Aperture difference between compacts and SLR

[hwchoy]

But as for ISO, I believe IS on a compact effectively cancels out the advantage? Or maybe leaving only 1 stop advantage. That's assuming that no IS/VR lens is used (not exactly affordable to most!).

I also don't understand this. ISO refers to sensitivity but does not measure noise performance. my G5 ISO 50 is about as good as my 20d ISO 400.

 

[hwchoy]

24 f2.8 ===> @f/2.8 len is 8.57 mm diameter
35 f2 ===> @f/2 len is 17.5 mm diameter
50 f1.8 ===> @f/1.8 len is 27.7 mm diameter.
80-200 f2.8 ===> @f/2.8 len is 28-71mm diameter


most of them are already quite big. some are even bigger than the whole size of compact, width-wise.

no sh!t some of the mama lens you can fit the whole prosumer cam inside :sweat:

 

[kniveswood]

I also don't understand this. ISO refers to sensitivity but does not measure noise performance. my G5 ISO 50 is about as good as my 20d ISO 400.

Erm...what I meant is DSLR can bump their ISO higher by about 2-4 stops depending on camera models compared and whether u want to consider a compact's ISO 400 and above usable at all.

And with most new compact's IS, it'll allow you to go 2-3 stops lower in shutter speed. Which I thought effectively cancels much of a DSLR's ISO advantage.

But Clockunder has explained why ISO is better than IS in cases where high shutter speed is necessary and IS won't help.

Err...hope you understand what I was saying in that earlier post now.

 

[hwchoy]

OK I'm a bit dense today. I just weren't able to relate to your point about IS canceling out ISO. probably as you said clockunder has explained why ISO is better, but in my mind, they are two different things although they both do something to the shutter speed.

this is also the reason why people pay big bucks for fast tele lens (e.g. ƒ/2.8) rather than IS on a slower lens (say ƒ/4.0 IS). faster lens allows better lowlight AF, better DOF, and faster shutter at a given ISO.

 

[zcf]

Thanks for your input as well, zcf! Good point about more light for focusing.

But as for ISO, I believe IS on a compact effectively cancels out the advantage? Or maybe leaving only 1 stop advantage. That's assuming that no IS/VR lens is used (not exactly affordable to most!).

There are some DSLR come with in-build AS(CCD base Anti-Shake) at affordable price like KM 5D & 7D which can almost apply on all minolta mount lens .

There will be some new Sony and Pentax DLSR cameras come with similar feature, which can practically use on almost all lens with the brand-specific mounts. So with AS + ISO boost, it's definitely another 2-3 stops better than current prosumer IS only.

 

[Clockunder]

OK I'm a bit dense today. I just weren't able to relate to your point about IS canceling out ISO. probably as you said clockunder has explained why ISO is better, but in my mind, they are two different things although they both do something to the shutter speed.

this is also the reason why people pay big bucks for fast tele lens (e.g. ƒ/2.8) rather than IS on a slower lens (say ƒ/4.0 IS). faster lens allows better lowlight AF, better DOF, and faster shutter at a given ISO.

I was pointing out that IS and higher ISO with lower noise are not perfect substitutes for each other and not that ISO is better than IS. Both have their places.

IS/VR actually does not alter the shutter speed but just compensates for any handshake. In the example I gave earlier, it basically meant that if the focal length is 50mm, then it usually means that the picture needs to be taken at faster than 1/50 if handshake blur is to be avoided. With IS/VR, it can be taken at 1/15 without getting handshake blur in the picture if the hands are not very shaky. This is what is meant by compensate by 2-3 stops by IS/VR and although it mentions shutter speed, it doesn't alter it. However, at 1/15, any subject movement will be captured as motion blur on the picture. If motion blur is to be avoided, then higher ISO with lower noise would be a better alternative in such a situation.

 

[hwchoy]

I was pointing out that IS and higher ISO with lower noise are not perfect substitutes for each other and not that ISO is better than IS. Both have their places.

IS/VR actually does not alter the shutter speed but just compensates for any handshake. In the example I gave earlier, it basically meant that if the focal length is 50mm, then it usually means that the picture needs to be taken at faster than 1/50 if handshake blur is to be avoided. With IS/VR, it can be taken at 1/15 without getting handshake blur in the picture if the hands are not very shaky. This is what is meant by compensate by 2-3 stops by IS/VR and although it mentions shutter speed, it doesn't alter it. However, at 1/15, any subject movement will be captured as motion blur on the picture. If motion blur is to be avoided, then higher ISO with lower noise would be a better alternative in such a situation.

absolutely agree with you, I was sloppy with my terms, and like I said today a bit dense :sweat: