I got to learn about a useful DSLR feature called auto ISO.
A friend brought in his mint Nikon D90 and let me play with it. He had on the Sigma 17-70mm f/2.8-4.5 HSM macro lens and I was really impressed. It’s not a D700 but for someone like me it’s really good. Low noise at high ISO (compared to my D60), good color handling, and it’s fast.
We switched lenses for comparison and I was struck how his D90 took better exposed pictures than my D60. I took pictures of the same things using both the D90 and the D60. Same lens, but the D90’s pictures handled poorly lit subjects better.
The D90 is a more current model but the difference was (wait for it) night and day. Getting home I found the answer once I cracked open the manual. His D90 had auto ISO turned on, while my D60 had it turned off.
Auto ISO on the Nikon D60 works like this: You set the maximum ISO sensitivity and the minimum shutter speed. The minimum shutter speed is what triggers the auto ISO. Right now my maximum sensitivity is set to ISO 1600 and my minimum shutter speed is 1/15th of a second. Using a flash turns off auto ISO. I leave my camera set to ISO 200.
Most of my pictures are taken in P mode. When the lighting works out that the shutter speed takes longer than 1/15 of a second, the camera will automatically raises the ISO from 200 to whatever works out to get the exposure time back down to 1/15 of a second.
Here’s an example using my son (he was the star student today in his class, way to go!) I set the minimum exposure for auto to 1/8 of a second from my usual 1/15. I did this because my light is poor right now and at 1/15 I was shooting up to ISO 1400.
Both are at f/3.5 and the D60 was in P mode. The picture on the left is with auto ISO turned off, ISO 200 and exposed at 1/2 second. The one on the right has auto ISO turned on. This raised the ISO from 200 to 640 and is exposed at 1/8 of a second. Even with VR 1/2 of a second suffers from hand shake.
It’s not perfect, and if I were using manual mode I would want to turn off all auto settings. But here it reduced the exposure time from 1/2 a second to the minimum 1/8 of a second.
For what I take pictures of it’s very useful; I almost never use the built in flash and don’t yet own a SB-600. As long as my shutter speed remains at or above 1/15 this will not be used. Lower than 1/15 and I’ll get better pictures.
Tomorrow I’m going to a 4 year old’s birthday party so I’ll see how this works in practice.
Update: The day after I posted this, I went to the New York Hall of Science with Lily and the kids. We attended a birthday party for a 4 year old and I borrowed my Dad’s SB-600 flash.
Auto ISO did get engaged with the flash on. I left my camera set to ISO 200 and when the bounce was not enough to get it over the 1/15 second minimum, the ISO was bumped up. This is one that I was surprise to see it get a small boost to ISO 280:
I need to look into this some more. With the flash, the exposure was dialed down to 1/60th of a second. I’m not complaining but I’d like to firm up my understanding.
Overall I took +300 shots and I liked the results. You can see the 40 pictures I posted with a SB-600 and auto ISO turned on Flickr.
