Interval timer STRANGENESS

Hi!

I've started experimenting with star trails and time-lapse photography using the D600's interval timer shooting functions, and I've had some real strangeness happening...

The first time I did it, I set a manual exposure, set it on 1 shot every 5 minutes, 999 photos total, and let 'er rip. It happily shot for a while, but when I downloaded the photos, they were gradually getting progressively and mysteriously darker...

It was a bit cold, so I thought it might be a power issue, so I bought the EP-5B power adapter.

This morning same setup, but: no cold, no battery, same result - a gradual darkening of all photos. The meta data in each picture says they were all shot with the same exposure though. I'm stumped.

Any one have any idea what might be going on?

Thanks!

BTW mods: I couldn't find an interval or time-lapse category in the forum. Might be nice!

So that I'm not confused, the metadata for each and every image is exactly the same, right? But over time the images get progressively darker, something verified also by the histogram shifting to the left? If so, this is an interesting puzzle.

And yes, a time-lapse category is a good idea. We should talk to Jdeg and see how busy he is.

Just curious, was the moon present and could it have been waning? Ambient light slowly getting reduced? Did you start after full sunset?

Like Dave, I'd need more information to help suss out the problem, like exposure times and maybe some shots from 30 minute intervals across the 5 hours. If nothing in the sky really changes then I'm stumped as to why it would change provided the exposure settings were the same each time.

Quick question, the histogram also confirms the dark change?

Also, shutter speed does not change either?

Yup, the histogram at the beginning was quite evenly distributed, at the end it was pushed out to the left. But the metadata shows exactly the same shutter speed & f-stop on all pictures.

OK, so you're in full sunlight? I would think it would have the opposite effect, but do you have the viewfinder covered, and if not is there a chance that light is slowly moving towards the back of the camera and compromising the photo by leaking through the viewfinder?

Good idea, but the camera was in full shade, both times this happened.

mattbalara said:

Yup, all the details are such that it is indeed a bizarre mystery.

– Full sunlight, no drastic light changes
– Visually the pictures get darker gradually, no sudden steps, just darker and darker as they progressed
– All exposures at 1600/f16
– All metadata in all images exactly the same, except the time when they were shot

It could be some weird combination of settings I don't remember setting, but I can't imagine what...​

Click to expand...

f/16 at 1/1600 in bright sun seems weird in itself. That would imply ISO 1600. What was the need?

Was Auto ISO on? Was ISO always the same? Auto ISO can still vary the exposure, even for (especially for) manual camera settings.

Nope, Auto ISO off. All shots were 1/1600 f16, 100 ISO.

But that gives me an idea. The lens I used, Nikkor 17-35mm 1:2.8D ED, seems to be much more light sensitive than it should somehow. The same exposure settings using it get a much darker picture using other lenses. Maybe I should have it checked…

But it still doesn't really explain why the series would get progressively darker…

Wow, this is a real head scratcher. There is nothing I can think of that would explain such behavior. Have you contacted Nikon yet? I'm curious what, if anything, then can offer as to a reason.

Nope, just happened this morning. I'll keep trying to figure it out myself, and if nothing else helps I'll see what Nikon has to say. Thanks for scratching your head with me!

mattbalara said:

Nope, Auto ISO off. All shots were 1/1600 f16, 100 ISO.

But that gives me an idea. The lens I used, Nikkor 17-35mm 1:2.8D ED, seems to be much more light sensitive than it should somehow. The same exposure settings using it get a much darker picture using other lenses. Maybe I should have it checked…

But it still doesn't really explain why the series would get progressively darker…

Click to expand...

Something is not right, because for many decades, Sunny 16 says ISO 100 is 1/100 second at f/16 in bright sun.

You should be underexposed four stops. Maybe the lens is not able to be stopped down for the exposure? But maybe creeping a bit with more tries? I doubt it is the timer. Maybe you should try to repeat this effect with a better working lens?

It would be very interesting to see one of those pictures (ISO 100, f/16, 1/1600 sec, in bright sun). It sounds very impossible.

I agree. As I said before, it would be great to see a sequence of a couple pics from across the timelapse with full EXIF.

Yup, I'm running a test right now with another lens. We'll see what happens...

And here are 3 pictures: the first, middle and last. EXIF should be in them so if you want to have a look, please feel free!

Looking at them separated from the sequence now, it's obviously clear that the change wasn't so gradual. It darkened mostly across the first third of the images, and after that got a little darker, but only slowly.

I'm going to go out on a limb and say this camera has problems. Any chance it's still under Nikon's warranty?

Hrm, not sure, but it's almost certainly not under warranty where I live, since I bought it in Hong Kong.

Do you suppose it's a function of leaving the camera turned on for a period of time? For instance, if you took shot A at 11 o'clock and then came back and focused on a different subject an hour later and the same an hour later than that, would you see the same darkening? Or do you think it's solely a function of the timed exposure and that refocusing it would snap whatever it is back to full sensor recording?

It's almost as if the attenuation of the sensor decreases the longer the camera is on. Or perhaps the light sensitivity is being decreased with time. Neither of which makes any sense.

I'd say it's time to visit an authorized Nikon repair shop and/or call Nikon directly and arrange to send them this series of images (I think they'll need the NEF's) and see what they can come up with.

Btw, you are shooting these in RAW format, right?

mattbalara said:

And here are 3 pictures: the first, middle and last. EXIF should be in them so if you want to have a look, please feel free!

Looking at them separated from the sequence now, it's obviously clear that the change wasn't so gradual. It darkened mostly across the first third of the images, and after that got a little darker, but only slowly.

Click to expand...

The problem is the first image. Even with -2/3 EV compensation, the shutter speed is simply unimaginable for ISO 100 f/16 in bright sun.

So the problem is NOT so much that the later exposures improve (1/1600 sec SHOULD BE UNDEREXPOSED), but is that the first one is so bad.