Hi, read a book saying that f/2.8 is somewhat equivalent to f/11 or f/12 on a dslr. is this true? how to calculate the difference, and why do the makers not make the aperture reading the same on both kinds of cameras? :dunno:
is an f/2.8 on a digital cam equivalent to a smaller aperture in a dslr?
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asturias105 said:
the DOF is equivalent to around F/11 - F/14
F/2.8 of light and brightness but F/11 of DOF effect
No, f/2.8 is the same on digicam or DSLR. But the depth of field of a digicam is much larger than that of a DSLR, so the DOF of a digicam at f/2.8 might be equivalent to f/11 on a DSLR. The exact aperture it is equivalent to depends on the ratio of the sensor sizes.
the aperture number is merely a ratio of the focal length of the lens.
how to compare apples with oranges?
how to compare apples with oranges?
f/2.8 on a digicam with a lens of 7mm focal length (let's say 35mm equivalent) @ 7mm (widest) gives an aperture of just 2.5mm.
f/2.8 on a 35mm camera gives an aperture of 12.5mm.
As you can see, opening is smaller.
Not sure if the logic is right, but now if you take a 2.5mm aperture (opening) and apply it to a 35mm camera with a 35mm lens, you get an f-number of 35mm/2.5mm = f/14.
Regards
CK
f/2.8 on a 35mm camera gives an aperture of 12.5mm.
As you can see, opening is smaller.
Not sure if the logic is right, but now if you take a 2.5mm aperture (opening) and apply it to a 35mm camera with a 35mm lens, you get an f-number of 35mm/2.5mm = f/14.
Regards
CK
ok let me get this correct.
so f/2.8 on a digicam and a dslr is the same aperture size except that the DOF is different due to the sensor size and focal length of the lens?
ckiang: are u suggesting the aperture size is actually different?(2.5mm and 12.5mm)
or is it the f number is the same for both, but the aperture size is actually different and DOF is therefore different? Add to it diff sensor size and diff focal length?
so f/2.8 on a digicam and a dslr is the same aperture size except that the DOF is different due to the sensor size and focal length of the lens?
ckiang: are u suggesting the aperture size is actually different?(2.5mm and 12.5mm)
or is it the f number is the same for both, but the aperture size is actually different and DOF is therefore different? Add to it diff sensor size and diff focal length?
I raised a similar question some time back and it was a good discussion with
many educational feedback. See this thread:
http://forums.clubsnap.org/showthread.php?t=101263
Cheers,
L.Lee
many educational feedback. See this thread:
http://forums.clubsnap.org/showthread.php?t=101263
Cheers,
L.Lee
vinvin said:
Nope. The actual physical size of the aperture is different. Please note f/2.8 is a RATIO, not an actual size. Think about it, my cell-phone camera also has a f/2.8 lens, but the entire phone itself is not much bigger than the rear opening on a 70-200/2.8 lens, how can the actual aperture size be the same?
vinvin said:
Yes, it is correct.
vinvin said:
The DOF is as you have suggested. Due to the smaller sensor size and the relation of focal length and the distance from lens to sensor, a f/2.8 lens made for a smaller sensor will give you much more DOF than one made for a larger sensor.
How about DOF effect of a standard 35mm lens on a cropped sensor? Hah! Another kettle of fish.......
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