Tagged Questions
1
vote
3answers
204 views
How to get focal length from a camera specification which gives a value like “4.5-22.5”?
I am using a Sony W520 camera. The specifications mention
Focal Length (f= mm) 4.5-22.5. What number should I take? The lower value or the higher? And if not both of them, then how to calculate actual ...
4
votes
2answers
360 views
Why does calculated distance of an object in an image vary when zooming?
I would like to calculate the distance of an object from my camera, so i used the formula given in this question and I got a very good answer, but I've found that when I zoom and take the picture and ...
3
votes
2answers
524 views
What is the conversion between focal length and times zoom? [duplicate]
Possible Duplicate:
How do I convert lens mm to optical zoom times?
What is the conversion between focal length in mm (e.g. 50mm) and x zoom (e.g. 20x) commonly used in compact cameras? Is ...
5
votes
1answer
389 views
Should my flash zoom match my lens focal length or its 35mm equivalent?
I have a camera with an APS-C sized sensor. Should my flash zoom match my lens's actual focal length or its 35mm equivalent?
I am hoping that someone can shed some scientific light to this matter.
1
vote
1answer
2k views
Why does my aperture setting change as I zoom the lens on my Nikon D90?
I am new to the photography field and this something which I am not able to understand. I am playing around with my Nikon D90 along with its kit lens (18-105mm).
While reading about Depth of preview, ...
4
votes
2answers
640 views
Is it normal for focal length to change while focusing?
When I change the focus distance on my Pentax 55-300mm lens, the focal length appears to change. More specifically, the lens appears to zoom in as I focus towards the minimum focusing distance. This ...
7
votes
1answer
862 views
Why does the maximum aperture change with focal length? [duplicate]
Possible Duplicate:
Why do zoom lenses and compact cameras have varied maximum aperture across the zoom range?
It is rather common with zooms that the maximum aperture changes (in fact, ...
18
votes
5answers
26k views
How do I convert lens mm to optical zoom times?
What is the rule to convert the 'mm' notation to the 'optical zoom' notation? I searched a bit and found this one:
optical zoom = maximum focal length / minimum focal length
For example a 18-55mm ...
5
votes
7answers
2k views
How can I visualize or simulate the effect of different focal lengths?
I have seen many camera review sites illustrate the effect of using different focal lengths on the same photograph using frames. There are also similar illustrations to compare different sensors (full ...
9
votes
2answers
2k views
What differences between point and shoot zoom versus DSLR zoom cause the price disparity?
I'm just getting into the world of photography, stepping up from a point-and-shoot. I've just purchased a Nikon D3100 and it should be here in a couple of days.
I've done lots of research, but ...
12
votes
5answers
779 views
Why do we talk about focal-length when frame sizes are different?
I keep seeing people talking about focal-length of lenses without saying how large the frame is. Is there a more sensible way to talk about how much a lens “zooms”?
(I have seen so many adverts ...
12
votes
4answers
3k views
How can a lens like a 18-55mm have more than one focal length?
How can a lens have a range of focal lengths? Shouldn't it be a single number?
Isn't focal length supposed to be fixed for a lens of a particular shape and geometry?
What am I missing?
How many ...
20
votes
4answers
1k views
What is focal length and how does it affect my photos?
What is focal-length? Are focal-length and zoom synonymous? How does the focal length of a photo affect it?
10
votes
3answers
2k views
How does changing focal length affect depth of field?
I'm curious about how my "area of acceptable focus" changes when the focal length of the lens I'm using changes as I zoom (or switch lenses). In particular, I'd like to know how the front & back ...
