Histogram

I was taking some close up flower photos this weekend. I checked the histogram as I was taking them, and it looked fine. I then put a black backdrop behind the flower, and the histogram became so low that I could not even see it very well. I stopped up and down, but could not get a normal looking histogram. Could someone explain this to me? Some of the pictures still came out fine even with the strange histogram.

I also found that unless I use the manual setting on the istD when the lighting is low, the camera kicks the ISO up to 1600 on it's own.

Hi Ava!

The histogram is counting the number if pixels at each brightness (effectively). When you have a large expanse of black, say a backdrop with a single flower, or you are taking a stain-glass window from inside, a large number of pixels are black. In that case, the histogram will appear very low, or almost non-existant, with relatively few pixels non-black (to the right of the histogram). Your subject will be making a small statistical difference to the histogram.

It's not a bug You just have to understand what the histogram actually represents

Regarding the auto-pushing of the ISO setting - there's a custom function "Auto Sensitivity". You obviously have it enabled. For close up work, or work on a tripod, set this to "off". (Personally I have got it enabled in custom set 1, and disabled in custom set 2 - that way I can quickly switch between tripod and hand held settings.)

Hope that clarifies things for you!
Matt

Thanks Matt! That helps. No matter how many times I read the manual, I find there is still important information that escapes me!