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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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3answers
230 views

Which lens/focal length offers the widest viewing angle without too noticable distorions/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 ...
4
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2answers
198 views

Understanding Lenses Focal Length with Converters

I read about APS-C sensors EOS DSLRs, that if the focal length is 300mm and as the image ratio is 1.6 then the 300mm x1.6 = 480mm focal length. So if I add a 1.4x teleconverter to 300mm lens so I ...
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1answer
66 views

Is there an “optimal” background distance when striving for a minimally distracting background?

Let's assume a thin lens and an object O in focus at a distance of dO from the lens. Further, let's assume there's a large out-of-focus background object B at a distance of dB. Now, we know ...
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0answers
206 views

How to get width and height of an image based on distance

I have an app to overlay the images on the camera overlay. But I need to set the width and height of the image based on the user distance. If the distance is, say 8 feet, how can I calculate the width ...
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0answers
66 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 ...
1
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0answers
52 views

Which lens to use for landscapes? [closed]

I bought my Nikon D5200 camera with a 18-55mm f/3.5-5.6G lens as well as a Nikkor 70-300mm f/4-5.6 G lens. I was just wondering if you would be able to tell which lens to use in what situations. Like, ...
4
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5answers
351 views

Unable to get sharp landscape picture

I'm facing often the same kind of trouble when taking landscape pictures... I end up with a picture that could be great but that is totally not sharp ! Example : I set up the maximal focal ...
2
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1answer
177 views

Is 85-135mm really the best for every single kind of face?

They say that focal length around 85-135mm is the best for the head and shoulder kind portraits. I've done some tests myself, I can definitely see the differences. The face is more natural looking ...
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3answers
2k 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) ...
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3answers
1k views

Which is better: a smaller f-number lens or a bigger sensor size?

When choosing a camera, which of the following options would be the best in taking photo in low light situation and cropping photo situation? A smaller f-number lens with a bigger sensor size A ...
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1answer
153 views

How to obtain a subject's measurement from image [duplicate]

I am trying measure real object height from an image. I'm using the below formula real height = (object px height * pixel size * distance)/(focal length) my camera is Canon_EOS_550D, my values are ...
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2answers
133 views

What is the real focal length of the Lytro Illum

According to Lytro, the Illum Light-field camera will have a 30-250mm equivalent focal length with a constant f/2.0 aperture. What is the actual focal length of the camera? Or, What is the sensor ...
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1answer
190 views

Does manual focus carry over to a different aperture, lens or focal length?

This is in the manual focus mode. If I focus my lens so that a certain object is clear and crisp, and then do one of the following, will I have to focus again? Change the aperture Switch to a ...
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3answers
3k views

50mm vs 35mm cropped [duplicate]

For shooting portraits, why is 50mm preferable? For example with an APS-C sensor, why is it not ok to take photos with 35mm equivalent and simply crop them (to 50mm equivalent)? or take photos closer ...
2
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3answers
7k views

What is the relationship of aperture, focal length, and ISO in a SLR?

I was using Nikon digital camera, and recently bought a Canon 550D. I am totally new to SLR. I am not familiar with SLR terms: Aperture, focal length and ISO, and their relation to one another. What ...
3
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3answers
508 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 ...
3
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2answers
1k views

28mm vs. 24mm (wide angle) for selfies?

I know that selfies are an "evil" of this generation, and you're never going to get a good picture when taking one of yourself, let alone when you are unable to compose it bc you can't see the ...
14
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2answers
5k 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 ...
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1answer
59 views

Help to choose lens [duplicate]

I recent got 60d and EF-S 18-55mm Lens and i want to buy 1 more lens specially for product and fashion(portrait) photography... I decided EF50mm f/1.4 USM and EF85mm f/1.8 USM? Which one would be ...
2
votes
3answers
495 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 ...
6
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4answers
738 views

Is f/number more relevant than aperture and/or shutter speed?

I've seen on Flickr that the photographers specify values for four settings about their photos (where exif data is available) - Shutter speed F number ISO Focal Length An example can be found ...
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1answer
491 views

What's the practical difference in an image taken at focal length of 200mm vs 300mm? [duplicate]

I'm confused about the 200mm and the 300mm zoom ranges. I am looking for some examples of the same subject, in order to visualize the difference between 200mm and 300mm focal lengths. I want to ...
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3answers
355 views

How can I take a picture at 50mm with a Finepix s8200?

I have this camera. How do I take a picture at 50mm with zoom lens? Does this camera support zoom lens at 50mm?
1
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1answer
401 views

How to calculate the focal length for old lenses (m42 or m39) mounted on Sony Nex? [duplicate]

As far as I know, it is necessary to multiply the focal length by the crop factor. My Sony Nex 5 has a crop factor = 1.5 For lens Helios 77M-4 1.8/50 focal length will 50 * 1.5 = 75 Is this true for ...
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1answer
7k 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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0answers
118 views

What is the basic relationship between aperture and focal length? [duplicate]

How does a photograph vary with a decrease or increase in aperture as well as focal length?
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3answers
3k 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 ...
2
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3answers
937 views

Is 50-200mm (APS-C) a good zoom range for a single lens for people, buildings, and distant objects?

Assuming I do want to take pictures of things like people, buildings and things further away, but not too far away. Does it sound reasonable to buy a 50-200 mm lens, when just considering the distance ...
0
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1answer
217 views

Is this attempt to make lens measurements and focal lengths more intuitive correct?

I know next to nothing about cameras (other than how to push the shutter button). Up until a few days ago I thought of zoom as simply a multiple (e.g. my Canon S95 has 3 or 5X optical zoom) and had ...
7
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3answers
330 views

Do crop sensors on SLRs changes the depth and flatness of the objects as well? (in comparison to same focal length on full frame sensors)

1- I know different focal lengths change the depth and flatness of an objects in the picture. For examples longer focal lengths make objects appear flatter so they will be appropriate for portraits. ...
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0answers
83 views

How to calculate the zoom power (X factor) for a lens? [duplicate]

Possible Duplicate: How do I convert lens mm to optical zoom times? How can I obtain the "X factor" for a lens? I thought that to get the "X factor" I had to divide the largest focal ...
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3answers
319 views

At what distance from the lens will the image be in focus given a subject distance and focal length? [closed]

I've been trying to figure this one out for more than an hour now and I have no idea how to calculate this... You capture a picture of a tree which is standing 3m away from the camera. The focal ...
2
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1answer
1k views

Can I build my own focal reducer by reversing a teleconverter?

Would it be feasible to reverse a 1.4x teleconverter's optics into a cross-system lens mount adapter & have it function as a focal reducer? For example, like this: Camera hacked adapter ...
1
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2answers
511 views

Which is a better focal length for fashion models on the runway: 50mm or 35mm?

Which is a better focal length for fashion photography: 50mm or 35mm? I have Nikon D5100 and Nikon D7000 and I'm interested specifically for ramp walk.
1
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1answer
1k views

Canon 24-70mm 2.8f - Optimal aperture for sharper pictures

I always have trouble getting sharper images from my 24-70 lens. I have watched numerous YouTube videos to correct this and its improved but not completely corrected. I am going on a trip and don’t ...
0
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1answer
168 views

What focal length and quality of lens do I need to read 15cm high text at 500m away? [duplicate]

I have to photograph 15cm high printed text from 500 meters away. The text has to be human readable in the result. What kind of focal length do I need? Can i compromise, and get a camera with less ...
1
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1answer
276 views

What is a 50mm focal length good for on an APS-C camera?

This is on a Sony NEX, so the 35-mm equivalent focal length is 75mm. What kind of photography is this focal length good for? I shoot low-light, landscapes / cityscapes, and the typical vacation ...
0
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1answer
91 views

Take a photo and print it to show approximate view of a human from a distance?

If I want to take a photo from about 600' away from my front door, and I want it to emulate what a person would see with unmagnified view, what mm would I set my camera lens length AND then what size ...
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2answers
415 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 ...
18
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4answers
538 views

Is there construction-agnostic term for a lens with a long focal length?

Turns out that telephoto refers to a specific construction of a long-focal-length lens, i.e., one where the lens is physically shorter than the focal length. Is there a generic term for referring to ...
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1answer
720 views

Size of the entrance pupil vs size of the 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 ...
3
votes
2answers
558 views

Image size of the Sun / Moon from a telephoto lens

I'm interested in taking a picture of the Sun / Moon using a telephoto lens. For example like this. It would be very helpful for me to know what the approximate image size of the sun / moon would ...
1
vote
5answers
2k views

Keeping two subjects in focus (depth of field)

What is the best way to get two subjects in focus in a portrait (sometimes not at the same distance from the lens)? Obviously, this is a question of depth of field, but I am curious what some of the ...
7
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6answers
1k views
8
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1answer
348 views

Why do certain lenses increase angle of view upon close focus?

I recently picked up a superzoom lens, the Nikon 28-300mm. Although I got it primarily for its versatility, my intuition was that a lens that can do 300mm focal length at 50 cm, as indeed it can, ...
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4answers
1k views

How much does 1 mm get you in a wide-angle lens?

I'm looking at a Canon 17-40 mm wide angle lens, and I don't understand why anyone would buy it. EFS18-55mm II is the standard Canon 18-55 mm lens that DSLRs come with, and it seems almost as ...
14
votes
4answers
6k 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 ...
0
votes
1answer
143 views

What does “focal length multiplier” mean? [duplicate]

I have heard of something called a focal length multiplier, particularly in connection with the size of the image sensor in a camera. What I don't understand is what this is and why ans how it is ...
36
votes
10answers
5k 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 ...
0
votes
2answers
79 views

Finding the point corresponding to a known height in an image

I have an image of a wall taken from a phone camera from a known height h from the ground. Assume that the camera was held perfectly parallel to the wall and that the bottom of the image is perfectly ...