Setting the Right ISO/Lots of Lessons Here

[Arthur Morris]

Below is an e-mail exchange that I had with BPNer Bryan Hix. There are lots of great lessons below so be sure to read to the bottom and let loose the questions if need be.

I did forget to mention that if you are desparate for speed, just crank up the ISO to the max...

The gator eating pelican image was created with the Canon 100-400mm IS L lens handheld at 190mm. ISO 6400. Evaluative metering -1/3 stop: 1/1000 sec. at f/5. The image made it to the finals of the BBC Wildlife Photographer of the Year Competition two years running but no cigar....

artie

Hi Bryan,

re:

I have a question that I can't seem to find in both ABP or ABP II. First off, I am so glad I have taken the time to try to learn exposure theory better because I can honestly say I have been doing it wrong.

That is good. ABP is the place to learn exposure theory, and--as you know--the CD book can help you learn to create spot-on exposures with digital cameras by evaluating and adjusting your histograms.

My question is this: what is the best way to determine the ideal ISO setting?

In general I choose the ISO that would give me (approximately) a minimum shutter speed in a given situation. This minimum shutter speed can vary tremendously. For years, I strove to work with shutter speeds of at least 1/60 second when working in low light. I could routinely create sharp images with the 500 and the 600 with the 2X TC at 1/60 sec.. At times I would drop down to 1/30 sec. when working with the prime lenses alone. Things have changed a bit with the 800 f/5.6L lens and its new 4-stop IS system. I am now willing to try working at speeds between 1/6 and 1/30 sec. with the prime lens alone.

If the subject is moving, then I need to be in the 1/250 sec. range that you mentioned. The same goes if I am handholding an intermediate telephoto. If it is flying, I strive for at least 1/500 sec. And I strive for that on the rare occasions that I opt to handhold a long lens.

Another part in my thinking has to go with how much noise I am willing to deal with. As you can see, there are many complex factors involved in choosing an ISO setting.

If I am generally out taking photos in early or late light, I try to pick an ISO setting where I can have the shutter be at least 1/250 with my 500mm and 1.4x TC to stop any blur (not sure if that's even right).

Are you on a tripod or handholding?

At first light, I might be over ISO 1000, but I also might be using my Better Beamer as well. Do I need to have that high of an ISO with a flash or is there some ideal setting for that?

Fill flash will always yield an increase in image sharpness so when using flash you can risk a somewhat lower shutter speed than the 1/60 or 1/30 sec. mentioned above.

Also, once the sun is full strength, do you always try to go as high as you can regardless of flash or not?

(Not sure that I understand your question….) My favorite MIII ISO is 400. In very bright sun I will sometimes drop down to ISO 320 or even 250.

Finally, is there ever a need for auto ISO?

Yes. In two cases (but only if your camera offers the feature) . The first is in very low light when you are trying to create intentionally blurred images. After setting ISO Safety Shift on my MIII body, I set the ISO to 200, set the amount of plus compensation that I need (being careful not to burn the RED channel if there is some color in the sky), and--while working in Tv mode--select a slow shutter speed, the darker it is, the slower speed I set but no slower than 1/4 second and that only for distant flocks. As the light levels increase, I can raise the shutter speeds to more :normal" blur speeds like 1/8, 1/15, and 1/30 second. The camera will set the ISO to the lowest needed to attain the shutter speed that you have set.

When the blurred action is over, I raise my ISO back to 400 (or to 800 if need be), and switch to either Av or Manual mode.

When working from a water craft in low changing light conditions I do somewhat of the opposite. I set up the camera as above but select the minimum shutter speed that I would like to use, usually 1/500 second. Again, the camera will switch to the lowest ISO needed to yield the selected shutter speed (with the compensation already set).

After reading both books, I am using AV mode a lot more versus manual because I tend to take pictures with constantly changing backgrounds and I find that this has helped a lot.

Ah. Once you get comfortable working in manual mode you can put what you've learned to better use by simply setting the correct exposure for the bird (against any background). Then you will not need to be changing from -2/3 to +2 stops when the background changes almost instantaneously.

Let me know if you have any additional questions.