D70 problem

[ryankowall]

I've recently gotten into doing long-exposure night photography with my D70. I get these two washed out spots in the upper-left of the frame. It cant be flare because it's the exact same spots every shot in the same place. The longer the exposure, the bigger and brighter the spots get.

Any ideas?

[actionshot]

this is my first time posting. the purple fringing is amp glow. the only way to avoid it is to use in camera reduction or dark frame subtraction in photoshop.

[ryankowall]

hmm the camera reduction doesn't help at all. Could someone give a quick explanation of amp glow? I'm completely clueless as to what it is.

[bytethis]

G'day Ryan.

I also own a D70.

I do a lot of night photography. I'll put forward two ideas.

One is that you may have a dirty sensor...not dirty as in mud or crud, but dust specs. Unfortunately pretty much all DSLRs are prone to dust, often microscopic particles not visible to the naked eye, but will show up and specks when conditions suit...often this is when you wind back aperture to f18 or larger...at these apertures, ligfht can no longer 'bend' around the speck and you might as well have a boulder in there. Dust can enter the chamber by simply changing lenses...

The second (more than likely) explanation, would be light entering from behind the cam...don't forget that the SLR (film or digital) is 'through the lens'...if you in fact looked back though the lens, you can see back through the eyepiece.

So, if you were say, shooting a bridge at night, and behind/above you was a street lamp, if the exposure was long enough, e.g. 3-5 seconds, then light from the street lamp can 'leak' in through the eyepiece. This will bounce off the penta mirror straight onto the sensor (along with the image coming through the lens)

How do you stop this? Two ways. Either simply cover the viewfinder with your hand during exposure, or use the weeny little eyepiece slide/cover that came with your cam (this is exactly what this is designed for)

Hopefully it's the latter.

Incidentally, there's a 3rd phenomenon, called ghosting, and it's relevant only to digital cams (mainly SLRs) and it's where the light coming in to the lens bounces off the sensor and back onto the back of the lens and back onto the sensor again. I've not yet had this happen (good Nikon lenses) but is plausible in your case also.

Hi actionshot.

I'm not sure where purple fringing came into the question but that's chromatic aberration and comes with bright light sources and cheapy lenses. I've also shot for 21 years and never heard of amp glow. I'd love to know what this is also.

btw don't turn the NR off if you're doing long exposure night stuff...it reduces noise significantly. Also don't forget, that the NR program takes just as long as the exposure itself, so don't go jolting your cam during writing etc as it can corrupt the image (a 15 second exposure with NR on will ultimately take 30 seconds from capture to writing to the card)

Good luck and enjoy the D70.

[famjad21]

Here's my 2 cents:

If it's in the same spot every time, it sounds sensor related. Try a small bulb blower (don't use a brush unless it's specifically made for sensor cleaning) to clean off the sensor.

Frank

[ryankowall]

so i guess it is amp glow. Go to
www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/481815/Main/480997
and scroll down to the eight post. These are the exact same two spots on my pictures.

[eketelon]

See if this link helps. It talks about that very same thing.

www.kenrockwell.com/nikon/d200/d200-long.htm

Good luck and happy shooting.

[marluck]

I own D70s and last vacation I made some long expose pictures, and I was very sad when I discovered these pink spots. I asked NIKON USA and this is what they said:

Hello Mark,

This resembles a light leak, but that's not what causes this. This looks like a CCD that is generating a lot of heat from prolonged charging. You may notice that CCD cameras designed for telescopes have heat syncs on them, and some even have a cooling fan or a 'coolant' system, and this is the reason. Some telescope cameras use what's known as a Peltier coolant device to carry heat away from the sensor.

In your case, the amplifier in the sensor is cranked all the way up to an ISO of 1600, combined with an 8+ minute exposure and a very dark subject, and this is the result. You may want to lower the ISO way down to 400, and wait for the ambient temperature outside to drop more to around 40’…’‚‚ºF (no lower than 35’…’‚‚ºF) for space shots. Turn off the VIVID mode, and leave off the Noise Reduction (it erases stars).

Use the fastest (largest aperture) lens you have to limit the time needed to collect light. I notice from the shooting data, you have the Aperture set to f/22 for the shot with the most purple. Open that lens all the way up, you can do this in Manual mode.
Allowing the camera to cool down in between shots may help too. This is the best advice I give you for the best chance with this camera and technology, but keep in mind, it is not designed for that function.

There are many differences between CMOS and CCD sensors. CCDs are more costly to produce, but generally produce a much better image. CCDs use more power than CMOS sensors and as a result, will generate less heat. This is why you may not have this problem at this scale with a CMOS camera.


I hope this helps,

Dave

Thanks for using Nikon products!