Linked Questions

1
vote
1answer
848 views

How do lenses focus? (and zoom?) [duplicate]

My understanding of focal length is that it is the distance from the lens to the sensor; in my observations: higher focal lengths make for longer lens. Then I started thinking about how a lens ...
0
votes
1answer
705 views

camera mobile phone takes pictures at constant focal length if 3.5 mm.supposed to have autofocus and touchfocus [duplicate]

This is a cheap Chinese landvo l200 Android mtk65xx mobile The onlything it keeps Changing is IS0 from 150 to 800 + And exposure time I wondered how can it autofocus and touch Focus when it keeps ...
1
vote
4answers
402 views

How do fixed lenses “focus” on things at different distances? [duplicate]

I'm trying to understand depth of field and I'm struggling. If I'm playing with a 50mm fixed lens, and I alter its focus using the little ring around the lens, what is actually changing in terms of ...
0
votes
1answer
422 views

How do prime lens allow variance of focal length when focusing? [duplicate]

If the definition of prime lens says that their focal length is fixed, then how come you can still alter the focal length when focusing? (either MF or AF)
29
votes
3answers
8k views

Does changing the focal length change focus?

When using manual focus or back focus on D60, I sometimes zoom in the lens, set the focus, and then zoom out. Does changing the focal length (zooming out), also change the focus? In case the answer ...
26
votes
3answers
11k views

How can a 18-55mm lens focus on objects beyond 55mm?

I guess this is a total noob question, but doesn't 18-55mm mean that it can focus only up to 55mm?
14
votes
3answers
17k views

What is the technical difference between focus and zooming?

This may look like a silly question but I don't know what the difference between zooming and focusing is. Zooming in will usually let me have fewer subjects in the scene while zooming out will allow ...
8
votes
2answers
3k 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 ...
9
votes
2answers
6k views

How does ground glass work when focussing?

To use ground glass, I turn the focusing ring on my lens until the image becomes clear on the glass. But what is it about the glass that makes this work? What are the physics involved?
0
votes
3answers
848 views

Why doesn't the focal length in EXIF change when I manually focus my DSLR?

I tried to take several pictures with a DSLR ( Nikon D3200 - 18 to 55mm zoom lens) with manual focus mode. I changed the manual focus randomly and clicked several pictures one after another. I was ...
1
vote
2answers
1k views

How do I calculate the depth of field of cameras on mobile phones with auto focus?

I just hope to learn the relationship between depth of field (DOF) with the distance on my mobile phone. When I capture one cup with the distance about 20cm from my phone, what 's the DOF? When I ...
2
votes
2answers
351 views

How does (auto-/manual-)focus changing work?

I know when I change focal length of a zoom lens the physical length of it is changed. It's understandable: the optical parameters of the lens were changed. But what is going on when (auto-/manual-)...