Long exposures and overheated pixels…
I just got wind of a long exposure issue from friend, Glen Gilchrist. Glen posted about losing a day of long exposure work because of numerous hot specs. These specs, looking like anything from a consistent bright pixel in every image in night photography to small white specs in images shot in daylight.
Here’s the folly pier in Charleston, SC at about 1030 am on a bright blue sky day. Using 15 stops of neutral density, I was able to get up to a 4 minute exposure in very bright sunlight. Although, everything looks ok in the lead image, here’s a magnified section with the overheated pixels more apparent:
Even when using an infrared filter (Singh Ray iRay) on a color camera, the resulting 4 minute exposure in very bright Florida summer sun recording moving clouds looks interesting:
but, upon closer inspection:
These white specs are all over the sky and took a while to clone out for a clean black sky.
These two examples were both 4 minute exposures in very bright sunlight, resulting in bright spots resulting from over heated sensors.
This is a known issue and one only need to search online under “long exposures and hot pixels” and read the many information links.
However, what about long exposures in bright diffused light??
Here’s one from Poverty Beach in Cape May, NJ: 4 minute exposure
And upon close inspection at 200% magnification:
no burnt pixels!
So it appears that long exposures in bright light is the culprit and there’s an unattractive fix: Turn on long exposure noise reduction.
This will help tone down to possibly eliminate the burnt out pixels at the cost of doubling the exposure time. After a 4 minute exposure, there is a 4 minute write time. One could miss a lot during the write time! However, if you are working close to the car, set up a second tripod (if you have one) so that you can continue to work while the processing is taking place on the long exposure camera.
So, is there anything we can do to remap the hot pixels?
I found this online from an anonymous Canadian photographer and will be giving it a run through in Cape May next week on my D3X:
This worked for me on a D300 and had 3 hot pixels. I set the menu to give me immediate access to the sensor cleaning, than placed the camera in BULB mode, pushed down the shutter for at least 20 seconds, then as soon as I released the shutter immediately went into sensor cleaning mode twice in a row. Strangely enough, this mapped out the dead pixels…they were flat gone and not seen again. It’s worth a try.
Trick #2: (This is the one that worked for me with both a D300 and a D700):
I had two hot pixels on my D300 last week. I did a sensor clean. Then set the camera to ISO6400 and with the lens cap on, took three
10 second exposure photos. The hot pixels disappeared!!! Much quicker and cheaper option than sending back to Nikon.
Not all of my hot pixels disappeared, but the vast majority did.
Source (where you can read about people’s results): D700 Hot Pixels? Help! – FM Forums
Any feedback on this would be really great to pass on to anyone with the hot pixel issue.
Thanks for taking the time and we’ll see ya online from Cape May!
p.s. oh yeah, don’t forget to check HERE for software/hardware discounts