I have a Canon 70-300mm IS USM, with filter thread diameter 58mm. Would it make any difference if I upgraded to a lens with greater diameter, like 72 or 77mm ? My guess is - increasing lens diameter sort of "lets in" more light, hence the shutter speed can be lower, and the possibility for shake reduces even at longer focal lengths. Does this argument make any sense ?
And if it does, then is having a 300mm lens with a 58mm diameter and IS (Image Stabilization) any better than a 300mm lens with a 77mm diameter without IS ??
Would much appreciate any comments.
Btw - this is my first posting on this board. LL looks like a high quality site, and the forum has high quality inputs.
Full Version: Lens Diameter
A more useful and reliable measure. instead of filter thread size, is the lens' maximum f/stop.
Rather than type out the explanation read the Wikipedia entry hereWikipedia entry here
You should be aware that shutter speed is proportional to the aperture...ie. the greater the aperture (light admitted) the greater the shutter speed.
What the Wikipedia entry elucidates is that the f-stop in the light vs shitter speed vs aperture is a function of the ratio between the focal length and the physical aperture size. Therefore, for a given focal length if the aperture diameter increases then the f/stop reduces and you can use a faster shutter. i.e. going from 58mm to 77mm increases the aperture, reduces the f/stop and increases maximum possible shutter speed that you can use (assuming constant ISO and focal length).
Once you are comfortable with that concept considering finding out:
1/ How varying the aperture diameter changes the depth of field (including the impact of crop factor on the calculations).
2/ How varying the aperture of the lens affects sharpness - lens aberations at the wide open position and diffraction when it is stopped down.
If you search the forum there is plenty of discussion on both subjects (ad nauseum to many people who have been here before
and probably ranks up there with how many angels can you get to dance on the head of a pixel before the noise of the disco drowns them out?).
There is plenty of discussion on the forum
You should be aware that shutter speed is proportional to the aperture...ie. the greater the aperture (light admitted) the greater the shutter speed.
What the Wikipedia entry elucidates is that the f-stop in the light vs shitter speed vs aperture is a function of the ratio between the focal length and the physical aperture size. Therefore, for a given focal length if the aperture diameter increases then the f/stop reduces and you can use a faster shutter. i.e. going from 58mm to 77mm increases the aperture, reduces the f/stop and increases maximum possible shutter speed that you can use (assuming constant ISO and focal length).
Once you are comfortable with that concept considering finding out:
1/ How varying the aperture diameter changes the depth of field (including the impact of crop factor on the calculations).
2/ How varying the aperture of the lens affects sharpness - lens aberations at the wide open position and diffraction when it is stopped down.
If you search the forum there is plenty of discussion on both subjects (ad nauseum to many people who have been here before
and probably ranks up there with how many angels can you get to dance on the head of a pixel before the noise of the disco drowns them out?).There is plenty of discussion on the forum
QUOTE (DiaAzul @ Apr 13 2007, 01:04 PM)
What the Wikipedia entry elucidates is that the f-stop in the light vs shitter speed vs aperture is a function of the ratio between the focal length and the physical aperture size. Therefore, for a given focal length if the aperture diameter increases then the f/stop reduces and you can use a faster shutter. i.e. going from 58mm to 77mm increases the aperture, reduces the f/stop and increases maximum possible shutter speed that you can use (assuming constant ISO and focal length).
Great misspelling diaazul. It gave me a laugh anyway.
On a serious note; smaller filters cost much less money.
Smaller filters usually cost less.
The Canon 300 f/28 uses a 52mm drop in filter, not a screw in. Maximum f/stop usually works better for this reason and a zoom lens may change maximum f/stop while zooming but the filter size is fixed.
Compared to the cost of the lens, the filters needed may be small.
The Canon 300 f/28 uses a 52mm drop in filter, not a screw in. Maximum f/stop usually works better for this reason and a zoom lens may change maximum f/stop while zooming but the filter size is fixed.
Compared to the cost of the lens, the filters needed may be small.
Thank you gentlemen.
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