Well, if your lighting changes (if you're panning to follow something and you sweep across varied sky/land/trees, etc., for example), then whatever you have set won't change but what the camera sets will. That might make a difference...

Aperture Priority and Shutter Speed Priority are semi-automatic modes while Program is fully automatic (regarding aperture-shutter speed pair).VictorBucuresti, Romaniahttp://s106.photobucket.com/albums/m268/victor_petcu/..

Burgesst wrote:.

And program is the same again, you adjust the wheel and bothparameters follow..

So what's the practical difference ???.

Program mode provides a kind of safety net. Let's say for example, you use Shutter priority, and choose 1/500 sec. For a subject in bright light, that might correspond to a lens Aperture of f/8 to give the correct exposure. Then if the lighting changes, or you move into the shade, the required lens aperture might become f/2.8 or f/1.4, for example..

But suppose the camera/lens you are using has a maximum aperture of f/5.6, then the necessary exposure is impossible. So you get under-exposed shots. In program mode, the camera would automatically reduce the shutter speed to maintain the correct exposure..

What this means in practice is that if you use either Aperture or Shutter priority, it becomes *your* responsibility to keep an eye on the settings and make sure what you are doing is reasonable and realistic. Equally true in Manual mode where you set both shutter and aperture, but it's taken for granted that you have checked the settings in this case.Regards,Peter..

Your understanding is exactly right. Which mode you use depends on what is most important to your picture. If you want a high depth-of-field for a landscape, you might set the lens to f/16 in aperture-priority mode, and take whatever shutter speed the camera gives you. if you have a tripod you won;t care what the shutter speed is..

Conversely if you are photographing sports you might set the shutter to 1/1000 sec (in shutter priority mode) to freeze the action, and take whatever aperture the camera gives you; depth of field would a secondary consideration comapred to freezing the action..

P mode will choose both for you, but you might end up with a blurred image if the subject is fast moving and the shutter speed selected by the camera is too slow, or an out-of-focus background is the camera selects a wide aperture with a narrow depth of field when you really needed a large depth of field..

Best wishesMike..

So what's the practical difference ???Cheers..

The clue's in the name I guess. Aperture PRIORITY. Means that it's the most important thing, so you don't want the camera changing it just because the sun came out. Yes, you can change the aperture so that it changes the shutter speed too, but it won't hold that shutter speed unless the light stays exactly the same. When you want to control depth of field, aperture is most important and all you need to know about the shutter speed is that it's fast enough..

Same goes for shutter priority. When you're taking photos of racing cars, who cares about the aperture? You're too busy thinking about shutter speeds so let the camera worry about the aperture..

So it all depends on what you're taking photos of - what your priorities are. Program shift lets you do a bit of everything, but in the end I doubt you'd use it much. Your eye can't keep track of constantly changing apertures and shutter speeds as well as your subject, especially if it's moving..

Androohttp://Androo.smugmug.com..

Thanks, makes sense now. Hadn't considered the situation where the light was changing..

Why don't they say that in the books? Or maybe I just think too much ..

They do say so in the books. It's a constant point of disagreement between me and the guy that teaches the photo course I attend. I just love the speed the semi automatic modes my cam gives me. My teacher swears by full manual.Don't wait for the Nikon D-whatever, have fun now!http://www.flickr.com/photos/j_wijnands/..

Using full manual really takes experience learning to judge the correct combos. It great if you can do it. It's quite hard to do with a compact, because the control are usually rather to awkward..

StephenG.

Fuji S9600Fuji S5200Fuji F30Fuji E900Canon A710ISPCLinuxOS..

They all have advantages: usually I think that something will need a shutter speed of whatever and then set to that and fire away or else I think that some aperture would be best and set to that in "A" and fire away..

But keeping an eye on whatever the thing choses and jumping in to override if need be by using manual or spot metering or c/w etc..

"P" has advantages for grabbing shots and the shift wheel works wonders at times....

Regards, David..

What has been not stated in the above answers is that some dslrs have what is called HYPERPROGRAM. it actually is aversion of program which is you change the wheel when camera is set to aperature or shutter speed and the camera does the other change to keep the exposure correct. hyperprogram is on cmeras that have 2 adjustment wheels and in the program mode one wheel is for shutter speed while the other is for aperature..

It makes the use of program mode a little easier...

When using a flash, it is also possible to set the camera in manual program (usually M)..

The advantage is you can set both the aperture and the shutter speed as you want the and still let the camera adjust the exposure automatically with the flash power..

Stephane - KM Dynax 7DSigma 28-105 - 18-50 - 105 - 170-500KM 100-300 APOhttp://www.chauveau-central.net/gallery2/v/insects2/.

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