ISO/NOISE question

[ewick]

I feel I should already know this but I don't i have found some good relate stuff but not the answer to my baffling question. I shot some images in low light. my camera is a d90 and I was using a 50mm 1.8 aperture. my settings were 2.8 and shutter speed 200 with off camera flash and an iso of 600 and I got noise. Today I shot with my 18-105 kit lens at 5.6 ss125 and iso 1250 and I got the same amount of noise. How do I get crisp images in low light with off camera flash. All I need is a starting point to go from. should I use the widest aperture possible with a hgh iso or keep my iso as low as i can. whats the point of the d90 having such high iso if you are going to get noise any ways? a little help would be greatly appreciated.

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[SCraig]

Noise is present in every shot you take. That's a fact of electronic life. In most properly exposed, relatively low ISO shots the signal to noise ratio, or the ratio of good signal to noise, is so high that the noise is not noticeable. In low light with high ISO and longer shutter speeds the SNR starts to get lower and noise becomes noticeable, most commonly in shadowed areas.

First, if you were shooting with flash did you really need ISO 600 or could you have gotten by with less?

Next, when shooting at higher ISO maximize the SNR by limiting the shadow areas. Do this by slightly overexposing the shot, just to the the point that no highlights are lost, and then reducing the exposure in post processing. See This Article.

[EDL]

Post some examples.

[BlairWright]

The amount of noise is directly associated with the ISO. Lower the ISO and the noise levels will improve, let your flash do the work.

[KmH]

Yep! Lower the ISO, turn up the flash power output, use the shift key.

[Mach0]

What are you shooting at 1/200 s?

[jake337]

The amount of noise is directly associated with the ISO. Lower the ISO and the noise levels will improve, let your flash do the work.

Yes but good lighting will let you use higher ISO setting with less noise. I forgot to lower my ISO when I turned on my flash for this one to grab a quick pic of this beetle.

D90 - 1/200 - F16 - ISO 3200

[Mach0]

Yes but good lighting will let you use higher ISO setting with less noise. I forgot to lower my ISO when I turned on my flash for this one to grab a quick pic of this beetle.

D90 - 1/200 - F16 - ISO 3200

X2. I was at a surprise 50th last night and shot with two off camera flashes at full power @ ISO 500. No noise. Of course it was dark as can be lOl.

[480sparky]

Noise is a direct result of ISO.

For example:





The boxed area is magnified in the following images:


ISO 100:






ISO 400:






ISO 1600:






ISO 6400:







ISO 25600:







Details of the above samples:

ISO 100:





ISO 400:






ISO 1600:






ISO 6400:






ISO 25600:

[jake337]

Well of course it is sparky, but take another shot at 25600 without good lighting or good exposure and compare it to a two shote at iso100 with good and bad lighting and I think the difference is pretty clear.

What I said was wrong. Your going to get more noise with a higher ISO settings but with good light it will be less noticeable.

[Garbz]

whats the point of the d90 having such high iso if you are going to get noise any ways?

Would you rather have the ability to take a noisy shot, or a camera that takes only the nicest of photos but doesn't work at all when it gets a bit too dark?

[gryphonslair99]

Photoshop plugins that can deal with noise issues in a photo = Dozens

Photoshop plugins that can salvage a photo from an exposure that recorded virtually no date, ie. black = 0

Which do you want?

[TCampbell]

There's always basically some noise -- the question is (a) to what extent and (b) can you notice it?

The higher the ISO, the more likely you are to notice it. The physical temperature of the sensor also contributes to noise -- hotter sensors produce more noise. Astrophotographers routinely take very long exposures, so the better cameras used for astrophotography have cooling systems built in to keep the temperatures low.

I tend to "notice" the noise more when I look in the dark tones of an image. For example... I've seen some moderately high ISO images of a bride & groom -- groom in black, bride in white -- and see all kinds of noise in his black tux, but not so much in her white dress. This is in the very same photo.

Some sensors might be more likely to have noise in certain colors, though I find the luminosity to be the greater contributing factor when I go through my own images.

The point of this is to that once you recognize what causes noise and when you're likely to have it, you'll be better at predicting when an image will have noise even before you take the shot, and what factors you might be able to control to reduce the noise. If the camera isn't moving and the subject isn't moving, then you can keep a shutter open as long as you need... in which case just drop the ISO to it's minimum setting. If you own a tripod (This is one of those things that I consider to be a "necessity". Every photographer should own a decent tripod.) then that's half the battle.

[Big Mike]

As mentioned, the higher the ISO, the more noise you get. But, as Tim points out, noise is more noticeable in darker areas of a digital photo. This is because the s/n (signal to noise) ratio is lower in the dark areas. In other words, there is less light, thus less information in darker areas, so the noise becomes more visible.
That is why some photographers prescribe to the 'Expose to the Right' theory. Expose Right

Also, did you do any post processing on the images? Specifically, did you brighten them? That is the worst thing you can do, when it comes to noise. Shooting an image that is too dark, gives you a low s/n ratio, and when you brighten it, you brighten the noise as well. But if you nail your exposure, or shoot it a bit brighter and then darken it, you will see much less noise in the end.

[The Barbarian]

Back in the stone age, when we collected images on strips of animal protein coated with silver emulsion, there was grain. Noise is digital grain, and the same trade-offs apply.