Implications of Low Noise

[Rayz]

One of the great advantages of the small format, point & shoot, pocket digicam, is great DoF at small f stops, eg. F2.8.

My second digital camera, the tiny Sony DCS T1, has a smaller sensor than the usual 2/3rds format. The difference in DoF between that and my Canon D60 is about 2.5 f stops. By that, I mean that f2.8 on the Sony T1, with the same Field of View, is equal to f6.3 on the D60 for the same DoF.

The implications are quite clear. In low lighting, the samll format pocket digicam has the advantage. Well, maybe it does in comparison with my old D60 - but I suggest not with the 20d.

Small digicams are generally very noisy above 200 ISO. A camera like the 20D can give acceptable results at 800 or even 1600 ISO.

There's no advantage to the small digicam other than size, weight and cost.

There are advantages to the larger format in all respects except size, weight and cost.

[Jesper]

One of the great advantages of the small format, point & shoot, pocket digicam, is great DoF at small f stops, eg. F2.8.
I'm sure a lot of people won't agree that the great DOF at large apertures is a great advantage. Sometimes you want a shallow DOF, for example to get your subject sharp while blurring the background. That's almost impossible to do with a small-sensor digicam.

[Rayz]

Great DoF at fast speeds is an advantage of the smaller format. Inability to create shallow DoF is a disadvantage.

As I said, weight , size and cost are the only advantages of the smaller format. The larger format has all the other advantages that you can imagine :) .

[Andy_T]

The implications are quite clear. In low lighting, the samll format pocket digicam has the advantage. Well, maybe it does in comparison with my old D60 - but I suggest not with the 20d.


Maybe I'm missing something here, but according to my knowledge and experience, it's just the opposite :roll:.

On my G2 (qualifies as a compact digicam), I almost exclusively use ISO 50 in order to get shots with little ISO noise. Try hand holding a low light shot with that... :cry:

The test shots I've seen from the DRebel and 10D suggest that these yield about the same noise when using ISO 800 (because the 3x larger photosites collect 3x as much light).

And although f/2 (as largest aperture on the G2) is better than, say f/4.5 on the Rebel kit lens, there is no way it will compensate a difference in ISO from 50:800.

And don't mistake DOF for exposure. Using f/2.0 and 1/100 seconds with ISO 50 you will get a perfectly sharp ... but unfortunataly completely underexposed ... photo.

Best regards,
Andy

[Rayz]

And although f/2 (as largest aperture on the G2) is better than, say f/4.5 on the Rebel kit lens, there is no way it will compensate a difference in ISO from 50:800.


Andy

As I understand, the 20D sensor is about 2.2x the height of the 2/3rd format G2 sensor. Call it 2.5x because the aspect ratios are different and therefore precise comparisons are difficult.

To get the same DoF with a 20D as you get with the G2, you have to use an F stop 2.5x greater, ie. F2 on the G2 = F5 on the 20D; F8 on the G2 = F20 on the 20D.

If we take your example using F2 on the G2 at 50 ISO for the least noise and the exposure is 1/30th, then to take the same shot with a 20D with same DoF at a hand holdable 1/30th, you'll need to use F5 in conjunction with around 300 ISO (50 doubled 2.5x). In practice you're going to use either 200 or 400 ISO.

The question is, which shot will show the least noise? It will not always be the larger format. Comparing old technology G2 with new technology 20D I'd have little hesitation in predicting the 20D at 400 ISO would show less noise (as well as the 300D and 10D as your post implies).

However, I recently did such a comparison with my D60 and Sony DSC T1 which has an even smaller sensor than the G2. To get the same DoF and shutter speed with my D60, adjusting focal length to get the same FoV, I had to bump up the ISO on the D60 to 800. The D60 shots showed significantly greater noise and less detail in the shadows.

Conclusion? In certain circumstances this ultra miniature T1 that'll sit comfortably in a shirt pocket, can produce superior images to the D60 (but not the 20D, I'll bet :D )