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2
votes
1answer
153 views

What is the largest aperture on a commercially available lens? [duplicate]

Out of pure curiosity, what is the largest aperture, or lowest f-stop, a commercially available lens has. I have seen the 50mm prime lens from canon with 1.2, but not lower than that. What are the ...
3
votes
2answers
164 views

How to compare the speed of lenses taking transmission into account?

When comparing the speed of two lenses, you almost exclusively hear about the maximum aperture. This of course makes sense, since at a certain lighting condition, a larger aperture in general allows a ...
2
votes
3answers
252 views

What does “maximum aperture” mean in a camera spec? Where can I get the full aperture range?

I own a Canon S95, and am considering getting a newer model (e.g. Canon S110 or S120), and I'm comparing the specs. According to DPReview.com, the S95 has a maximum aperture of F2.0-F4.9, and the S110 ...
1
vote
1answer
218 views

Size of the entrance pupil vs size of the aperture

I understand that the entrance pupil is the image of the aperture as seen from the front of the lens. However, is the size of the entrance pupil the same as the size of the effective aperture? In ...
0
votes
3answers
193 views

Can I estimate the light gathering power of a lens by measuring size of entrance pupil?

Supposing I have an unknown lens of which I don't know f/# and focal length. I want to estimate the total amount of light that my lens can collect which, I believe, is given by the solid angle that my ...
1
vote
2answers
136 views

Minimum and maximum apertures

Is there such a thing as a maximum aperture that a lens can be open to? What about a minimum aperture that it can be closed to? Do these concepts even make any sense? Is there a lens with the ...
11
votes
4answers
548 views

Why aren't lenses designed with extra large apertures for autofocus beyond what's used for imaging?

Historically, designing large-aperture lenses has been difficult because correcting the optical aberrations that arise from large apertures requires complex designs and very large amounts of glass. ...
3
votes
2answers
353 views

What's the difference between real and effective aperture?

I understand that the simple idea that f-stop is focal length divided by aperture really applies to a simple single-glass lens, not the compound lens systems used to provide good image quality in ...
15
votes
2answers
701 views

Does a specific f number across all lenses denote same amount of light?

When we say a light source emits 1500 lumens of light, it does not really matter if the light source is incandescent, CFL, diode etc. Similarly, when I say f/1.8 can I assume that all lenses pass the ...
16
votes
2answers
734 views

Do rounded edges on aperture blades improve image sharpness, and how?

In the description for the XF lenses for its new X-Pro system, Fujifilm crows: The [XF lenses] all offer precise control over depth-of-field and deliver excellent out-of-focus bokeh thanks to the ...
2
votes
1answer
118 views

Why does an aperture crop the image when you look through a lens itself but not when you look through the viewfinder?

I have been studying lenses for two days now and the aperture is very confusing. Based on the question here it appears that the aperture should not crop the image at all but when I look through a lens ...
7
votes
4answers
840 views

Do bigger focal lengths capture more light?

I never understood what the f really stands for in the f-stop values, like f/1.8. Wikipedia explains it in various articles, but I still find it very confusing. What I understand, though, is that it ...
7
votes
3answers
385 views

What is the limiting factor in lens construction when it comes to f-stop values?

This widely praised Nikon 105mm macro lens has a maximum f-stop value of 2.8. I've held it in my hands, it's a big lens. Meanwhile, this 50mm Nikon lens can go up to f/1.2, despite being 25% cheaper ...
11
votes
4answers
1k views

Is overall light gathering of a lens only dependant on aperture?

My impression is that the aperture value of a lens determines its light gathering ability, but I'm not sure I understand how it works... When considering light gathering in telescopes, it is ...
5
votes
1answer
271 views

What's the history of neutral density filters instead of aperture diaphragms in compact cameras?

Some compact cameras use neutral density filters to control light rather than aperture blades, to avoid the effects of diffraction in tiny sizes. I first heard of this as a feature of the Nokia N8 ...
6
votes
2answers
739 views

How are neutral density filters in compact cameras implemented?

I've read here on this very site that some compact cameras don't use aperture blades to stop down the lens and limit the amount of light hitting the sensor. Stopping down increases diffraction. ...
13
votes
2answers
2k views

Why do zoom lenses and compact cameras have varied maximum aperture across the zoom range?

Why does a camera's maximum (allowed) aperture get smaller when you increase its zoom?
8
votes
6answers
3k views

Technically, why is the out of focus area blurred more when using a bigger aperture?

I'm wondering, technically, why and how does the out of focus areas blur more when using a bigger aperture. I think it'd help a lot if I presented a problem that's been driving me nuts for a long ...
15
votes
5answers
900 views

How do I find the aperture that produces the highest-quality images for a given lens?

I'm not talking about large aperture (f/1.8, f/2.8...), rather, about small apertures (f/18, f/20, f/23...). I read somewhere (actually I think it was on this site, but I don't exactly remember which ...
6
votes
3answers
710 views

How many blades does my lens' aperture diaphragm have when I get 12-pointed starbursts?

Here I figured that my camera has either three or six blades. But yesterday I took another shot at night with the same setup which has twelve srokes: The camera is a Canon 550D and I used the same ...
16
votes
6answers
2k views

Can a smaller sensor's “crop factor” be used to calculate the exact increase in depth of field?

If APS-C and similar crop-sensor digital cameras have a focal length multiplying effect such that a 50mm lens has an apparent focal length closer to the field of view of an 80mm on a full frame ...
1
vote
2answers
575 views

What is the quantitative relation between f/# of the lens (aperture), exposure, and ISO?

Let's say we shoot with a DSLR camera and we have two interchangeable lenses. Lens #1 has aperture f/X, X between 1 and 2 (see below). Lens #2 is f/4.5. Same focal length and other characteristics as ...
40
votes
7answers
5k views

What is a “diffraction limit”?

I've seen the term used, but what is a "diffraction limit", when should I worry about it, and what undesirable effects are a result of it ?
30
votes
5answers
5k views

How do constant aperture lenses work?

Cheaper zoom lenses usually are faster at the wide end and slower at the long end (for example, the $150 Canon EF-S 18-55mm f/3.5-5.6). More expensive constant-aperture zoom lenses have the same ...
28
votes
4answers
2k views

How does aperture work without “cropping” the image hitting the sensor?

I've been teaching myself the various settings in cameras and now have a much fuller understanding of how to use my camera effectively, but one thing is still bugging me. When the aperture size is ...
12
votes
6answers
533 views

Does lens speed still increase meaningfully when the physical aperture is larger than the sensor size?

This question came to me this morning, thinking about 50mm lenses. I have the Pentax 50mm f/1.7 (manual) and it's a very nice lens, but would be considered (relatively) slow on 35mm film, and many ...