Night time photography

F

fluorescentsam

Senior Member
when i do long exposure on bulb mode on a night sky, i get these flecks. i am not sure i they are distant stars and light sources or noise. also there are these 3 smudges could that be lens problems? thanks (at 100% crop it is easier to see flecks)
DSC_0412.jpg
f/36 exposure 3096.7 seconds ISO-100
 
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shl3608

shl3608

Senior Member
the picture is difficult to see but immediately, but I'm drawn immediately to the EXIF data. Was this shot at f/36? You should try shooting wide open to see if the smudges are indeed on the lens itself. also, how long was the exposure?
 
Scott Murray

Scott Murray

Senior Member
Firstly why are you shooting at f/36? I would say that they are smudges but in reality you do not need to go above f/11 for night shots and even then wide open is normally best depending on your lens etc.
 
W

wornish

Senior Member
Shooting at f/36 will certainly show any small dust specks on the front of your lens, if you shoot wider you won't see them as others have said.
 
BackdoorArts

BackdoorArts

Senior Member
While I can't see specifically what you're speaking of, you have made an image where the shutter was activated for more than 51 minutes. If you read your manual you will see that after a certain period of time (far less than that) an active sensor can build up enough heat that you will get hot pixels and sensor noise. Nikon has installed hard stops on video features at 20-25 minutes to protect sensors from potential damage. Your shot is more than twice that length.

I'm not saying you damaged your sensor, but I am saying that you exposed it to potential damage from overheating. What you see is likely noise from an overheated sensor.

There are many tutorials on shooting things like star trails, which is what I'm assuming you were going for, all of which involve the merging of multiple shorter exposures at higher ISO and wider aperture. That's probably the way to go.
 
Marcel

Marcel

Happily retired
Staff member
Super Mod
wornish said:
Shooting at f/36 will certainly show any small dust specks on the front of your lens, if you shoot wider you won't see them as others have said.
Click to expand...

Dust on the front of the lens does not show on a picture. They would only make the picture softer or produce more flare if the shot was backlit. Dust on the sensor on the other end will show more if the lens aperture is smaller, usually from f11-22. The dust on the sensor is seen as a black or darker spot and can usually be seen more in the blue sky portion of the pictures or on an even colored surface.
 
M

Moab Man

Senior Member
I wouldn't try to guess what is going on until the technique is corrected. As the others said, f/36 is not good.

A 50 minute exposure? Why? What were you trying to capture?
 
Marcel

Marcel

Happily retired
Staff member
Super Mod
You need to find instruction to take night star pictures. Usually, you'd use iso 800 and the lens would be open to it's maximum aperture. I really don't understand why you'd want to use f-36 and iso 100. It seems very counter productive to me.
 
Scott Murray

Scott Murray

Senior Member
Here is a list of settings you would need to use at several common apertures to get a 30 second exposure:


f/1.4 and ISO400 = 30s
f/2.8 and ISO1600 = 30s
f/4.0 and ISO3200 = 30s
f/5.6 and ISO6400 = 30s


It goes without saying (but I’m going to say it anyways) you really want to try to get your hands on the fastest lens you can (largest aperture, smallest “F” number). These are just a good base to start with, once you frame your shot and take a few test shots, you will probably need to play around with the ISO to get the proper exposure.

Then you will need to start taking 30sec exposures over the next few hours to get star trails, this will require merging/stacking in PS etc.

Or if you would like only a single exposure try, f/4 ISO 100, 2 min.
 
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W

wornish

Senior Member
You are getting there, first one is best but still too long an exposure. Reduce to 25 sec exposure time and repeat the process 20 or more times without moving camera or changing anything else. Then stack shots using Starstax.
 
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