All Questions
14
questions
0
votes
1
answer
72
views
Question on f-number and exposure [duplicate]
Is there any mathematical proof to show that the exposure in a camera is independent of the focal length used, if the f-number (ratio of focal length to lens diameter) remains constant?
- 177
1
vote
2
answers
718
views
Relationship between f-number and amount of light being let into the lens system [duplicate]
Why does smaller f-number imply greater aperture diameter and consequently, greater amount of light entering the lens of a camera?
As evidenced from my study across a number of resources, an absolute ...
- 177
1
vote
1
answer
451
views
Is a lense with an aperture larger than f/8 useful with an EOS 80 D?
I have a EOS 80D and supposedly it has a max aperture of f/8. Does this mean that my camera can't take advantage of lenses with larger aperture? E.G. This one for example:
Canon EF-S 24mm Camera ...
- 113
1
vote
3
answers
8k
views
What is the sweet spot of the Canon's 18-55mm IS STM lens?
I'm plannning to photograph negative film like this. And I would like to know what would be the sweet spot of my lens to achieve best sharpness possible, what f stop and at what mm I should be ...
- 459
15
votes
3
answers
2k
views
How do zoom lenses restrict their widest aperture at the telephoto end?
Does the aperture ring lock the apertures beyond, say 5.6 at length lens's telephoto end?
Does the lens introduce an obstacle to the aperture ring so the lens can't be opened anymore beyond the ...
- 1,515
0
votes
6
answers
320
views
Is the wide aperture and bokeh of a 50mm prime more important than getting to the 70-90mm range for portraits?
I've a Pentax K-30 with the following lens:
Pentax-M 50mm 1.7 manual focus
Tamron 17-50mm 2.8 autofocus
Pentax 55-300mm 4-5.6 autofocus
Considering that :
Pentax 50mm has the nicest bokeh and ...
- 461
2
votes
1
answer
969
views
Why don't all zoom lenses have variable f-numbers? [duplicate]
As I understand it, the f-number is a ratio between the focal length and the aperture diameter. A zoom lens can change focal length, but shouldn't the maximum aperture be a fixed size? If so, that ...
- 123
5
votes
1
answer
483
views
What prevents a f/1.8, 24 mm - 70 mm or similar range zoom lens from being made? [duplicate]
I see that it is common to have professional grade lenses such as 24-70mm lenses made at f/2.8. After using a 50mm/1.8, I was wondering what would prevent a more versatile zoom lens to be made that ...
- 249
1
vote
1
answer
3k
views
Does the Canon EF-S 24mm f/2.8 STM Lens offer any significant advantage over the Canon 18-55mm IS II at a 24mm focal length?
Does the Canon EF-S 24mm f/2.8 STM Lens offer any significant advantage over the Canon 18-55mm IS II at a 24mm focal length (the kit lens for my T3i)?
I'm looking for a cheap lens that offers a wide ...
- 13
2
votes
3
answers
2k
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 ...
- 195
2
votes
2
answers
2k
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 ...
- 265
5
votes
2
answers
4k
views
Is the size of the entrance pupil the same as the size of the effective 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 ...
- 265
12
votes
2
answers
3k
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 ...
- 223
3
votes
1
answer
433
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 ...
- 1,888
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