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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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102 views

How can I increase the flange focal distance (back focal length) of DSLR lens?

I am working on a custom setup where I am using a DSLR lens (Canon 50mm f/1.8) to project an image onto an image sensor (image plane). For my application, I require a very large distance between the ...
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4answers
67 views

Calculation for getting dimension of object in image not working

I am trying to calculate the dimensions of an object in an image. This is a sample image I took to get height of blue shirt: I am following the math from this page with sastanin's answer. How do I ...
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2answers
65 views

How to determine film size from smartphone image exif data?

I took an image from my phone and got its exif data below. It was a samsung note 4, which uses a 35mm film size (24x36) with a 43.27 diagonal. But what I am trying to figure out is the sensor diagonal ...
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4answers
77k views

How do I calculate the distance of an object in a photo?

If I took a picture of a windmill on the horizon — given that I know the sensor size and the focal length of the lens and other factors to do with the shot — could I calculate how far away an object ...
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3answers
57 views

When should ¹/EFL become ¹/(2 × EFL) to avoid camera shake

Where is the boundary when I should set my shutter speed to ¹ / (2 × EFL) instead of ¹ / EFL to avoid camera shake? (EFL = Equivalent 35mm Focal Length). Let's assume the lens has no image ...
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2answers
73 views

Does focal length affect coordinate estimation?

I am using a webcam mounted on the ceiling to track some markers. I measured the area on the ground that the webcam is able to see, it is roughly 2.61m x 1.46m. The output of the coordinates right in ...
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3answers
5k views

How do zoom, magnification, and focal length relate?

Zoom lenses and cameras with superzooms are often sold with a times ("×") zoom number — like a 12x zoom or 30x zoom. The question How do I convert lens focal length (mm) to x-times optical zoom? ...
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2answers
94 views

Will stepping back and using an FX lens on a DX body get the same “look” as the same lens on an FX body?

Using 85mm as an example, how can I get the same "85mm look" (shot on a FX camera with an 85mm FX lens) on a DX camera with the same 85mm FX lens?? I know a 58mm FX lens (87mm DX equiv), shot from ...
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4answers
418 views

Does being a Macro lens but on a shorter focal length affect taking a tight portrait photo?

I want to do some beauty portraits. Some of my shots will be from waist up, some of them will be tighter. For example just the face and nothing else in the frame OR a little going back to get the ...
2
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1answer
85 views

Will a focal length reducer help me image deep sky objects using an 8" newtonian telescope?

Will a 0.5x focal length reducer help me to reduce the exposure time if I am imaging deep sky objects? I'm using a 1200mm focal length optical tube (f/6), a 32mm super view telephoto extension ...
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5answers
12k views

What software can show my most frequently used focal length?

Many people recommend a focal length of 35mm, 50mm, and sometimes even 85mm and upwards for those interested in purchasing a prime lens. I, however, would like to figure out what focal length(s) I use ...
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3answers
177 views

What lens will get the whole body in the picture for street fashion photography?

I'm looking for a lens for fashion street photography which covers all the body in the pic. Do you recommend the Nikon 50mm 1.8d or Nikon 35mm f / 1.8G for my D3300 camera body? (I don't have the ...
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1answer
10k views

Why does my aperture setting change as I zoom on my DSLR kit lens?

I am new to the photography field, there are few things 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 ...
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1answer
1k views

Does focal length affect diffraction, in addition to aperture?

The reason I ask is that f/18 on a 24mm lens = 1.5mm, and f/18 on a 180mm lens = 10mm. I thought diffraction is due to the small physical size of the aperture, rather than the f-ratio, yet I only ever ...
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2answers
591 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 ...
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2answers
453 views

Does focus breathing make a lens slower when close focusing?

I've heard that focal length of some lenses will become noticeably longer when focusing to a close distance, an effect called "focus breathing". Since f-number is focal length divided by diameter of ...
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4answers
29k views

How do people shoot very large moon views?

I see pictures of the moon that looks like it is very close to the earth; I am wondering whether they are real or is there a trick to show the moon that big? Here is an example: http://www....
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5answers
2k views
2
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1answer
118 views

Why do DPReview's charts show the G7X II as having an aperture around f/8?

I have a Canon G7X II camera, which has a 24-100mm f/1.8-2.8 lens. Why does DPReview's chart show it having an aperture of around f/8 at a focal length of 100mm?
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4answers
8k views

Does using a lens adapter change focal length?

Does using a lens adapter change the field of view? I recently bought a Sony NEX-5, an extra Minolta MD 50mm 1.7/f lens and a MD to E-mount adapter and I was wondering, as the adapter increases the ...
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2answers
113 views

What is the relationship between field of view and focal length for fisheye?

What is the relationship between the focal length and field of view for an equal-area ("equisolid") projection fisheye lens? Alternatively, what is the relationship between the 180-degree image ...
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1answer
33 views

How far do I need to extend bellows to achieve particular minimum focal length [duplicate]

If I have a 200mm lens, and want to focus at, say, 450mm from the camera, two questions: can I (do I need to) use bellows to achieve this? is there a formula for how to work out how much extension I ...
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2answers
4k views

Why doesn't the background become blurred when I change the aperture on my Fujifilm S4000?

I am sorry if my question is too naive, but I am a complete beginner in photography, and I think I still need to understand well what aperture is. I have a Fujifilm S4000 camera, and I know I can't do ...
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3answers
212 views

Why are crop lenses indicated with focal lengths they don't have [duplicate]

If we will use crop lenses only on crop bodies, why do we all crop lenses for example "10mm" when they are actually "16mm" (with a crop factor of 1.6 in this case)? Edit: I am familiar with the ...
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1answer
114 views

How to overlay the image scaling based on the user distance & focal length

I'm overlaying images on the cameraView and based on the user input of room width & height. The images are displaying proportionally to width & height ratio. but i need to overlay the images ...
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2answers
53 views

Focus change after switch off camera?

I am using a zoom lens. The focal length is adjusted to 70 mm with manual focus. I then switch off the camera. Will the focus change after i re-turn on the camera? Noted that focal length and zoom ...
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4answers
147 views

What lens will let me take a photo of a bird high up in a tree?

What lens would work for a canon 6D to take up close photos of birds far away in the trees? My Canon 100mm-400mm lens just doesn't get that close.
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3answers
103 views

Difference between focal point and distance away from object? [duplicate]

I have a macro lens for the camera on my phone. I want to calculate the magnification of the lens because the one i purchased does not state it. I've found this guide which states the mathematical ...
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6answers
3k views

Is there a difference between taking a far shot on a 50mm lens and a close shot on a 35mm lens?

I am looking for a prime lens to pick up, and I'm wondering if there is any difference between 35mm and 50mm in terms of the end product if I just stand back more with the 50mm. I use the Sony a6000 ...
0
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3answers
306 views

Which lens/focal length offers the widest viewing angle without too noticable distortion/fish-eye-effect?

I am looking for a lens for my Sony Alpha 77 (APS-C), which gets me an as wide as possible viewing angle, but I also hate that fisheye effect one gets from using too low of a focal length. About where ...
12
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2answers
1k views

Does a crop sensor affect closest focusing distance? Why does it not affect focal length in EXIF data?

Since I am considering to buy the Nikkor 105mm micro VR, I wondered if the cropped sensor does affect the closest focusing distance of 0.31m? Thinking about this, the following additional (and ...
41
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12answers
7k 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 ...
2
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5answers
794 views

How can I explain focal length to someone who isn't into photography?

Context So my friends and family are curious about how far my lens can reach. I usually explain with focal length and show them a few pictures. Question Is there any easier way to explain what ...
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1answer
45 views

focal length 300mm on dx camera + 2X TC [duplicate]

I saw nikon Nikon AF 70-300mm f/4.0-5.6G which works on both DX and FX sensor camera. I have Nikon D3300 which have DX sensor. As lens works on FX sensor if we use this lense on DX camera what would ...
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4answers
270 views

Does an APS-C lens label itself with effective or true focal length? [duplicate]

I'm not sure if I've phrased this correctly, but I've just purchased two prime lenses: Nikkor 50mm f1.8/G (FX) Nikkor 35mm f1.8/G (DX) I know that the effective focal length of the 50mm FX lens ...
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5answers
51k 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 ...
0
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2answers
139 views

Shouldn't the diameter of the moon with a 600mm lens be double what it is with a 300mm lens?

I used a 300 mm lens and recently bought a 600 mm lens, thinking that the area in the frame with the 600 mm lens will be exactly half of the area covered by the 300 mm lens. Practically I am not ...
0
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2answers
173 views

35mm DX prime lense on dx crop sensor(nikon d3300) [duplicate]

I have Nikon D3300 DSLR. I'm confused with 35mm and 50mm prime lenses on FX and DX cameras. Somewhere I read that if a 35mm prime lens is used on a FX camera the focal length is equivalent to around ...
11
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4answers
5k 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 ...
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6answers
5k 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 ...
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1answer
43 views
21
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5answers
1k views

What is the shape of the focal plane?

This is something I just realised I don't entirely know the answer to, so I'm going to ask it here as I think it's interesting. In most non-scientific writing on depth of field, diagrams generally ...
45
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7answers
198k views

How do I convert lens focal length (mm) to x-times optical zoom?

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 ...
6
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6answers
7k views

Why do Full Frame lenses and crop body lenses exhibit the same crop factor when used on a crop body camera?

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 ...
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1answer
265 views

How does focal length determine lens quality? [duplicate]

What does an 18 - 50 mm lens mean? Are those numbers the first focal length and second focal length? How do you use this parameter to judge what kind of lens to buy? Does more equal better?
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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 ...
26
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5answers
8k 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 ...
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2answers
426 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 ...
0
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1answer
895 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 ...
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3answers
486 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 ...