Probably a really dumb question...

baby and crumble

... But what's the story with ISO? I mean, I know roughly what it is (I think) but anything I read seems to contradict itself, especially when it comes to ISO recommendations for shooting at night time in cities...

So really, what do people on here do about ISO? Do you adjust it, let the camera take care of it, or what?

I'm sorry if it's a silly question that's been asked before but I've tried finding out, and I can't figure it out at all at all!

Zo

Paulw

Do you know what ISO is? It goes back to film days, and the sensitivity to light.

For daytime, I'll use as low an ISO as I have to to get a decent shutter speed. So, in good light - ISO 100-200.

For shooting sport at night, under lights, I'll use ISO 800, 1600 or higher, depending on what I need.

The higher the ISO, the more noise will be in your images. It will also depend on your camera. Some deal with high ISO better than others.

There would be very very few situations where I'd let the camera pick the ISO to use.

Fajitas!

ISO goes back to film, it's a scale of how sensitive the emulsion is to light, and in digital terms, how sensitive your sensor is to light.

If you're shooting in low light, you can pop up your ISO to get faster shutter speeds, but you'll increase the grain or noise in the photo - Similarly, if there's quite a lot of light, you can reduce your ISO to reduce noise/grain and hopefully not overexpose by too much - it's something to play about with, and very handy if you can get to grips with using it manually

baby and crumble

ok, so low ISO (100-200 kinda region) is generally for good light, to be able to use a fast shutter speed, yes?

But in low light or at night and you want a fast shutter speed, you'd put the ISO up to a higher value, am I right?

quickdraw2

http://en.wikipedia.org/wiki/ISO_5800

a guide to ISO

pixbyjohn

Zoegh, try this experiment and maybe it will show you how ISO works, Set your camera to Aperture priority AV on Canon A on Nikon, now set your ISO to 100 and aperture to f4, take photo and see what your shutter speed setting was. For second shot only change ISO setting to 800, now see what shutter speed is for this shot.
The shutter speed will be faster for second shot.

Paulw

zoegh wrote: »

ok, so low ISO (100-200 kinda region) is generally for good light, to be able to use a fast shutter speed, yes?

But in low light or at night and you want a fast shutter speed, you'd put the ISO up to a higher value, am I right?

Yeah, fairly much so.

Give it a try and see. Trial and error.

stunt_penguin

As a better test you should set the camera up looking at, say, a table lamp that's turned on.. Set your ISO to 400 or so. Now, go to manual mode, set up a nice arpeture and shutter speed to nicely expose the lamp, and shoot that for reference

Now, without touching anything shoot the scene again with the ISO at 800, 1600 and beyond. You'll see that the scene gets brighter and brighter. Snap down to 400, 200, 100 and 50 (if you have 50) and you'll see the scene getting darker. When you download the images notice that at 100 the scene will be dark but have very little noise. The scenes at 800 and 1600 will, despite their brightness have lots of noise and look very grainy.

This demonstrates your tradeoff between ISO and brightness. If you're in dark conditions you might need a high ISO to capture the scene with an acceptable shutter speed. In bright conditions (sunlight) you rarely need the extra sensitivity so it makes sense just to drop to ISO 100 or so.

Hope this helps.

ThOnda

Get a loan or buy quickly highly recommended book "Understanding Exposure". It explains ISO on two or three pages using not butterflies :-) but bees. And it is really easy to understand, even my mother got it
The book explains basics that you really should know if you are at least a bit interested in photography.

baby and crumble

Ok, thanks guy, this makes more sense to me now!



Zo

CabanSail

Understanding how ISO works, along with Shutter Speed & Aperture, will help you to make decisions on how the exposure will change how your image will appear.

If you are trying to shoot hand held in low light then putting the ISO up high may be the best idea you can get higher shutter speeds, at the cost of more noise. However if you were shooting at night with a tripod and wanted to get Long Exposure photographs you would then put the ISO on to a low setting.

pullandbang

The other issue is with low ISO (100) and shooting at night, you will get noise in the shadows with the subsequent long exposures. You could push your ISO to say 400 or 800 to reduce your shutter speed and hence reduce the shadow noise. The resulting image will be fine except for maybe large prints.

As ThOnda mentioned, get your hands on Bryan Peterson's book, Understanding Exposure - it's a must!