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DPChallenge Forums >> Tips, Tricks, and Q&A >> Histograms and hot pixels
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06/27/2005 07:45:12 PM · #1
I'm relatively new to this forum and have entered a few challenges already, but I have a couple questions.

1. Is it OK to adjust or 'equalize' the histogram for basic editing?
2. After my first photo submission, I got a comment that my camera seems to have a few hot pixels. I took a closer look at some other photos and realized I have about a half dozen. Can this be repaired or did I just find a good excuse to get a new camera? By the way, can anyone explain why the pixels go hot?

Thanks,
stringofpearls
06/27/2005 11:37:04 PM · #2
Adjusting histogram is fine.

As far as the hot pixels, I don't think there's a way to fix them. Not sure what makes them go hot.
06/28/2005 12:55:58 AM · #3
Originally posted by stringofpearls:

I'm relatively new to this forum and have entered a few challenges already, but I have a couple questions.

1. Is it OK to adjust or 'equalize' the histogram for basic editing?

It depends on how you are 'equalizing' the histogram. If it's by levels or curves it would be fine as long as it is done in normal blending mode in an adjustment layer or on the original layer.

It's possible to go to far with this as it is with anything.

Originally posted by stringofpearls:

2. After my first photo submission, I got a comment that my camera seems to have a few hot pixels. I took a closer look at some other photos and realized I have about a half dozen. Can this be repaired or did I just find a good excuse to get a new camera? By the way, can anyone explain why the pixels go hot?

Thanks,
stringofpearls

Not being able to removing hot pixels, sensor dust, lens dust, etc. is an often lamented restiction of the basic editing rules.

The only way I know of to remove hot pixels is to use the dust and scratch filter or something similar. They are allowed by the "...reduce the effects of noise, scratches, etc, are permitted." clause in the filters section of the rules.

Hot pixels get hot because they are the weak link (so to speak) -- in the same way a chain will not be made of links that are all exactly the same strength, so are the pixels in the sensor not all the same strength. Long exposures are the most common reason for them.

David
06/28/2005 02:25:06 AM · #4
There was a russian programmer that had a hot pixel remapping software out there for Nikon. Not sure if he has it for Canon. I'll make a quick search
Edit: For Nikon, but look at these
//www.tawbaware.com/pixelzap.htm
//www.starzen.com/imaging/deadpixeltest.htm
//www.mediachance.com/digicam/hotpixels.htm


Message edited by author 2005-06-28 02:37:57.
06/28/2005 07:21:18 AM · #5
AFAIK, Canon can remap the sensor. I had Nikon do so on my 995, which elimited several bad ones. Whether it's worth having it done is another question that only you can answer. I sure wish that camera manufacturers would make those utilities available to those who need them.
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