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08-21-2010, 02:06 PM   #1
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K-7 Night Lightning Shot. Normal amount of noise/banding?

This image was shot on a K-7 with the standard DA 18-55 kit lens @23mm f/5.6 10s 100iso. I had been shooting many images back to back and i have heard this causes sensor heat buildup which can lead to the banding, but are the intensely blown out pixels also normal?

shopped all the dots out for the final version and it looks pretty decent at about 4x6 but wont go much larger than that thanks to excessive noise. to really see the pixels i am referring to need to click the image for the original size...they are scattered uniformly through out the entire frame...



08-21-2010, 02:15 PM   #2
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That's definitely not normal for ISO 100 - if this were taken at 6400, then it'd be another story.

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08-21-2010, 02:22 PM   #3
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oops i forgot to mention, this is pushed up 2 stops worth in my raw editor...would that make the difference?

if not, what would be the correct course of action here? advice greatly appreciated!
08-21-2010, 02:28 PM   #4
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You should have done pixel mapping before shooting, would have eliminated lot of hot pixels.
As far as banding goes, that might be normal, image did not expose well due to either using ISO 100 or because the lightning was good distance off, or the combination of both.

Cheers, Mike.

08-21-2010, 02:32 PM   #5
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QuoteOriginally posted by mboehm Quote
oops i forgot to mention, this is pushed up 2 stops worth in my raw editor...would that make the difference?

if not, what would be the correct course of action here? advice greatly appreciated!
Heck yeah, pushing will bring out nastiness.
Getting a nicely exposed lightning shot is pure luck.
I normally use ISO 200 f 5.6 and shoot jpeg, i am lazy
.http://www.flickr.com/photos/k_koskelainen/3519700814/

Last edited by Ex Finn.; 08-21-2010 at 02:43 PM. Reason: added flicker link
08-21-2010, 02:50 PM   #6
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Can someone elaborate on the causes of the hot pixels and how pixel mapping corrects them?
08-21-2010, 03:07 PM   #7
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Cause = semiconductor breakdown.

Camera will map the sensor, detect failed pixels and use averaged information from surrounding pixels to come up with imaginary value for the bad pixel, ie. smooth it out. If that makes any sense.

Cheers, Mike.
08-21-2010, 04:38 PM   #8
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I have had some that came out worse.

Operating near the heat limitation (104) causes really nasty banding and a ton of hot pixels.

I had one night at only 85 degrees and had probably 25-30 hot pixels and banding worse than your photo. I used pixel map but still had probably 5 hot pixels so I just gave up on night shots until the weather cools off.

The pixels go away if I test it in an air conditioned room and the camera has cooled. The k7 is not a fan of heat for sure. Also I have had the camera overheat when it gets up around 100 and attempting to use live view or movie mode.



Below picture (dark) was with the lens cap on to show pixels, those are not stars!

All ISO settings showed the same hot pixels. This only has happened in hot weather (unfortunately summer in Afghanistan)

Attached Images
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PENTAX K-7  Photo 

Last edited by LeeRunge; 08-21-2010 at 04:43 PM.
08-21-2010, 04:43 PM   #9
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QuoteOriginally posted by Adam Quote
That's definitely not normal for ISO 100 - if this were taken at 6400, then it'd be another story.
Considering were looking at a 10/1 plus +2 eV push, I think this is quite normal under the circumstances.
Having said that, the image cleans-up quite with a little NR and debanding, so it's all good from what I can see.

Last edited by JohnBee; 08-21-2010 at 04:48 PM.
08-21-2010, 04:56 PM   #10
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QuoteOriginally posted by LeeRunge Quote
Operating near the heat limitation (104) causes really nasty banding and a ton of hot pixels.

I had one night at only 85 degrees and had probably 25-30 hot pixels and banding worse than your photo. I used pixel map but still had probably 5 hot pixels so I just gave up on night shots until the weather cools off.
I'm not sure that this is only happens on warm nights. I took this shot of Dofasco on a morning where it was about 2-5 deg C with my K20D and I still saw some issues. Although, I admit that it wasn't as bad as you're seeing. Although in this case I solved my problem by cropping. Easier in this case than some of the previous examples.


Last edited by Simian Summit; 08-21-2010 at 05:08 PM.
08-21-2010, 04:57 PM   #11
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Two things cause noise: high ISO, and long shutter speeds. ISO 100 pushed two stops is the equivalent of 400, which is high-ish, but with a "normal" shutter speed, wouldn't have been too bad. Combined with a 10s shutter, though, and that's about normal for any camera on that type of scene (noise tends to be more visible in skies than other subjects).
08-21-2010, 04:58 PM   #12
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I'm curious as to how hot is was out when you took your lightning shot.

This is the first camera I have owned that ever exhibited a heat issue. One of the guys I work with shoots a T2i and it shows none of this at the same temperatures. (you can still pull out noise if you push ev)


Honestly this is the first camera I have seen hot pixels in ever. Previously if someone said "hot pixel" I would think pc monitor.


I love the K7's design but the sensor seems to be a pretty large weak point after dark or in hot weather. I was shooting my canon p/s with the same exposure time and it showed none of this, nor has it ever. It has also never shut down for heat in the same operating conditions.


I'm curious if others have had any of these symptoms with other brands, aside from noise as all cameras have that to varying degrees.
08-21-2010, 05:44 PM   #13
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My K-100D with 6MP sensor had / has hot pixels also. Same thing with some of our Panasonic security CCTV cameras at work, not so much with Pelco. They all are CCD.
I am from old school = complimentary-metal-oxide-semiconductor= garbage and low budget.
And I like my K-7 a lot.
08-21-2010, 09:00 PM   #14
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QuoteOriginally posted by mboehm Quote
oops i forgot to mention, this is pushed up 2 stops worth in my raw editor...would that make the difference?

if not, what would be the correct course of action here? advice greatly appreciated!
"pushing" a digital image is one of the best ways that I know of to increase the image noise & banding.

You could make the image look even worse by pushing another stop or two.

So the leason here is that under-exposing, and then pushing is bad.

Interestinly, over-exposing and pulling, is good.

Read up on "expose to the right". Do a google search.
08-22-2010, 06:28 AM   #15
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I tried to use Movie mode today in 95 degree weather (camera in shade) and it overheated again making it not usable for video in hot weather.

Regular pictures are ok but live view/movies shutdown with a red thermometer on the upper left appearing.


I would not recommend this camera if video was important and you live in a climate that gets hot. I suspect the sensor is more heat susceptible than most.
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