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Focal length is the distance (measured in mm) between the surface of a lens and the focal point, when the lens is focussed at infinity. Smaller focal lengths indicate wide-angle lenses, larger focal lengths indicate a telephoto lens.

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7answers
5k views

What is a normal lens?

I've heard people call 50mm lenses "normal lenses". For a lens to be considered normal, does it have to be exactly 50mm or is there some leeway? Does the normal focal length depend on crop factor of ...
24
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5answers
6k views

Does my crop sensor camera actually turn my lenses into a longer focal length?

So, I mount a 200mm lens on my Canon 450D. It effectively becomes a 320mm lens. Is this the equivalent of 320mm on a full frame camera? That is, from what I've figured out I get an equivalent field of ...
1
vote
2answers
215 views

How to achieve full-frame look/view on a crop-sensor - without changing the lens?

I have a Canon 600D, which is crop-sensor camera. If you're shooting with a Canon EF 50mm, it'll be (50x1.6) = 80mm on a normal full-frame body right? I'm also a street-photography-kinda guy, which I ...
-1
votes
0answers
21 views

How do I get my focal length unstuck? [duplicate]

I need help! My focal length is stuck at 55mm and I can't turn it to any other focal length. Someone please help me.
0
votes
1answer
810 views

Below which focal length are lenses considered to be wide angle?

Focal length is the only factor that decides whether a lens is described as being normal or wide angle. Below which focal length are lenses considered to be wide angle? Is this focal length the same ...
1
vote
3answers
239 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 ...
1
vote
2answers
70 views

Does 4.0-72mm on the lens when equivalent focal length is 24-432mm mean crop factor of 6×?

The Samsung WB250F has 4.0mm-72.0mm printed on its lens, and its 35mm equivalent focal length range is 24mm-432mm. Does that mean it has a 6x crop factor?
9
votes
4answers
343 views

Circular polarizer works great at shorter focal lengths, but significantly degrades the image at longer lengths. Why?

I bought a cheap CP recently to play around with, and noticed an interesting phenomenon: Using it with my 24mm lens on full-frame, images turn out tack-sharp - there is hardly any difference in ...
11
votes
2answers
6k views

Why is depth of field affected by focal length?

As the focal length decreases, the depth of field increases as well. Why is this? I'm not so much interested in a physics lesson as I am interested in a simple, down-to-earth explanation.
6
votes
5answers
4k views

Is an EF 50mm f/1.4 the same as 50mm with an EF-S lens on a Canon 550D?

I have a Canon 550D with the standard 18-55mm kit lens. The 550D has a 1.6× crop factor. My question is very simple but whenever I've asked before (Yahoo Answers) I always got overly-complicated ...
12
votes
3answers
1k 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 ...
0
votes
1answer
216 views

How can I tell what focal length a zoom lens was set to for a photo of the moon?

It appears that neither the Sony 55-210 mm f/4.5-6.3 nor the Canon EF-S 55–250mm f/4–5.6 reports the actual focal length to the camera: both cameras' metadata show the lens but report the focal length ...
6
votes
1answer
227 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 ...
4
votes
5answers
431 views

What focal length is used in photos that both model is zoomed in and the background is open

It is easier to explain my question just by a sample photo from Lyndsey Adler: See the models are so big in the photo and still that big RV is also in the image. What focal length do I need for a ...
6
votes
4answers
411 views

How is actual focal length greater than focal range of lens?

This image (not shot by me) is shot using 70-300mm f/4.5-5.6 lens, but the EXIF shows the focal length to be 302 mm. How is it possible to be shot at a focal length (302 mm) greater than the ...
0
votes
2answers
50 views

Where is the image sensor located in a camera with a fixed-focus lens?

I am working on some research on the Kinect for XBOX One. I am looking into the depth measurements of the device. I have read that the depth values are calculated from the devices focal plane. So i ...
5
votes
6answers
302 views

What do the mm numbers on lenses mean?

I'm confused about lenses and numbers. Why are some lenses ex. 50mm-300mm Different sizes? Some lenses with the same mm numbers are huge and some are small... What's the difference? Also the prices ...
1
vote
3answers
4k views

Is the formula for object image size given focal length, etc. independent of sensor size?

I am trying to figure out how big an object of, say, 50cm height at 100m distance and 600mm focal length would appear on a camera's sensor. The ubiquitous formula object size in image = focal length ...
0
votes
6answers
130 views

What is the shortest focal length before a black ring appears?

I know it depends on brand to brand and model to model, but in general terms, what is the shortest focal length I can have before the black zone (A) starts to form, or it is barely noticeable? (B) ...
4
votes
4answers
637 views

Why do two zoom lenses set to 200mm on the same camera produce different fields of view?

I've been testing out a Nikon 18-200mm F3.5-5.6 against a Nikon 55-300mm F4.5-5.6 I took two pictures of a door knob from an equal distance of about 3 meters away with the same Nikon d7100 DX camera ...
37
votes
11answers
6k views

What is crop factor and how does it relate to focal length?

I'm reading that a 50mm lens is recommended as a first prime lens for DSLR owners as it's supposed to give a 'natural' perspective, but when used on (most) DSLRs, the view is cropped, as if you were ...
1
vote
5answers
3k views

Why image at 400mm is LARGER THAN DOUBLE of image at 200mm? (according to lens formula)

Like most of us, I thought it was yes. Until I really look into the Lens Equation: (1/subject distance) + (1/image distance) = (1/focal length) ...
4
votes
4answers
155 views

Which focal length lens generally has the sharpest lens? 24, 35, 50 or 85?

Context I realize that the above four focal lengths lend to having a different perspective that make them all unique. It might be possible to use one as the other but that isn't always true with the ...
3
votes
1answer
77 views

General rules when compression in the background looks good (like with longer focal lengths)?

Is there any general set of rules or guidelines on when would the background compression generated by a long focal length look good in a picture? Example : in a headshot, I really like the background ...
2
votes
1answer
69 views

Possible to lock focal length on zoom lens? (SELP1650)

(This could turn out to be a bone, practical, product-specific query, but this is the internet so the worst that could happen is a 0 rather than a 1.) Anyhoo: is it possible to lock a zoomable lens ...
2
votes
2answers
117 views

Do I need the 18-55mm lens that comes with the camera, or should I instead get a 55-250mm lens?

I'm a novice so don't know whether I need the 18-55mm lens that comes standard with the Canon EOS Rebel T6i or should I instead get the 55-250 mm lens - or both? I'll be using the camera primarily ...
5
votes
6answers
4k views

What is a good focal length for street photography?

With a long lens you don´t disturb people but you are left "out of the scene", while with a short focal lens you are "inside the scene" but you may disturb people. What is a better alternative for ...
0
votes
2answers
113 views

Effective focal length of kit 16-50mm lens on A6000 (APS-C 1.5x crop factor) [duplicate]

This is likely a tedious question for you guys but, as a camera noob, I'm miffed, so please bear with me. I have a: Sony A6000 (APS-C 1.5x crop sensor). With kit lens: SELP1650 lens (16-50mm) So, ...
38
votes
11answers
15k views

Which focal-length lens is usually used for portrait photography, and why?

What focal length or range of focal lengths are usually used for portraits? What is used by professionals? Why would one select a certain focal length? What are the advantages and disadvantages of ...
5
votes
4answers
450 views

How do manufacturers come up with focal lengths for lenses?

There are a lot of lenses for each camera, and I understand that each lens caters to a different use case, but my question is on how they arrive at the specific focal length numbers. For example, ...
10
votes
2answers
4k views

How can a lens with a single focal length focus on more than one plane?

By definition, a prime lens is a fixed lens system with a fixed focal length. Then, simple physics tells us that it should be able to focus only on one plane (at a fixed distance) in front of it. But ...
2
votes
2answers
234 views

Panasonic Lumix FZ1000 - How does it compare to binocular magnification?

I know almost nothing about photography. But I am interested in learning. My dad just purchased a Panasonic Lumix FZ1000. I own a pair of Leica 10x50 binoculars. I asked him how the maximum zoom or ...
3
votes
1answer
85 views

Which lens size will generate more detail for equivalent field-of-views in an image snapshot?

We are getting ready to purchase a 3 megapixel IP camera. It comes with either a 4mm or 6mm lens. We will only be using the camera for still image snapshots on a specified interval. Basically, it's an ...
2
votes
4answers
338 views

Are wide angle lenses suitable for portraiture of children?

Wide angle lens tend to make faces more "chubby" than they appear otherwise, and are therefore not used often for portraits, unless the landscape is an important part of the frame. I'm curious as to ...
1
vote
3answers
191 views

What focal length is recommended for photography for social media, like groups of people in weddings?

I want to get a lens for social photography (groups of people in weddings, or a close up for a bride). What focal length range would be recommendable? Also would it be good to get a wide angle lens ...
0
votes
1answer
96 views

What's the ranges of ratios of Focal Length to Sensor Height to approximate a human eye's view? [duplicate]

Given this formula for calculating the distance to an object as long as you have a picture of the object and know the actual height of the object... distance to object (mm) = focal length (mm) * real ...
15
votes
2answers
2k views

Why does a 50mm lens appear to give a human perspective, rather than a normal lens?

I grew accustomed to the notion that what one sees through a normal lens equates (or is close to) what can be seen with the naked eye (although that is not the "pure" definition of a normal lens, ...
2
votes
3answers
187 views

Is the Canon 70-200mm or 24-70mm better for convention photos? [closed]

I've decided I want to upgrade to a better lens, but I'm really torn between the Canon EF 70-200mm f/2.8L IS II USM and the EF 24-70mm f/2.8L II USM. I like to take convention photos, where space is ...
2
votes
2answers
195 views

How do you calculate the focal multiplier of a non-full frame camera?

I'm currently using a Sony RX100 Mark 3 camera and want to buy a Canon 6D + 24-105 F4 L lens from an online retailer, which is not in my country. (before continuing I'd like to state that there are ...
41
votes
9answers
20k views

Do professionals really never use a 24-70 lens?

I was reading lens reviews on the Rockwell site — mostly because it came up as first result in Google search — and he was saying professionals don't need and don't use mid-range zoom lenses like 24-70 ...
2
votes
3answers
171 views

Why isn't my computation of the actual size of an object in a photograph matching the expected value?

Let's say I have a full frame camera (Sony A7) with a 50 mm lens (Canon FDn 50mm f/1.4) mounted on it. At a given object (a plane) distance I should be able to compute the size of the image in real ...
4
votes
3answers
321 views

Does focal length change when I adjust the focus? [duplicate]

When I adjust the focus of my camera, in general, does this affect the focal length? I have heard that it does.
6
votes
6answers
6k views

Why do Canon EF and EF-S lenses exhibit the same crop factor?

I have a Canon 7D, which has a crop factor of 1.6x. When using a Canon EF-S lens I get the focal length stated on the lens, when using a Canon EF lens I get the focal length times 1.6 when used on ...
1
vote
4answers
32k views

So my iPhone 6 camera lens is as wide as my full frame 35mm DSLR lens?

I am trying to understand what is the deal with "full-frame" and what difference it makes, so did a silly test: I sat at my bed and aligned the iPhone 6 camera with the door of the room and took a ...
3
votes
2answers
136 views

55mm on an 18-55 lens versus 55mm on a 55-250mm lens

I have two canon kit lenses which came with my 1100D. While experimenting casually with my lenses, I came across something that I find peculiar. When I am focused at an object at a certain distance on ...
0
votes
3answers
155 views

Do lens hoods need to be matched to focal length?

Is it true that not all generic lens hoods work on all lenses (provided the filter diameter matches, of course)? I read that the focal length plays a role in it - but I cannot find such readings on ...
16
votes
9answers
52k views

What lens focal length most closely resembles the perspective of the human eye?

For example, if I have a lens that is 16mm-50mm, which focal length would be the closest to the human eye's view? (I don't have a camera yet, so I'm just curious.) Would 50mm be more zoomed in than ...
4
votes
1answer
229 views

What are the advantages and disadvantages of zoom lenses with a wide range of focal lengths? [duplicate]

Are there some disadvantages of a zoom-lens with wide range focal length compare to a lens with narrow range both having the same max. aperture? For example, if we have two lenses: Sigma 18-55mm f4 ...
0
votes
1answer
39 views

Focal length of the sony DSC-H20 [closed]

I am working in finding the distance of the objects in a video taken using a Sony Camera model DSC-H20 and suppose that any lens or zoom distortions were applied. In order to know the position I need ...
0
votes
6answers
187 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 ...