New answers tagged

1

Is it better approach to use f1.4 for stars, city/mountains landscapes and other type of photography where object of interest are very far from me and I want to have them sharp? It depends (stars and landscapes have different answer). For stars, you want: The largest sensor you can afford. For most serious astrophotographers, it'll probably be a full ...


0

Most camera lenses are preset with an index mark and a stop for infinity. In other words, turning the focus ring, retracts the optics and the mechanism halts this travel. The lens then exhibits optimum focus for infinity (as far as the eye can see ∞). Not all setups provide such a “stop”. Given no stop, we fall back on the viewfinder / rangefinder method ...


1

Lens design texts often suggest that for some designs, the position of the aperture is relatively critical with regards to vignetting and distortion. However, an MFT camera with a full frame lens only uses the center bit of the imaging circle, so if the adapter causes grave problems in the corners and sides, these problems might be mitigated/attenuated ...


2

As I understand the question, you're asking about lens sharpness/IQ when depth of field is not a concern. Light itself is sharpest when it is not bent through an aperture restriction, but that can't happen. So light is sharpest when it is bent the least... i.e. the largest aperture opening/smallest f#, resulting in the least diffraction. But for that to ...


6

If I'm getting the question correctly, it is about whether at infinity focus you ought to use wider apertures like f/1.4 or narrower apertures like f/11 to get the sharpest results? The answer is, it depends... First let's look at what depth of field actually is at infinity focus. The depth of field depends on three things: Focus distance, focal length, ...


1

I would add that it could be a sticky aperture problem. Whilst in DOF mode the aperture blades did close, during the fast shutter moment, it may not have enough time to react. I had a similar problem with one of my yongnuo lenses. I could temporarily remedy the problem by repeatedly doing a DOF preview until the aperture blades had loosened. When I took ...


1

I agree with user86418's assessment that Jerry Coffin's answer has this backward, though he in turn seems to have conflated numerical aperture with ƒ/number. Quoting outdoorphotographer.com In a variable-aperture zoom ... elements in front of and behind the diaphragm move (and the diaphragm itself moves), so the entrance pupil doesn’t vary in ...


-1

The f-number system is unique in that it is universal. In other words, any lens, on any camera, regardless of focal length or image size, when set to the same f-number, will return an identical exposure. Well, not exactly, but close enough for most every need. In cinematography, a T-stop is favored. This is an f-top that has been calibrated to take into ...


0

Aperture f-numbers are near approximations. And the 1.4x increment is approximately equal to doubling of the aperture area. I.e. a 25mm aperture diameter (entrance pupil) has an area of 490mm; and 1.4 x 25mm = 35mm with an area of 962mm... approximately double the area/light/exposure. If the lens is 50mm in focal length (FL), the 25mm aperture would be f/...


5

A similar aperture numbering system called the U.S. system (Uniform System) was used by the first Kodak cameras (until around 1920s). That system originated in England (1880s). Not 1, 2, 3, 4, but those stops were numbered 1, 2, 4, 8, etc, starting from todays f/4 equivalence. It was more useful than 1, 2, 3, 4 because it represented exposure increase ...


14

What is the purpose ... for the existing convention? Math. It's because in many equations regarding simple optics, the ratio N = ƒ/D (where N is the ƒ-number, and D is the lens (or more often precisely, entrance pupil) diameter) pops up a lot, or the use of the ratio simplifies the expression or understanding of the expression. Example 1: The hyperfocal ...


1

It's mechanical vignetting. The aperture of the rear lens should be wide open and you adjust the aperture of the front lens. See here for more: http://www.coinimaging.com/coupled_lenses.html


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