DNGMonochrome: dead pixels          
    Turning Leica DNGs...          
   ... into monochrome DNGs !          

The algorithms DNGMonochrome uses do not automatically map out dead pixels. Since DNGMonochrome doesn't color interpolate and doesn't touch the green pixels in the regular result, dead pixels will show up in the monochrome DNG (especially if the dead pixel is a green one). Lightroom (or any other raw converter) will not interpolate the DNG anymore, so the dead pixels don't disappear.

To address this problem, I implemented a way to store the dead pixels on row and column number. After they are registered, DNGMonochrome will map them out automatically.

I see dead pixels

To register a dead pixel, make sure you have one in sight in the 100% crop of DNGMonochrome. They are spotted easiest on dark underexposed photos and show as a white pixel in the dark. Do make sure it's a dead pixel by checking several photos taken after the one you're looking at. The white pixel should show up on all these photos, at the same position.

Here's an example of one of my dead pixels, spotted in the 100% preview:

Dead pixel!

Click on the button 'I see dead pixels...' and a separate window will open, with the same 100% preview. The dead pixel doesn't have to be in the middle, as long as it's visible in the 100% crop window.

Note: the 'I see dead pixels...' button will be disabled as soon as you select another DNG in the list on the left.

The software will reload the photo and search for the pixel (only within the area of the preview), based on the set threshold (100 to 10000). The threshold is default set to 1000. If DNGMonochrome found the dead pixel (preferably the pixel you think is dead) it will show a little red square around the pixel. If it can't find the pixel (or when it finds more than 10) nothing is shown, and you're instructed to lower or increase the threshold. If you increase the threshold, less pixels will be found. If you lower the threshold, more pixels will be found.

   Found the dead pixel, indicated by the red square...

Press the 'Find' button after lowering or increasing the threshold to search again.

NOTE: This method is no guarantee. If the threshold is set too low for the particular photo, DNGMonochrome might start pointing to healthy living pixels as dead (by putting a red square around them). You have to make sure you're really looking at dead pixels before confirming. So don't panic if DNGMonochrome shows you many red squares, simply increase the threshold.

Confirming the pixels

To confirm a dead pixel, click on the red square. The square will now turn green.

To 'unconfirm' a dead pixel, click on the green square, and it will turn red again.

You can confirm several pixels in one go, if you're sure there's more than one dead pixel in the preview and if DNGMonochrome has pointed them out correctly. Just keep clicking the red squares.

If you see an orange square, it means the found pixel is already registered.

When you're done confirming, click the OK button, and the location of the dead pixels (only the confirmed green squares) is added to the dead pixel list.

   Pixel is confirmed by clicking on the red square (turned green)... click OK to actually register it...

Per camera on serial number

DNGMonochrome stores dead pixels per camera on serial number, so you don't have to worry if you are converting DNGs from several cameras. The dead pixel list is only applied to DNGs of the camera it belongs to.

If you have registered dead pixels this way, the option 'Fix dead pixels' under the 'Quality' heading will become available. It will be turned on by default. And if you turn it off, it will be turned on again after converting a photo.

If the option is not available, it means you did not register dead pixels for the camera the selected photo was taken with.

The dead pixel list

Behind the 'Fix dead pixels' option is a little button (only visible if the option is enabled). Click the button to get to the dead pixel list. The list will hold all the dead pixels per camera, and here you can also remove them by selecting the pixel and clicking the Remove button.

Of course, if you by now have 5 dead pixels on your sensor, photos you took last year might have only 2 or none. If you convert those photos, the dead pixels that are still alive in that particular photo wil also be 'fixed'. But that's hardly a problem, since the pixel is simply avaraged out. It will not be visible that a healthy pixel was 'fixed'.

Something important

The 'Fix dead pixel' functionality does not repair any lines on your photo that might be caused by a dead pixel. Look at this clever utility (not mine and I'm not affiliated with it in any way) if you want a more permanent solution for your color DNGs: Pixel Fixer

The coordinates stored within DNGMonochrome are specific to DNGMonochrome. Seeing how different programs might handle tags as 'ActiveArea' and 'CropSize' differently, the coordinates DNGMonochrome stores might not reflect the coordinates other programs are using to register dead pixels. Don't use the DNGMonochrome coordinate list for other purposes.

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