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Results tagged with f-stop
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user 1375
The f-stop of an optical system expresses the diameter of the entrance pupil in terms of the focal length of the lens; in simpler terms, the f-stop is the focal length divided by the "effective" aperture diameter. It is a dimensionless number that is a quantitative measure of lens speed, an important concept in photography.
1
vote
What is the useful range of apertures for lenses?
Every stop has a use, otherwise they wouldn't exit.
Typically at the widest end (f/1.8) the lens will suffer from aberrations and produce a slightly softer image. But there are times you need the lig …
- 119k
0
votes
How is depth of field usually measured and how can I get depth of field measurements for a lens
If you are comparing lenses / cameras with roughly equal field of view then the quantity you want to look at to determine the level of background blur is the diameter of the entrance pupil.
This is e …
- 119k
8
votes
Accepted
Do top-of-the-line lenses transmit more light at the same f-stop?
No, it won't be anything like a full stop, but there is probably a small advantage.
Our friends over at DXO mark test transmission of lenses, though only wide open, and they don't have a pair of L no …
- 119k
2
votes
What does the f-stop printed on the lens refer to?
When printed on a lens the f-stop is usually expressed as a ratio with a colon (i.e. 1:1.4) rather than the more usual f/1.4, however it still refers to the maximum apparent aperture divided by the fo …
- 119k
9
votes
Why don't compact digital cameras have the aperture range of DSLRs?
Yes, it's a physical limitation due to the size of the sensor (and thus the size of the individual photosites) that means that diffraction becomes a limiting factor sooner than it does with DSLRs, hen …
- 119k
5
votes
What shutter speed to use when shooting video?
What shutter speed should I use? I have read that it should be double the FPS. Why so? What if I break this rule?
The double the framerate suggestion comes from the film days when the shutter wou …
- 119k
1
vote
Is there any way to stop down the aperture of a Canon PowerShot SD780 IS?
There is the Canon Hack Development Kit (CHDK):
http://chdk.wikia.com/wiki/CHDK
Which states it supports the SD780. It's fairly safe in that you load a fully hacked version of the firmware which get …
- 119k
2
votes
Accepted
What's the difference between real and effective aperture?
The difference is that almost everything you need to know as a photographer depends on the effective aperture (also known as the entrance pupil diameter) whereas the actual size of the diaphragm is on …
- 119k
8
votes
Does a specific f number across all lenses denote same amount of light?
Basically, yes. From an optical perspective assuming you compose the shots similarly then different lenses with the same f/number will produce the same exposure. This is why the f/number is specified …
- 119k