Looking for some help with Noise/hot pixels

Hello all,

I was hoping I could get some help in figuring out what is going on here with my photos? I am very new to photography. I am trying to take some decent photos of the night sky, but they keep coming out very noisy and/or with hot pixels. I bought my Nikon D3100 used at the beginning of july , but it only had about 2500 actuation's on it. I know that with this beginner camera I should not expect results like a pro, but the photos are very grainy and seem to have a lot of hot pixels. I have read to take care of this problem in post processing but I seem to have trouble doing this. I downloaded a hot pixel mapping program for post processing but it does not seem to think I have hot pixels. I took a long exposure photo at a high iso with my lens cap on for this program to map the pixels, I will provide that photo so the results can be viewed and maybe some suggestions can be given. Thank you in advance for any assistance with this.

P.S. I just re read this post, and just to make it clear I am asking for help with determining whether or not if I have a bad hot pixel issue or bad noise issue.....................thank you again

here is the Exif from the raw photo
exif.make=Nikon;
exif.model=D3100;
exif.artist=;
exif.date_time=2014:08:06 01:46:18;
exif.date_time_original=2014:08:06 01:46:18;
exif.date_time_digitized=2014:08:06 01:46:18;
exif.exposure_time=25/1 sec;
exif.ISO_speed=ISO-1600;
exif.f_number=f/3.5;
exif.focal_length=18;
exif.color_space=1 (sRGB);

Welcome to the forum,sorry your not happy with your results but it shouldn't be because as you say its a beginners camera,its a very capable unit,what ISO are you normally shooting at and do you crop much.

I dont crop at all, and I am very aware that this is a wonderful camera and very capable, but as I have asked this question elsewhere I have been told by others not to expect much from a beginner camera, so i was trying to avoid useless information by saying I new it was a beginner camera, that way I might get help with noise/ hot pixel issue I have. I downloaded a program called hotpixelfixer which maps the hot pixels but it didnt seem to find any hot pixels. I have tried shooting at iso 1600 for 30, 25, and 15 seconds, and at iso 800 for the same amount of seconds and 400 for the same amount of seconds. here is an actual photo I took of the stars and here is the exif data for the photo...............................I am just looking for help with the best way to process this, and / or if I have an issue with hot pixels/noise

exif.make=Nikon;
exif.model=D3100;
exif.artist=;
exif.date_time=2014:08:04 23:17:17;
exif.date_time_original=2014:08:04 23:17:17;
exif.date_time_digitized=2014:08:04 23:17:17;
exif.exposure_time=15/1 sec;
exif.ISO_speed=ISO-200;
exif.f_number=f/3.5;
exif.focal_length=18;
exif.color_space=1 (sRGB);

I'm far from an expert but that looks like high ISO noise to me. I used to get noise like that on my Olympus cameras at higher ISOs

I was referring to the first photo you added, not the new one you added while I was typing

Looking at the settings you used for the image posted

ISO 1600 and a 25 sec exposure at f/3.5

I can't see any hot pixels but there is considerable noise which is not uncommon at these kind of settings.

I would keep the ISO below 800 if possible even lower. Also cover the eyepiece for the viewfinder as you do get light leaks from there.

Have you tried talking multiple shots at say 10 secs each at ISO 400 and then stacking them?

As Mike asks how much do you crop because you can reduce noise in down sizing the image.

You can also get software that reduces noise as well but that starts to up the cost

There are a couple settings you should examine on your D3100: Noise Reduction and Active D-Lighting. The first option you want enabled (it's disabled by default) and the other you want disabled (it's enabled by default) for this type of long exposure, night-photography. Both of these options are in the "Shooting" menu (camera icon) of your D3100.

Enabling the Noise Reduction feature will, somewhat obviously, help reduce noise so you want this option turned on. The second option, Active D-Lighting, attempts to balance high contrast scenes and does a good job but at the expense of increased noise in the shadows. You don't need this sort of correction, or added noise, when shooting at night so you want to make sure this option is turned off. For shooting in daylight you may want to re-enable this feature.

If you don't have a manual since you bought used, you can download the D3100 Reference Manual directly from Nikon. This manual is much more expansive than the smaller User Manual.

...

I don't see a hot pixel issue, just a lot of noise. I recommend you follow Horoscope Fish's advice.

Wow thank you very much for good and quick information, I am new to this so photo editing is something I am trying to figure out. I am trying to keep cost way down as money is tight right now, so I am looking at freeware photo editing/ post processing but I think I may have to spend a little money and buy a good all around post processing/ editing program. Any Suggestions on that, or point me in the right direction in the forum.

I am going to try the the suggestions and I will post a new photo tonight. Thanks again you guys, very helpful

blueridge142 said:

I am going to try the the suggestions and I will post a new photo tonight. Thanks again you guys, very helpful

Click to expand...

Sorry for all the edits on my previous post but it's early on the left coast (I'm an early-rise insomniac) and I'm a little groggy. I hope something in there helps. Your D3100 is a very capable camera but having good post-processing software is really the flip-side of digital photography regardless of your camera and an essential tool for this hobby. If you can swing it, you can get Photoshop and Lightroom from Adobe for $10 a month via their Creative Cloud Photography Bundle. If you're going to get into doing digital photography, that means you're going to be getting into doing post processing; so you might as well learn these applications now because most likely this is where you'll wind up eventually anyway.

Abobe Photography Bundle

....

I think this was discussed a week ago, still here goes.

To shoot night sky you need low noise, but long exposures increase the noise a lot, so does higher ISO. Here is a method used by Astromomers
. Use ISO 100
. Use your lense wide open
. Use a lot of 1 second or less exposures, taken one after another. Instead of 30 seconds at ISO 1600, which translates to around 30*16 = 480 sec at ISO 100, take 500 shots at 1 sec, one after another. Then merge them using software. The advantage is

. There will be less thermal noise in each shot.
. Minimum noise at ISO 100
. While merging the noise decreases as square root of number of shots

A Look at Reducing Noise in Photographs Using Median Blending
Sharp low-noise photography using multiple photos

Editing, I currently use Elements, which seems to be a cut down version of photoshop and lightroom. It does have a few limits, but after using it for more than 3 years, its only just becoming apparent to me what those limitations are.

Its not free, but I got my copy on a Black Friday sale, so it was dirt-cheap.

If you are looking for a no-cost software for image editing, the best is a free app called Paint.NET. It is good for touch-ups and has many of the features of older versions of Photoshop.

I used it for years with great results.

But I do have to admit that after getting Lightroom I am absolutely hooked. I recommend starting with Paint.Net so you will understand photo editing better (terminology, effects, noise reduction tools, etc) and then get Lightroom which really doesn't cost THAT much.

One further thought on the editing program is GIMP, that is free, but (to me) not that intuative... a friend of mine uses it for all their editing though.