Auto ISO on D200

[py6km]

Can someone explain to me what this is, and why it's good please

I'm being a complete noob - I googled an article, but it still makes virtually no sense to me.

 

[PaulBoy]

Can someone explain to me what this is, and why it's good please

I'm being a complete noob - I googled an article, but it still makes virtually no sense to me.

As I understood it if you set Auto ISO to ON the D200 will always adjust the ISO for you automatically so that in poor lighting conditions it will increase the ISO to whatever you have told it is your desired upper limit (1600 or whatever) so that you always get an image albeit (if the ISO is very high) a noisy one!
Ken Rockwell swears by Auto ISO (do a search on his web site) KR can talk sense or total bollards so take his ideas with a pinch of salt
HTH - Paul

 

[philaitman]

Think of it like this.
Your shooting in varying light conditions from fairly bright to fairly dark. Your dark shots would require a shutter speed too slow to handhold so you could up the ISO to get a faster shutter speed. Problem is you keep forgetting to lower it so you get noisy shots in the brighter conditions DAMN
Turn on Auto ISO, say you want it to kick in at 1/60th and allow it to go all the way to 1600.
When it gets darker and the shutter speed drops below 1/60th the camera will up the ISO by 1/3rd of a stop to get you back to 1/60th. It gets even darker the camera will up the ISO a bit more so on and so forth.
You go back into daylight bam your ISO drops back to the base level again
It's a great and useful feature. Noise can be dealt with in PP camera shake ruins shots full stop.

 

[Tobers]

Yep - that's right. Take the following situation. You have a particular shot you want to get, lets say it is at a rock concert. You've got a lens with a max aperture of f4, and you need a fast exposure so the band aren't all blurred, say 1/125th of a sec. However, it's quite dim in the club and when you take the shot you find it is very underexposed (too dark) as not enough light is getting into the lens at 1/125th.

There are 3 things you can adjust:

1) aperture: but you are as wide open at f4 as possible so you cant get more light in that way
2) shutter speed: you can make the shutter stay open longer and get more light in, but then the figures on stage get all blurred as they move about.
3) "fool" the camera by increasing the sensitivity of the sensor. This is the "ISO" rating. A higher number makes the sensor more sensitive to light. However, higher ISO means more "noise" in the picture i.e. a grainy picture. ISO 100 is usually the lowest and gives least noise. ISO 3200 is very high and will be very noisy.

So, to get your shot, you can keep the aperture at f4, leave the shutter speed at 1/125th, and increase the ISO from "standard" 100 to say 800 to get your shot.

If you have auto-ISO on your camera, it automatically increases the ISO to a setting which will give you the correct exposure for the shutter & aperture settings you've chosen. In this case, your camera will automatically increase ISO to 800.

If you've got a non-auto-ISO camera like mine, you need to remember to put the ISO up manually. And then you forget you've put it up so when you take pics the next day in the sunshine you cant work out why the pics are all grainy .

Hope this makes sense.

Get "Understanding Exposure" by Bryan Peterson and you'll find it is all beautifully explained.

Tobers

 

[py6km]

Wonderful replies, thank you very much. I now get it - ISO is basically a sensor 'gain' - ramp it up, and get you can reduce the amount of light that needs to fall on the sensor to capture an image (by virtue of shutter speed and/or aperture), but at the cost of increased noise in the image. The auto-ISO basically arms the camera with a third way of helping you to capture an image. Pretty cool - will set it accordingly.

If anyone's interested.....I've been trying to find a nice guide to using the D200 on the web, and discovered the attached - I think it's fairly useful. drphibes was also kind enough to point me in the direction of a useful spreadsheet which gives some examples of custom set ups for the D200 - very nifty. I've had to cut it down to upload, but can point to the website if anyone's interested.

 

[PaulBoy]

There's also the very useful "Digitutor" site from Nikon HERE with help for all the Nikon "family" not just the D200 ... Paul