globetrekker Loc: Bend, OR

This is very helpful. Thanks, everyone! I’m learning that the answer to a lot of photography questions is shoot, shoot, and shoot some more! If only I didn’t have to work for a living! :-)

Nevada Chuck

I said nothing about moving subjects because I thought it went without saying that you have to prioritize the three settings based on the demands of the desired result. I thought it was obvious that if you have enough light so that you can shoot the subject at ISO 100, f/16 and 1/60 shutter speed, that you wouldn't choose these settings if the subject is a race horse at the finish line. Clearly, in this example, going to ISO 400 and f/8 would give you a shutter speed of 1/1000, which would probably suffice for the race horse.

globetrekker Loc: Bend, OR

Just noticed that I've gained "regular here" status. Just goes to show how addictive this site is!

abc1234 Loc: Elk Grove Village, Illinois

What may be obvious to us old-timers may not be obvious to the less experience. Judging from the questions that newbies ask and how they interpret answers, I think best not to assume anything.

Likewise about your horse at the finish line. That shutter speed assumes you are in line with the finish line and reasonably close. What if you are up in the grandstand or standing at a 45 degree angle to the finish line? Or the photographer wants motion blur to convey speed?

I feel that advice that says if a, then do b, c, and c is dangerous and misleading. We are all here to learn and help others. One size does not fit all.

Nevada Chuck

Just another statement of the obvious. If motion blur was desired, then this whole discussion is moot.

If one was in geo-synchronous orbit and shooting from a tripod, this would also have an effect on exposure. I say this to make the point that there is always an exception to any rule one cares to follow or formulate.

debbyg Loc: Nebraska

Yes I agree :)...as a newbie myself, I have learned there are many many variables and exceptions to rules...but so much fun learning and finding my way to what I like best. Thank you all for your posts today.

Goldengatebill

My Nikon sets the ISO automaticaly. Of course I can set it to any number I want. What does everyone mean by "noise"? Is this something in the picture?

debbyg Loc: Nebraska

grain = noise the higher the ISO the more noise or grain you get in your picture. I believe someone told me on this site that it really is not noticable until around 1600 and up.

Bobber Loc: Fredericksburg, Texas

Yes noise is a little like film grain, but not quite. If you think of the pixels that create the picture with each little square recording a color and its brightness, then realize that some of them can get disrupted and create a false result here and there over the entire chip area. These disruptions have electronic causes. For instance temperature elevates the number of errant discharges. Sound kinda like a sort of heat rash.

Well, jacking up the chip sensitivity (raising the ISO) will also create more of these little disruptions. Like floaters in one's eyes, they show up much more clearly, when the background is free of objects like plain wall or clear sky.

There is another problem with chips and that is they have hot spots where there is consistently an erring pixel spot. This appears particularly in taking shots of a dark sky background. They show up as tiny spots of intensely lighted color. They will be in every picture in the same places.

In astrophotography where this sort of trouble can be a large pain, one defect removing technique is to shoot what is called dark frames. These will also have defects in them that correspond to those in the rest of the exposures, and can be sandwiched with the sky shots allowing them to be post processed out of the picture in a cancellation process.

Another corrective process is to move the camera very slightly by very small random increments between individual shots to be sandwiched into one picture. This moves any recurring noise about into different locations, so as to blur them out of existence. Or at least nearly so. Good enough. This is called dithering.

On a computer enlarge a picture until it loses definition as a picture and only individual pixels are visible. Do it in a dark area. There you will likely see some "grain" and noise. If too dark then brighten the picture. Actually, the pixels, good or errant, are the grain of the picture corresponding to the film grain, which are silver deposits formed from exposing and chemically developing the film. Any digital photo can be enlarged enough for these pixels to show up prominently. This grain is set by the number of the chip's pixels. That is why chips with more megs of pixels are usually desirable, in that their pictures can be enlarged much more without this "grain" becoming objectionable.

Raising the ISO does not enlarge the pixels, they remain the same size and number. But the price of increased sensitivity is an increase in the pixels sensitivity to heat and firing off false signals. If you want to control this, shoot in sub zero temperatures. Astronomical CCD cameras do just this, they are refrigerated.

At least this is how I understand the function.