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2
votes
3answers
82 views

What do the specifications mean on the Canon G15's lens?

I am quite new to photography, but spent some days understanding aperture, timing, zoom and ISO. Now I see the values printed on the Canon Powershot G15´s lenses, and I can´t interpret them. I ...
2
votes
1answer
154 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
165 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 ...
1
vote
2answers
185 views

What does the aperture range in a lens name mean?

Regarding lens descriptions, what does the relationship between aperture range f/3.5-6.3 and focal length range 18-270mm mean? How does this work?
2
votes
3answers
256 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 ...
2
votes
6answers
384 views

Why are fixed-aperture lenses not more popular?

Lenses come in different varieties: zoom and prime, different focal lengths, different zoom ranges, with and without optical stabilization, and so forth. Why don't we have fixed-aperture lenses for ...
4
votes
4answers
396 views

Who tells my camera which apertures my lens has

When I mount one of my lenses on my camera, my camera knows which apertures the lens has. So I ask my self: Why does my camera know that for example lens XY has a max. aperture of 2.8 and a min. ...
18
votes
5answers
657 views

Why do two lenses with the same F-number give different amount of light?

Why do the following two lenses provide different amount of light? In both images we have fixed focusing distance, distance to the object, ISO, shutter speed and F-number.
1
vote
2answers
220 views

Help me understand effective f-number

If I set a lens to, say, f/2 but my focus is set to its closest point, my effective f-number won't be f/2 any more but it will be higher by a factor that depends on focal length, image magnification ...
1
vote
1answer
219 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 ...
2
votes
2answers
166 views

Why does oil leak from the aperture ring of old lenses?

I'm assuming that the oil was there initially to lubricate the aperture blades, but why does it leak out?
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 ...
3
votes
1answer
82 views

Lens f-number and speed on adapted lenses

A lens has a focal length, and its entrance pupil has a diameter. The ratio of these is an f-number. The size of the entrance pupil is limited by the size of the front element, and we describe lenses ...
13
votes
2answers
2k views

How iPhone 5S can have such a big aperture? f/2.2?

I thought that in order to have a big aperture such as f/2.2 a big amount of light should be able to enter to the sensor and in order to do it, a big lens was needed. How is it possible that in the ...
0
votes
5answers
696 views

is the Nikon 35mm f/1.8 worth it after i have the kit lenses? [duplicate]

I have a Nikon DX (D5100) camera with the two most basic kit lenses: 18-55mm f/3.5-5.6 VR and 55-200mm f/4-5.6 VR. These two lenses cover lots of scenarios, but I'm starting to believe there is more ...
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 ...
10
votes
1answer
336 views

What is a “De-clicked” aperture control ring?

The Samyang 85mm T1.5 Cine Lens featured a "De-clicked" aperture control ring. What exactly is it?
2
votes
2answers
215 views

Is there any practical way to measure the T-stop of a lens?

T-stop measures actual light transmission in a lens. Therefore, different f/2.8 lenses can have different T-stops. T-stops are usually only given for cine lenses. For photography lenses, is there any ...
4
votes
4answers
680 views

Which aperture is the sharpest in the lens that come with Nikon d3100?

Wich aperture is the sharpest in the lens that come with Nikon d3100? I'm new to photograpy and I read about the "sharpest aperture" property that lenses have, but I read it changes depending on the ...
5
votes
1answer
445 views

Why do Canon lenses stay wide open when off camera, but Nikkor lenses keep tight aperture?

I have only noticed this for a handful of lenses so I am probably wrong in saying that all Nikon and all Canon lenses follow suit. But from those I have seen, Nikon tend to close the iris when removed ...
7
votes
2answers
456 views

Do lenses with the same f-stop but different focal length gather the same amount of light? [duplicate]

I'm taking images of a light source in a scientific labratory, and I thought I had a good grasp on all these things, but now i'm second guessing myself after some results. The most important thing is ...
3
votes
4answers
440 views

How to fix a Nikon 100mm f/2.8 Series E lens not being properly recognized on a D300?

I have a Nikon 100mm f/2.8 Series E mounted on my D300. When I set the aperture on 2.8 on the lens, it is seen as 1.8 on the D300. At its maximum, when set at f/22 on the lens, it is seen at f/16 on ...
3
votes
4answers
484 views

Are there any lenses have smaller apertures than f/32?

While most photographers prefer fast lenses that range down to f/1.2, are there any lenses that go smaller than f/32? If there are, what is so special about those lenses that an aperture of f/32 ...
2
votes
1answer
247 views

How to fix stuck aperture?

I have a Micro-Nikkor 55 mm 1:2.8 lens. The aperture appears to be stuck. Is it worth trying to repair the lens? Are there any good guides for disassembling the lens?
3
votes
4answers
370 views

How is it possible to have shallow depth of field with a small aperture? (The tele-macro paradox.)

Some longer tele lenses have a macro mode that allows for really shallow depth of field that have a lot of background melting when using relatively narrow apertures; like f/4.5-6. I have tried and ...
3
votes
1answer
283 views

How do I properly understand what f-stop is? [duplicate]

I don't quite understand why most lenses seem to have approximately the same diameter aperture regardless of focal length. F-stop is, by definition, a ratio of focal length to diameter, so a 20mm ...
15
votes
2answers
702 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 ...
4
votes
2answers
1k views

Why does higher aperture (less light) make an image sharper?

Why does higher aperture, less light, make an image sharper? Or rather make everything in focus? And how does this lead to lenses having a sweet spot in sharpness?
1
vote
1answer
279 views

Aperture not stopping down on Tamron lens

I have an EF-mount Tamron 70-300mm f4-5.6 lens that seems to have developed a problem. On all focal lengths from 70mm to approx. 200mm, the lens works flawlessly. When the zoom ring goes above 200mm, ...
4
votes
9answers
738 views

Why would a serious photographer buy a lens slower than f/2.8?

It seems to me that the general idea is that, once you start getting to become a decent photographer and are really moving beyond your kit lenses, you shouldn't be looking at anything slower then ...
2
votes
1answer
184 views

Why do the Nikon V1 lens' websites seem to give different f-stops than the lenses? [duplicate]

Possible Duplicate: How can aperture be f/11 on a lens with an aperture range designation of 3.5-5.5? I am a recent (and so far quite pleased) owner of a Nikon V1. I am in the process of ...
16
votes
2answers
735 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 ...
16
votes
2answers
4k views

What is T-number / T-stop?

Usually, when discussing aperture of a lens, F-stop and F-number are used for quantifying. But some photographers, and especially videographers, also mention T-stop. The concept and numbering used ...
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 ...
6
votes
2answers
484 views

What is the effective aperture of two stacked lenses for macro?

Is there a way to calculate the aperture of two lenses stacked together for macro? In my specific case, I have 90mm f/2.8 and 18mm 1/3.5 lenses.
3
votes
5answers
3k views

In what kind of scenes does it make sense to use f/1.4 aperture?

I have been told that it is difficult to focus with an aperture of f/1.4. So, in which kind of scenes does it actually make sense to use the f/1.4? In portraits they say that it is important to keep ...
1
vote
1answer
597 views

Why does the max aperture change when use Nikon 60mm AF-D Micro on D90 camera?

I have found that my Nikon 60mm Micro AF-D changes aperture from 2.8 to 3.2 when used with a D90. I have tried both A and M mode. Is it by design? Why? I intend to buy Nikon 50mm 1.4 AF-D, but it ...
3
votes
1answer
546 views

Does maximum aperture change with focus distance with the Canon 60mm f/2.8 macro lens?

This site says The Canon EF-S 60mm f/2.8 Macro USM Lens loses 1/2 stop at 1:5, 1 stop at 1:3, 1.5 stops at 1:1.5 and 2 stops at 1:1 (lifesize). Can anyone confirm that at 1:5 magnification, ...
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 ...
8
votes
4answers
530 views

What is the technical name for a zoom lens which has a fixed maximum aperture?

What is the technical name for a lens which has the same maximum aperture throughout the entire zoom range?
19
votes
3answers
2k views

Why do wide angle prime lenses have relatively small apertures?

I've noticed that many of the wide angle prime lenses (at least for Canon) have somewhat smaller apertures than their normal or telephoto counterparts. E.g. the regular Canon 24mm prime is f/2.8 while ...
6
votes
6answers
1k views

Is it important that the Canon 1DX isn't specified to autofocus with lenses slower than f/5.6? [closed]

Seeking the lens market AND the related info WRT Canon 1D X, I found some things which seems concerning: 1st, a note from Canon's Chuck Westerfall (see here) saying: “AF is unavailable on the ...
1
vote
0answers
220 views

Nikkor 50mm F1.4D vs. Nikkor 50mm F1.8D [duplicate]

Possible Duplicate: Is there a noticeable difference between 1.8 and 1.4 prime lens? I am a new to DSLR cameras and I just recently got my Nikon D5100 camera. I am now considering buying a ...
2
votes
4answers
292 views

Why does my camera's meter suggest the same exposure time for lenses with different apertures?

On the same camera body (Canon 1Ds MkII) at the same ISO setting (400) and with no filters attached, two different lenses give the same exposure time (0.4s) at very different apertures. The lenses and ...
4
votes
2answers
921 views

Why f/22 is the highest possible setting for the aperture diaphragm?

My first DSLR camera was Canon EOS 350D. Now I've got an upgrade to Nikon D90. Both were/are with the kit lens. Whenever I'm taking a picture with biggest zoom (55mm on Canon, 105mm on Nikon) the ...
-1
votes
1answer
991 views

What does the F number in a lens name mean? [duplicate]

Possible Duplicate: What does the f-stop printed on the lens refer to? I understand that for a DSLR you can modify the aperture(the F number) to allow more or less light to enter the ...
-1
votes
2answers
496 views

How do I decide the best aperture to use with my Canon 18-200mm lens and 50D?

I am using a Canon 50D with the 18-200mm lens it came with. Some of my pictures turn out un-sharp, even taking metering and Auto Focus points into consideration. I wonder if this is caused by my ...
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?
4
votes
2answers
733 views

What's the base f-stop when counting an ideal f-stop for lens?

I've read a lot around this site that an ideal quality of the lens is achieved when using f-stop roughly 2 stops slower than the fastest value of the lens. Firstly, I'm not exactly sure what "2 ...
14
votes
4answers
2k views

What is a “fast” lens?

I've been reading lots of camera reviews lately and have ran across several references to "fast" lenses. What exactly is a fast lens and what are its advantages compared to other lenses?