Grainy photos

[Womble_Lancs]

OK, a question for our seasoned photographers.

The other night, I went out to take some evening photographs at a reservoir near where I live. I left the camera set on 'auto' and was quite pleased with the look of the pictures on the camera screen. However, when I got them home, they were really grainy and, to be honest, rubbish. According to the info, the ISO setting is 1600. If I had set it to, say, 400 with a longer exposure, would they have been less grainy?

 

[scanker]

Yes. Looks a nice scene though.

 

[Womble_Lancs]

The picture in RAW is much brighter. Converting it to JPG has darkened it a lot.

 

[maddave]

The higher the ISO the more grainy it becomes. Keep your ISO low 400 or less with a longer exposure. Also Wayland does a lot of IR shots that take long exposures and informed me that DSLRS sensors heat up over long exposures too which can increase noise, it's getting the balance right but the lowest Iso with a bigger apature and longer exposure seems to be the key

 

[Womble_Lancs]

I was using a tripod and remote shutter release, so I could have done a much longer exposure, given that there were no moving objects in the frame.

Doh!

I'd left it on automatic ISO, because, well, I'm lazy. I reset it to 400 last night.

 

[maddave]

I was using a tripod and remote shutter release, so I could have done a much longer exposure, given that there were no moving objects in the frame.

Doh!

I'd left it on automatic ISO, because, well, I'm lazy. I reset it to 400 last night.

Like me the other week. Went out on a lovely summer day, took 1000+ pics and when I got in my white balance was set to tungsten light.. Result 1000+ blue hued photos, wasted day

 

[hedgepig]

Lower ISOs do indeed produce less noise and given the chance to shoot the scene again you should use the lowest ISO possible for the aperture and shutter speed settings that you need. However, underexposure is also a major cause of noise. This is because of "bit depth" - I'm not going to get into a technical explanation of this here but in practical terms you should review your histogram and ensure that as much of the histogram is to the right as possible without your highlights blowing out.

Try it and you will see what I mean - shoot the same scene twice slightly underexposing one and getting the other as close to the right as you can (without blowing the highlights). After converting, look at the shadow areas - you will notice considerably more noise in the underexposed image. The image you posted does not have any areas of bright highlight and it looks underexposed to me.

The noise caused by too high an ISO and by underexposing are different in appearance and are known as chromatic noise and luminance noise respectively. Chromatic noise looks like lots of little coloured specks, luminance noise appears as blocky areas of lost detail. I suspect that the noise you are referring to is chromatic noise and is caused by high ISO (1600 is high!), but you might also want to check for luminance noise.

What were your shutter speed and aperture?

 

[Womble_Lancs]

Like me the other week. Went out on a lovely summer day, took 1000+ pics and when I got in my white balance was set to tungsten light.. Result 1000+ blue hued photos, wasted day

You could always use the 'remove colour cast' tool in photoshop?

 

[hedgepig]

Like me the other week. Went out on a lovely summer day, took 1000+ pics and when I got in my white balance was set to tungsten light.. Result 1000+ blue hued photos, wasted day

Shoot RAW and you will never have this problem again

 

[Womble_Lancs]

The image you posted does not have any areas of bright highlight and it looks underexposed to me.

Unfortunately, the conversion to JPG has made it a lot darker than the original - you can see the noise much more on the original version.

What were your shutter speed and aperture?

Shutter speed - 0.50 sec.
Aperture - f/4.00
ISO - 1600

 

[hedgepig]

Right, with that kind of scene and using a tripod your settings should have looked more like:

Shutter Speed: 30s
Aperture: f/11
Iso: 200

 

[Womble_Lancs]

Blimey, that's a huge difference. If I get another decent evening, I'll go out and have another try. 30s is a long time (!)

Why f/11? I thought that a larger aperture would let in more light?

 

[scanker]

I think that's to increase the depth of field, but I'm a rank amateur compared to the other posters in this thread. I'm watching with interest though - I bought my first dSLR yesterday!

Can't you make the image as light or as dark as you like from the raw image, or have I got the wrong end of the raw stick?

 

[hedgepig]

Scanker is correct - it increases the depth of field and f/11 is actually a smaller aperture and lets less light through (as the number increases the aperture gets smaller). You should use this in conjunction with the hyperfocal distance to get maximum depth of field. Typically you can guess this by assuming the the hyperfocal distance is going to be about 1/3 of the distance in to the frame.

For example in this photograph the millstone in the foreground was only a couple of feet from the camera, but the whole of the frame is in focus - I can't remember the aperture setting off the top of my head but I know it would have been around f/13

In contrast, in this image the aperture is wide open - probably around f/2.8 - so that the background is intentionally thrown out of focus. Hope that helps and gives you an idea of how the aperture can be varied to give different results.

 

[Womble_Lancs]

Scanker is correct - it increases the depth of field and f/11 is actually a smaller aperture and lets less light through (as the number increases the aperture gets smaller).

Yes, that's what I meant - surely a larger aperture would let in more light than f/11.

My photos never seem to look as clear as yours. What resolution are they?

 

[hedgepig]

Yes, that's what I meant - surely a larger aperture would let in more light than f/11.

My photos never seem to look as clear as yours. What resolution are they?

Yes a larger aperture does let in more light but a larger aperture is denoted by a smaller number.

Check the picture here http://en.wikipedia.org/wiki/F-number and you will see what I mean. f/5.6 is a smaller aperture (hole) than f/4 and lets in half the amount of light.

As for the "sharpness" of the pictures - wow, big topic in itself, however, resolution (as measured by pixels) is actually not near the top of the list. I can give you a rundown of the various variables, but lets get the aperture thing sorted first.

 

[Womble_Lancs]

Yes a larger aperture does let in more light but a larger aperture is denoted by a smaller number.

Yes, I was trying to tell you that I know that already! I just worded my original comment poorly.

 

[hedgepig]

Oh right, I misunderstood. In that case I assume you mean, why would you choose and aperture that lets in less light?!?

 

[Womble_Lancs]

Yes, that's what I meant

I'm not a very experienced photographer and use the 'trial and error' method a fair bit.

 

[Womble_Lancs]

PS, just had a look at your website, some fantastic pics on there.