Pictures taken with my 1D Mark IV show a blue horizontal line at the bottom from ISO 400 onwards.

[numenius]

Pictures taken with my 1D Mark IV show a blue horizontal line at the bottom from ISO 400 onwards. So far nobody has been able tot tell me the cause of this problem. The body is still quite new (15000 pics taken).

[ebiggs1]

You did try new CF and SD cards?  If you did, join CPS.  

[diverhank]

If the line is not removed by turning off the high ISO filtering then there's not much you can do at this point. This kind of line, I think, is caused by a few hot pixels in the sensor but is made into a straight line by camera processing and it will show up in the RAW file.
There is a freeware out there called Pixel Fixer that you can use to get rid of the line. The beauty is you can specify the ISO range to do the processing.
http://www.pixelfixer.org/


I haven't tried the above program or this one idea I have because luckily I don't have this problem...the 1DMk4, as with many others if not all, has the ability for you to map out the dirt...even though at this magnification it's hard to tell the offending pixels (brighter, larger than the rest), you might want to map them out. This alone might get rid of the entire line...it's worth a try.

Best of luck and sorry for your trouble.

[numenius]

i did.

[Ed1715]

I sure with I had found this thread a day earlier.  On 01-31-14 I noticed a similar problem with my MK IV.  I eliminated the memory cards as the problem.  I spoke with a Canon representative at CPS and decided to send it in for evaluation/repair.  They'll get a look at it tomorrow.  If it's a sensor issue and needs replacing the dollar amount could be north of $1000.  I certainly would have given these suggestions a try first.  I've included a photo with the green line I noticed.  I've had the camera since it was released and have 53000 shutter actuations.

The line is above the door knobs and traverses the entire photo.

.

[rfdesigner]

Just got back to the site:

If you've got it fixed then great.  Otherwise

Re your raw image you posted

Sadly the image you posted isn't RAW..  it's a JPEG, perhaps a JPEG of a RAW, but that doesn't help sadly, I'm after the .CR2 file..  any old picture from the camera will do, nothing with any 'artisitc worth'.

What I'm trying to do is pixel peep pre-debayering.  most packages don't let you do that (Even DPP doesn't) but one I use can.

[numenius]

https://www.dropbox.com/s/4onjchalabddhx0/CX7P2709.CR2

This time it should work!

[rfdesigner]

Here is what the end of the blue line looks like on the RAW image.  (it's a grey chequerboard as colour in a bayer matrix image is implicit by pixel location..   and this hasn't yet been 'interpreted')

https://www.dropbox.com/s/ahzuir3tuwis94d/blue_line.bmp

What we can see is the end of the line, and some 'slices' of both the dark and light lines, and a normal slice..  all slices are of the end of the lines, so the little graphs show a 'normal' segment on their leftmost edge, they are showing intensity vs position across the vertical branch in the image.

What these are telling us is that two rows are affected, one is overly dark and one overly light. this looks like a failure at one pixel location (the end of the line) damaging the entire row.  You should be able to see in the middle and bottom graphs that there is still real signal in both the dark and the light rows, so the right software and some reference flat-light and dark images might well correct for it...   alternatively the entire row can be scrapped and replaced with an average of the row above and below.

It's also safe to say your sensor isn't going to get better, but neither is it about to completly die on you..   my astro camera which is much more delicate as it's CCD has a couple of slightly 'hot' columns and I can process them out entirely.

I hope this is of some use.  (I tried processing out the column in IRIS but haven't found a sufficiently good way as yet.)

Derek

edit:  this of any use?..  (need a MAC)  http://people.csail.mit.edu/ericchan/tmp/FixBadPixels.pdf

[numenius]

Your answer certainly is of some use. Thanks for all your trouble and time you put into it. Next step will be to find the right  software. I'll begin with pixelfixer.