that is built into our cameras, so it’s possible for people who are ignorant of that (or just haven’t thought about it much) to have the idea that the JPEG that comes out of their camera is what the sensor actually captured and any change from that is a distortion.

Okay, it’s time to strip off a couple of important but unusual branches of photography explicitly. In scientific, forensic, and probably some other specialized branches of photography one is basically recording data rather than making images. The photographer needs to be prepared to argue (or formally testify) that the image accurately represents reality in the specific ways that matter (and may wildly distort other aspects of the imaging if necessary to make the thing they’re illustrating more clearly visible in the images). These are extremely valuable, important, areas of photography, but they don’t participate in stupid arguments about “altering” photos; they have clear formal standards and principles, and they’ve had them for many decades.  This argument isn’t relevant to them.

The experience of actually being in a place, seeing it with your own eyes, is complex and largely synthetic (built up in your brain).  We see full resolution with only a small portion of the retina, but the way the eyes move around and the brain treats the results makes us feel like we perceive precisely everywhere.  Our eyes can see detail in a vastly greater brightness range than cameras can, and that also enters into our perception.  It’s usually desirable to print camera images so they resemble what we think we see, rather than what we actually see at any one point in the scene.

One of the most obvious areas is white balance. Leaving the camera on “auto” white balance somewhat masks the issue (letting the camera make what is essentially a post-processing decision in digital), but it’s quite common to want to make the color captured outdoors in open shade look much more like the color captured indoors under incandescent light than it actually is. This can be done more accurately in post-processing generally than by relying on “auto”.

Every single scene you stand in front of doesn’t look best cropped to 4:3 (or 3:2 or 6:7 or 16:9 or 8:10). Making a fetish of “not cropping” (by which people mean cropping only in the camera and hence always using that exact aspect ratio) will make your work less good. (With miniature cameras, especially 35mm and smaller, and early digital captures, cropping too much could highlight technical issues (grain, etc.), and it was good practice to try to frame tightly to minimize cropping later, yes. But that’s “try” and “minimize”, not make a fetish of completely avoiding.) Mind you, the look of prints with a natural black border from an oversize negative carrier really is rather nice.

When photographing a static scene with a long span in time, it’s useful to make precisely-exposed images that capture the scene as well as possible. This saves some time later, and results in better technical quality (often just very slightly better, but sometimes vastly better). And old slide photographers who projected their original slides (that is, amateurs) were very aware that there was no option for them to adjust exposure later, or cropping either.  However, those of us who photograph dynamic scenes, perhaps with changing lighting as well, and us moving through them constantly would frequently miss our best shots if we took the time to get perfect exposures each time. Yes, as we get better we judge the exposure better by eye, and just work faster, and that has technical benefits to the work that are not to be despised; but the ability to shoot quickly is very often the difference between a brilliant picture and a useless picture in dynamic situations, and using post-processing to make that brilliant but technically somewhat under-exposed picture look excellent is IMHO entirely appropriate.

Making exhibition-grade images often involves a lot of local brightness adjustment—”dodging” and “burning”, deliberate “vignetting” (or correcting corner falloff in your lenses; the opposite of vignetting), gradient filters (and people used split neutral density filters on their lenses when taking film photographs sometimes, especially slides, because of the narrow brightness range they could capture), and so forth. Darkening areas to suppress distracting detail, creating brightness patterns to lead the eye, emphasizing the important features.  Pablo Inirio was the master printer of Magnum Photos for decades, and Magnum has released a few of his annotated workprints for printing important photos.