Hot Pixels?

Dogdots

Today when I was taking some photos I noticed "hot spots" or what I think are hot pixels. Only what really has me perplexed is they are in different areas and only in certain photos. All the photos I took in this series had them tho.

If someone could explain this I would love it. I've attached 2 photos taken. They were taken in sequence, but the spots are in different spots. Never have had this happen before to me. I was using my 40D with the 70-200 2.8 lens.

1 -- There are 2 of them in this one...forgot to circle the one on the pant leg.




2 -- The next photo I took right after the one above.

Allen

I noticed this a few months back also on 7D, many little white specks, different locations on every photo.
I originally thought they were very small droplets with sun glint picked up by the enormous resolution.

Dogdots

Allen wrote: »

I noticed this a few months back also on 7D, many little white specks, different locations on every photo.
I originally thought they were very small droplets with sun glint picked up by the enormous resolution.

Never thought about small droplets with sun on them. It's something weird tho...never seen it before.

Richard

I noticed something similar a while back. They wouldn't always appear and they were in different places in different shots. I finally realized that some very big trees were shedding stuff into the air and the sunlight made it very bright. .

cab.in.boston

I have noticed hot pixels on both my D90 and D300. In both cases, they were in the same place every frame, and either bright red or blue, with bleed-over onto the surrounding areas. The first one I found on my D90 was red and right near the middle of the frame. If you shot a person correctly, it looked like a nice zit. Blech.

Anyway, Nikon repaired them, but since I've been using Lightroom, it automatically finds and removes hot pixels, so I haven't seen any in quite a long time. From what I understand, they're very common.

Dogdots

Richard wrote: »

I noticed something similar a while back. They wouldn't always appear and they were in different places in different shots. I finally realized that some very big trees were shedding stuff into the air and the sunlight made it very bright. .

So I can blame it on the trees

You might be right .. both of you. There is so many different things in the air we can't see. First I thought it was sunlight catching on the dog spit

Dogdots

cab.in.boston wrote: »

I have noticed hot pixels on both my D90 and D300. In both cases, they were in the same place every frame, and either bright red or blue, with bleed-over onto the surrounding areas. The first one I found on my D90 was red and right near the middle of the frame. If you shot a person correctly, it looked like a nice zit. Blech.

Anyway, Nikon repaired them, but since I've been using Lightroom, it automatically finds and removes hot pixels, so I haven't seen any in quite a long time. From what I understand, they're very common.

I don't have Lightroom so I'll have to clone these buggers out.

Love your avatar -- beautiful Bernese Mt. Dog

cab.in.boston

Dogdots wrote: »

Love your avatar -- beautiful Bernese Mt. Dog

Molly says thank you. She thinks she's beautiful, too.

Dogdots

Molly looks like a pup still

basflt

Dogdots wrote: »

I don't have Lightroom so I'll have to clone these buggers out.

nothing is automatic
the same tool is used in PS too ; spot healing brush
and that works more automatic than the spot removal tool in LR

cab.in.boston

Dogdots wrote: »

Molly looks like a pup still

Nope, she turned 5 in June. She is small, though, only about 70 lbs. She still acts like a pup sometimes, though. Her mom is about to turn 10, and other than her eye patches looking a bit faded, you'd never know it, b/c she acts like a 2 y/o.

Here are some pups we got to see over the weekend. They're from a litter Molly's half-sister had back in June. I LOVE puppy breath!



(Sorry to hijack the thread. I'll stop now. )

Dogdots

basflt wrote: »

nothing is automatic
the same tool is used in PS too ; spot healing brush
and that works more automatic than the spot removal tool in LR

I'll give that a try. A friend just emailed me a test to try. Tried it out and didn't see anything.

****- Set for a high resolution.
- Set ISO 100.
- Any lens
- Set for Manual Focus.
- Set Mode M, Any Speed, any Aperture.

- Take a picture with the lens' cap on
- Load this picture to your computer, open it with Photoshop or any graphic editing program (Paint, Corel...)
- The "photo" should be all black.
- Zoom in to enlarge the photo as much as posible.
- Use the rectangular select tool to select and check the selected area, the dead pixel should be any white dot, point.
- Delete the checked area and repeat select another area, check and delete piece by piece... until the photo is complete checked
- Remember to save from time to time.
- It takes about an hour to complete.

cab.in.boston

basflt wrote: »

nothing is automatic
the same tool is used in PS too ; spot healing brush
and that works more automatic than the spot removal tool in LR

From what I've read, Lightroom and ACR will automatically detect and remove hot pixels. All I can say from experience is that when viewing a RAW file in LR, I've never seen a hot pixel, even if they are visible when viewing the same image in another application (like the Nikon-bundled ViewNX or even the preview JPEG on the camera's LCD).

basflt

cab.in.boston wrote: »

From what I've read, Lightroom and ACR will automatically detect and remove hot pixels. All I can say from experience is that when viewing a RAW file in LR, I've never seen a hot pixel, even if they are visible when viewing the same image in another application (like the Nikon-bundled ViewNX or even the preview JPEG on the camera's LCD).

spots above aint hot pixels [ dont know what they are , though ]
my guess is dust , flying around in sensor compartment and light strikes it ?
but . they can easily be removed
with 2 or 3 clicks , in this case

cab.in.boston

basflt wrote: »

spots above aint hot pixels

I realize that. I had responded earlier with the intention of describing what a hot pixel was, that they would be in the same location shot to shot. I was basically reinforcing the idea that these are not hot pixels. Then I said that in LR true hot pixels are automatically mapped out of the image. You said that "nothing is automatic," so I was just restating that in my experience and from what I've read, hot pixel identification and remapping is indeed automatic. No worries.

basflt

cab.in.boston wrote: »

i realize that. I had responded earlier with the intention of describing what a hot pixel was, that they would be in the same location shot to shot. I was basically reinforcing the idea that these are not hot pixels. Then i said that in lr true hot pixels are automatically mapped out of the image. You said that "nothing is automatic," so i was just restating that in my experience and from what i've read, hot pixel identification and remapping is indeed automatic. No worries.

pixels are so small , one would hardly see them
IMO Mary's camera is ok
smiley_swinging.gif

Dogdots

Dust moving around in my sensor compartment -- that makes sense.

JimKarczewski

Hot Pixels also do not move, as exhibited by the original posters images. If they are consistently in the same place, then you MIGHT have a hot pixel, after dust/etc is ruled out. As mentioned, the best way is either a lens cap and exposure or even with a body cap on and no lens. If there are consistently "on" pixels, then you just send back to Canon/Nikon/etc to have them permanently mapped out of the image sensor.

cab.in.boston

basflt wrote: »

pixels are so small , one would hardly see them

Indeed, at full resolution they are not very visible. But if you zoom in at all, perhaps to check focus, you will see them. You don't need to get all the way to 100% or larger, either, before they start showing up. It's not just the one pixel that will be affected, as the demosaicing uses surrounding pictures to generate color. If for example, you have a stuck red pixel, then the processor thinks that that location has a full red value, and the surrounding pixels will have more red in them than they should. Here is a 100% crop from when I had a stuck pixel on my D90. This shot was of a plain beige wall:



That red spot was on every photo, and it was in the same spot every time. If I made a full size JPEG, you could see a little blemish.

I guess there is a difference between a "stuck" pixel and a "hot" pixel. Stuck ones are just faulty and read full value every time, no matter what. Hot pixels tend to saturate during long exposures and therefore may or may not be present in every image or always at the same location.

IMO Mary's camera is ok
smiley_swinging.gif

I agree. I don't think this is a hot or stuck pixel problem.

Mav

cab.in.boston wrote: »

I have noticed hot pixels on both my D90 and D300. In both cases, they were in the same place every frame, and either bright red or blue, with bleed-over onto the surrounding areas. The first one I found on my D90 was red and right near the middle of the frame. If you shot a person correctly, it looked like a nice zit. Blech.

Anyway, Nikon repaired them, but since I've been using Lightroom, it automatically finds and removes hot pixels, so I haven't seen any in quite a long time. From what I understand, they're very common.

From reading your posts, I'm pretty sure I have stuck pixels too... When you say Nikon repaired your camera, you sent it back or took it to the store where you bought it? Also, is it expensive?

Finally, does this automatic/semi manual fixing in LR or PS fix these as well?

cab.in.boston

Mav wrote: »

From reading your posts, I'm pretty sure I have stuck pixels too... When you say Nikon repaired your camera, you sent it back or took it to the store where you bought it? Also, is it expensive?

Finally, does this automatic/semi manual fixing in LR or PS fix these as well?

With my D90, I sent it back to the repair facility in New Jersey under warranty, all it cost me was shipping. When I got my D300 used, I noticed a couple of stuck pixels as well. It was out of warranty, but I wanted Nikon to do a general cleaning/service since it was used when I bought it. The service they performed, per the invoice, was called "Clean & Check, Sensor cleaned/calibration/hot pixel." The bill was $84.18 which included return shipping, so it was probably a little under $100 including shipping/insurance both ways.

As I understand it, LR (and apparently Adobe Camera Raw) automatically detects when a pixel is stuck and throws it away when it renders images. It does not "fix" the problem that exists in your camera, it just ignores the stuck pixel when it reads in a file. Obviously there are algorithms that tell it if a single pixel in a certain radius is maxed out but its neighbors aren't, then it should be ignored. So for all I know, my camera(s) still has stuck/hot pixels, I'm just not seeing them when I work in LR.

basflt

mayby this is usefull to anyone

http://www.starzen.com/imaging/deadpixeltest.htm

NeilL

basflt wrote: »

mayby this is usefull to anyone

http://www.starzen.com/imaging/deadpixeltest.htm

How to use this, please, Bas?

Neil

basflt

NeilL wrote: »

How to use this, please, Bas?

Neil

place your lens-cap on lens and block viewfinder w thumb
make some pics at different [low] speeds
save em to pc as TIFF
run the EXE
click browse and surf to the TIFF
click test

#

both my camera's had none
i not tried my P&S yet

NeilL

basflt wrote: »

place your lens-cap on lens and block viewfinder w thumb
make some pics at different [low] speeds
save em to pc as TIFF
run the EXE
click browse and surf to the TIFF
click test

#

both my camera's had none
i not tried my P&S yet

Thanks, mate!

Neil