Aperture Comparison between Fixed lens & DSLR

[WooD]

Originally Posted by Taallyn

It is important for owners of point and shoot cameras to understand why their cameras don't give the "nice, creamy backgrounds" at their camera's f/2.8. The reason is that their camera's f/2.8 is equal to a different aperture for a full frame 35mm camera. Thus, their DoF will be quite a bit larger at any given aperture.

There have been a couple of questions about this in the past week or so.

Shot this with a little Canon S2 IS, background looks pretty "creamy" to me.




Camera: Canon PowerShot S2 IS
Exposure: 0.001 sec (1/800)
Aperture: f/4
Focal Length: 46.3 mm
Exposure Bias: 0/3 EV
Flash: Flash did not fire

[Aperture Nine]

With point and shoot cameras you can easily create the DOF effect in macro shots like yours, but it is almost impossible to get the same effect in portraits and any other kind of shots.

[wulf]

Originally Posted by WooD

Shot this with a little Canon S2 IS, background looks pretty "creamy" to me.

How far away was the subject and how much further was the background? According to the background, P&S f/4 is equivalent to DSLR f/16. Taking your focal length as directly comparable and assuming you were 1' away, I would have a DoF of about 1" and plenty of scope for bokeh if tried my D40 on the same subject at f/16 (using an online DoF calculator). Even stopped down to f/32 the DoF would be only about 2" at that distance (although diffaction would be causing noticeable problems by that point).

You can get similar effects in a portrait IF the subject is close and the background is some distance away but you don't have as much scope - for example, in a full length portrait, the background would need to be much further away to get it blurred.

Wulf

[daft_biker]

Originally Posted by dimitrz

.....(yes a whooping f/64 which no DSLR can beat :-) ).....

Interesting table and I'm sure it's close enough to be useful as a guide to help some understand the effect of format size on DoF. (even if different compacts have slightly different sized sensors)

However, f/64 can be beaten by a SLR (even a film one) if you fit the right lens to it.....for example the Canon MP-E 65mm goes to an effective aperture of f/96 when used at 5:1 and fully stopped down....slap some extension tubes on and you can probably get close to an effective f/200 You'd get fuzzy results due to diffraction at stupidly small apertures but it can still be done.

[daft_biker]

Originally Posted by wulf

How far away was the subject and how much further was the background? According to the background, P&S f/4 is equivalent to DSLR f/16. Taking your focal length as directly comparable and assuming you were 1' away, I would have a DoF of about 1" and plenty of scope for bokeh if tried my D40 on the same subject at f/16 (using an online DoF calculator). Even stopped down to f/32 the DoF would be only about 2" at that distance (although diffaction would be causing noticeable problems by that point).

...
Wulf

Indeed. IIRC the below was taken at f/16 on a 100mm macro lens fitted to a 300D. Magnification about 0.5x.

[dimitrz]

Thanks guys for sharing your expertise & views on the said subject.

Wulf you are always welcome to amend or edit any information as and when required.

Everyone else please feel free to share your thoughts & experience

[dimitrz]

Originally Posted by daft_biker

However, f/64 can be beaten by a SLR (even a film one) if you fit the right lens to it......

Didnt know that

Originally Posted by daft_biker

you can probably get close to an effective f/200 ; You'd get fuzzy results due to diffraction at stupidly small apertures but it can still be done.

Am going fuzzy just thinking of f/200

[sk66]

Originally Posted by vandergus

The f number is the ratio of the focal length to the diameter of the opening that the light enters through. For example, a 50mm lense at f2 has an opening 25mm across.

To be perfectly clear, there is no difference in f-stop number between different formats (sensor sizes) when it comes to how much light the medium is exposed to. F2 is f2 when it comes to exposure. The 35mm equivalent that dimitrz is referring to is the equivalent depth of field. The depth of field is not a function of just the aperture but also of focal length. The dependence on focal length, typically much smaller in a digicam, to have such a large depth of field.

Thanks for the clarification...I was confused on what the f-stop was in relation to (focal length, not max aperture). I probably new that at one time...