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

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Are there specific use-cases in mind that make the 70-200 F2.8 worth its weight/size?

I've been looking to upgrade my Mark iii's kit lens, and am comparing lens strategies. The 70-200mm canon F2.8 seems like an enduring and very popular lens. After holding one, i am left wondering why? ...
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3answers
2k views

50mm lens=75mm on DX camera? [duplicate]

I'm looking for a 50mm lens for my nikon d3100 and I just came across an AF-S 50mm f/1.8G lens and it says in the description that if it's used on a DX camera, the angle of view is going to be 75mm. I ...
4
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1answer
232 views

What factor determines the largest usable sensor size with a certain lens?

Reading this excellent answer about field of view, focal length and sensor size a new question came to mind. From the drawn diagrams it is clearly visible that for the same focal length an increase ...
15
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1answer
1k 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, ...
16
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5answers
6k views

What focal length gives a “normal” field-of-view on APS-C cameras?

I wish to purchase a "standard angle-of-view" prime lens for my Canon Rebel, which has an APS-C sized sensor. Various articles note that the popular "nifty 50mm" lenses are a little too much of a ...
5
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2answers
920 views

Is there a difference between using a telephoto or wide-angle lens for portraits? [duplicate]

Possible Duplicate: Which focal-length lens is usually used for portrait photography, and why? Assuming a similar aperture, what difference would you see using a 50mm, 85mm, or telephoto ...
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2answers
1k views

What is the benefit of a dedicated wide angle zoom vs a superzoom?

I am considering buying a Sigma 10-20 mm F3.5 wide angle lens for my canon 550D, but not sure what the benefit would be compared to using the wide angle end of my existing Sigma F3.5-6.3 18-250 mm ...
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1answer
297 views

Why 5-50x focal length for autofocus micro-adjustment?

When we do an AutoFocus Micro Adjustment session, the general opinion is to set the focusing target at 25 x focal length (or somewhere in the range of 5-50 x focal length). Why is so? What happens if ...
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3answers
493 views

Is it possible to calculate focal length if you know the aperture?

I need focal length (for my IA homework), but I didn't know that in real world I would only get the aperture. Ok, my camera is an Olympus X-21, and manual says: -----Olympus lens: 6.3 to 18.9 mm, ...
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3answers
904 views

How much distance should one move so that a shot that can be framed at xx mm be framed at yy mm?

Is there a website / app that will tell you approximately how much distance a person should move so that they are able to frame the same shot at different focal lengths? Say for example, I'm ...
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3answers
434 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 ...
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3answers
660 views

Must I allow for crop factor in the viewfinder when shooting with a Nikon DX format camera?

Will a Nikon D5100 (dx format) viewfinder show me what the captured image will be, or do I need to allow for "crop" factor? Will that depend on/alter with using a DX lens or an FX lens? I don't have ...
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2answers
2k views

When I use FX lenses on a DX camera, does the focal length or minimum aperture change?

If I put a Nikkor 35mm f/2 FX lens on a DX camera, is it still 35mm f/2, or has the effective focal length or minimum aperture changed, because it is being used on a smaller format than what it was ...
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2answers
232 views

What does different focal length offer me?

I have a beginner photographer and I have spent a lot of time learning the basics (exposures, lenses, focal lengths, crop factor etc). It's all good except I'm not so sure when I need to buy lenses of ...
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2answers
1k views

How to calculate the size of the image circle at infinity focus?

How can I determine the diameter of the image circle (i.e. the diagonal size of CCD required to fully utilise a telescope's optics) at near-infinity focus? I have looked around online and found this ...
8
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3answers
940 views

How can a 24-70mm and a 10-22mm both be “wide angle” lenses?

I've been looking at a 10-22mm lens for my Canon T2i. I've also come across some other "wide angle" lenses, like the Sigma 24-70mm F2.8. I don't understand how a wide angle lens can have such high ...
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3answers
211 views

What is the difference between shooting with different (but similar in quality) lenses at same focal length?

What are the theoretical and/or practical differences between shooting with different lenses at same focal length? For example, if we are shooting with a 24-70mm f/2.8 lens at 70mm focal length vs ...
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5answers
4k views

Can I use my APS-C kit lens as a reference for choosing between 50mm or 35mm prime lenses?

I'm looking at getting a second lens in addition to my Nikon D7000's kit lens. I want to know if it's possible to use my 18m-105mm kit lens to get an idea of the focal length for a 35mm lens vs. a 50 ...
4
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2answers
1k 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 ...
4
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1answer
5k views

How do I find a camera's focal length in pixels?

I am working on camera pose estimation. For this, I need the focal length of my smartphone camera in pixels. (My phone is HTC Wildfire S, with Android 2.3).
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1answer
162 views

Where exactly would the focal length of a lens in the ray diagram fall?

If a lens is specified as (EF 50mm f/1.8), where exactly is the 50mm distance if I were to show it in a ray diagram? Considering that a lens is made up of multiple elements, I could not find a ...
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2answers
943 views

What are the technical camera specs for the HTC Wildfire S?

I am trying to do some CGI manipulations on pictures I've taken. In order to fake reality with some 3D object inserted in the picture, I need some information to configure my virtual camera so it can ...
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1answer
253 views

EOS M focal length conversion to cropped frame and full frame camera

I am thinking about EOS M .. it looks appealing to me ... especially for Hiking .. the thing i want to know is if I use my 18-55mm Canon lens (that normally come with 550D, 600D series) on EOS M with ...
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3answers
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What does it really mean that telephoto lenses “flatten” scenes?

This is another perspective distortion question. I understand that perspective distortion is primarily a function of capture and viewing distance, but I am still working on fully understanding the ...
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1answer
100 views

How to calculate the new field of view from an existent one?

I have a photo having H x W (height x weight) pixels and I know, based on the EXIF, that it was shot at F1 focal length. How many pixels I must crop (or add) in order to see how it would be the photo ...
3
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2answers
4k 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 ...
3
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1answer
1k views

Taking pictures with fixed/full focus camera

I have got a fixed focus, 5 MP camera with 3.3mm focal length (not sure what it means) on my phone. I want to know what's the best way to take pictures with since it's missing auto-focus feature. Is ...
5
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1answer
1k 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.
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4answers
1k views

What does 'Equivalent to 1.6x the focal length of the lens' mean?

In the specifications of Canon 550D, about the lens the following is mentioned LENS Lens Mount EF/EF-S Focal Length Equivalent to 1.6x the focal length of the lens Now this is really ...
8
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2answers
2k views

Does a Nikon DX lens on a FX camera get subjected to the 1.5X crop factor?

My friend has a Nikon 35mm DX lens that I want to use on my FX camera. If I use his lens on my camera in DX mode, does the effective focal length of the lens become 35mm * 1.5 = 52.5mm, or does it ...
4
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2answers
4k 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 ...
2
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2answers
1k views

Zoom Lens and Prime Lens Photo Comparison

Are there any examples comparing the picture quality of prime lenses and zoom lenses with the same scene and shot at the same focal length? I have not seen anything that shows me why a prime is better ...
4
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2answers
3k 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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1answer
421 views

Does the X-Pro 1's “Lens Focal Length Setting” do anything with automatic lenses?

In the X-Pro 1's custom menu, one of the options is Focal Length Setting. The manual says: FOCAL LENGTH SETTING (Defaults to 50mm) Enter lens focal length when using a lens that does not ...
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3answers
1k views

How does using a lens with some focal length on a full frame camera differ from using a lens with “equivalent” focal lens on a crop camera?

As an example, a 35mm lens on a crop body (such as Nikon DX) is said to be "equivalent" to a 50mm lens on a full frame body. Equivalent here means that they will have the same field of view, but what ...
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4answers
2k views

When would one choose a 50mm f/1.4 over 85mm f/1.8 (or vice versa) for portraits?

Say you are using a crop body, and you have both 50mm/1.4 USM and 85mm/1.8 USM lens in your bag. Now, you want to take a portrait where there is adequate light and space, and you have decided to take ...
6
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2answers
443 views

Can I get better image quality with a higher focal length or by cropping an image from a sharper lens?

Two well known ways to get better image quality are to use a sharper lens, and to zoom in to fill the frame (as opposed to zooming out and cropping in post). Sometimes there is a give and take between ...
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4answers
3k 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?
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3answers
1k views

Does the shutter speed and focal length rule of thumb apply to cropped sensor cameras?

So, the rule of thumb for shutter speed is that it shouldn't be less than 1 / focal length. Well, that's straight forward on full frame cameras, but what about cropped sensor cameras? Is it going to ...
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1answer
1k views
12
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3answers
2k views

What is the reference point that the focal length of a lens is calculated from?

I understand the idea of a focal length for a single lens, i e the distance from the lens to the point at which parallel rays of light converge. However, in the case of a photographic lens with ...
2
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2answers
510 views

Why are the area of aperture, focal length, and amount of light specified in these terms?

So I'm looking at the wikipedia article on Aperture, and I'm a bit confused. I understand aperture to be the diameter of the hole that lets light in. In the article, someone states that The ...
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3answers
3k views

What does the millimeter measurement of a macro lens mean?

I understand that the millimeter measurement on a lens is, for lack of a better term, how far it can "zoom" in or out, but what about macro lenses? What does the millimeter measurement signify? How ...
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3answers
935 views

How to compare the focal length of a 50mm prime lens with the default lens of a point and shoot camera?

To imagine the 50mm focal length of a prime lens 1.4F, can I simply zoom the lens of my point and shoot camera up to 50mm? Will both the focal lengths be same? Any other way to imagine the focal ...
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2answers
2k views

DX 35mm vs FX 50mm

Will the picture taken from AF-S DX NIKKOR 35mm f/1.8G and AF-NIKKOR 50mm f/1.8G be one and the same because of the DX and FX format??
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2answers
1k views

How far away can I be and still get a sharp subject with a 100mm lens?

If I have a 100mm lens, how far away can I shoot the subject? If I am shooting basketball, how far can I shoot the subject and still get a sharp picture?
4
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3answers
2k views

What is the meaning of single focal length?

The Nikon AF-S DX Nikkor 35mm f/1.8G is described as a single focal length lens: http://www.nikon.co.in/products.php?categoryid=1014. What does that mean? What are its disadvantages as compared to ...
8
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6answers
6k views

How do I get the 'equivalent' focal length for a DSLR lens for my camera?

On my Nikon D3000, how do I figure the focal length equivalence? In other words, if I want a lens that is just like a 50mm lens on a 35mm film SLR, I need to multiply by a factor. What is the factor, ...
12
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4answers
352 views

What is it called when an object appears to be the same size with the eye and through the camera viewfinder?

I have a Canon 18-135 lens. I am looking into the camera viewfinder with my right eye and not through the viewfinder with my left. I start from 18mm and keep zooming in till I see a particular object ...
24
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4answers
4k 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 ...