Digital cameras 101

[rhinorick]

I took some photos at our church's Christmas play and then went back to the next showing and took more photos.

I used the same ISO settings, shutter speeds, etc. And as far as I know, the lighting was exactly the same.

The photos at the second show turned out much better - less noise.

The only difference, that I know of, was that I was closer the second time, and therefore used a shorter focal length.

Can that make that much of a difference?  

[bdery]

Hi,

I can only guess that you used a lens with a variable aperture (kit lenses are this way, for instance) and that you used a shorter focal length. This would result in a faster shutter speed, and less noise because of that.

Otherwise, I can't see how similar ISO values and shutter speeds would yild different results in similar situations. Maybe some examples would help.

[rhinorick]

Thanks for the reply bdery.

I used manual settings, so I set the shutter speed and aperture manually, and used pretty much the same settings for both each time.

The only real difference was the focal length, as I mentioned.  I just didn't realize that a shorter focal length would yield less noise/graininess.

[bdery]

The only real difference was the focal length, as I mentioned.  I just didn't realize that a shorter focal length would yield less noise/graininess.

The focal length should have no effect on noise. The only thing it should affect is the stability (you run less risks of creating motion blur with a shorter focal length) and the lens performances (chromatic aberration, sharpness, etc). Noise is linked to the sensor and the exposure time.

I would be interested to se samples to try to understand this phenomenon better.

One other hypothesis : since you changed the focal length, if you framed the scenes similarly, you might have to zoom more on your file (use a bigger enlargment) to see the same level of details. Could that be it?

[rhinorick]

Hmmmm.  Never mind.    My mistake.  

In reviewing the EXIF data on my photos, it looks like I took most of the shots in the second set at a different (lower) ISO setting than the first set.  I did not realize I had done that.  

I guess being closer and using a shorter focal length allowed more light onto the sensor and allowed a lower ISO.  Does that make sense?

Anyway ... my original question was based on inaccurate info.  

Thanks for your help anyway.  I have at least learned a few things in the discussion.

[bdery]

I guess being closer and using a shorter focal length allowed more light onto the sensor and allowed a lower ISO.  Does that make sense?

Only if, as I wrote, your lens has a variable aperture (a maximum aperture that changes with focal length).

[ShutterbugGail]

I guess being closer and using a shorter focal length allowed more light onto the sensor and allowed a lower ISO.  Does that make sense?

When taking photos inside and hand-holding the camera, I always try to shoot at the widest angle when using a zoom lens. Yes, for lenses with variable apertures, the aperture is largest at the widest focal length and lets more light in. My guess is that you have your camera set to auto ISO.

[rhinorick]

Thanks for everyone's help and input.  

I was using all manual settings.  I just simply used a lower ISO value in the later shooting session, as I pointed out above.

One of my "rules of photography" ... watch those settings!!!  :-P

Merry Christmas everyone!!