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jlw
04-21-2005, 15:31
We've had some discussion here about R-D 1s showing "hot pixels" at high ISO settings, especially when shooting in JPEG mode.

Since I've never owned a digital camera that didn't have a few hot pixels, I haven't been getting into too big a sweat over this. However, this week, as I confront a batch of several hundred JPEG images all shot at ISO 1600, and contemplated the tedious chore of spotting out the same two or three dratted hotspots on every @#$%ing one of them, I decided to try a trick I've used in the past -- and it seems to work! Here's my three-step program:

Step 1: Make a 'hot pixel map': Set your R D-1 to JPEG mode, ISO 1600, and a shutter speed of 1/2000. Shoot a frame with the lens cap on. Load this frame into Photoshop and convert it to grayscale, then open the Levels dialog. Move the dark-clip point to the right so the blacks are solid black, and the highlight-clip point to the left until the hot pixels look nice and white (but not so far that you lose the gray fringe pixels around them; you need these for a natural-looking fix.) Save this image as hot pixels.psd, but leave it open; you'll use it in Step 2.

Step 2: Apply the map to an image: Open an R D-1 JPEG image that was shot at the same ISO you used to make your map. The JPEG should be completely untouched as it came from the camera -- if it's been cropped, rotated, etc., the map won't match up to the hot pixels anymore. Load your hot-pixel map using the Select>Load Selection... command; check to make sure that the hot pixels are selected. At this point you may want to modify your selection; I use the 'Feather' command with a radius of 1 to blend the selection into the background a bit.

Step 3: Filter to fix the pixels: Use the Dust and Scratches filter to repair the hot pixels by interpolating from the data around them. I've been getting good results using a radius of 3 and a threshold of 0. Now deselect; you should see that your hot pixels have been neatly patched.

Now this may sound just as tedious as fixing all the hot pixels individually with the Healing Brush -- but the advantage is that you can automate this procedure using an Action. This lets you start Photoshop churning on a whole folder full of images and spot out the hot pixels while you go do something else.

I'll attach an action to this message with the settings I've been using, along with some before-and-after pix.

You may want to experiment with different settings -- different feather radius or Dust and Scratches settings -- and please post your results if you find better ones! As I said, I just started to experiment with this.

WAESHAEL
05-06-2005, 03:11
I was disappointed to find that no two images had "hot pixels" in the same place. Maybe there's dust on the CF card (hi hi). But the impact on images taken with normal exposure is minimal - perhaps one hot spot if I look carefully. I did the tests you described on A Canon G5. The dark field test I repeated and the highlited pixels were located in different spots on each image.

David Kieltyka
05-06-2005, 09:32
My R-D1 also has no consistent hot pixels. Since there are only a few at most, and only in ISO 1600 photos, I've just cloned 'em out when necessary. The RAW Shooter Essentials converter does a good job of zapping them automatically too.

-Dave-