Field of View on Crop-Factor Cameras

[psubrahmanyam]

Hi

I recently made Photgraphy as hobby and I have been going through several forums and discussions on DSLR and lens compatability. I could not find a clear answer on the following. May be there is a discussion or article , I might have missed.

I have Canon XS body and recently purchased EF-S 17-55MM Lens. What is the field of view for this lens on Cropped bodies ?.

I know if it is a EF lens , then the field of view on Cropped bodies 17*1.6 and 55 *1.6

Is it same even if it is a EF-S lens?

Thanks and regards

Subra

[jiro]

I'm not an optics expert but I think your idea sounds good to me. Mine crops at 1.5X so my Nikon 18-70mm lens works like a 27 - 105mm lens on my Nikon D70. May I ask why are you so interested on the actual field of view of your lens?

[psubrahmanyam]

I dont know much about Nikon lens. Canon makes two kinds of Lens

1. EF Lens can be used on Croped bodies and Full bodies like 5D.
2. EF-S Lens can be used only on Cropped bodies like XS, XSI, 10D, 20D etc.

Curious to know , EF-S lenses also have the same filed of view like EF lenses when used on Cropped bodies.

[jiro]

OK. Perhaps this link can help you: http://www.the-digital-picture.com/C...op-Factor.aspx

[psubrahmanyam]

I could not get a clear answer even after reading the article.

Any straight answer from the experts ?

[Black Pearl]

First off the numbers you are quoting are the focal length of the lens and not the field of view as such these are the actual, correct numbers regardless of the body you then put it on. Should you put it on a camera body that has a small sensor than the image size from a 35mm negative then you need to multiply the focal length by the crop factor (Nikon/Sony/Pentax - 1.5x....Canon - 1.6x....Sigma - 1.7x....Panasonic/Olympus - 2x) to get the equivalent focal length in 35mm (Full Frame sensor) terms.

A quick note - you lens will only fit onto a Canon body with a cropped sensor as the lens extends into the body a little and would snag against the larger mirror of a FF sensored body.

Now to Field of View.

This is the angle of view the lens can capture - yours is listed here - http://www.canon.co.uk/For%5FHome/Pr...x.aspx?specs=1 - and again it is fixed physical characteristic of the lens.

[revi]

I could not get a clear answer even after reading the article.

Any straight answer from the experts ?

A citation from the article Jiro provided:

I say "Canon EF Lens" because Canon EF-S Lenses are made specifically for the 1.6x FOVCF DSLR bodies (but still require the same FOVCF to be applied as the standard Canon EF Lenses to get the equivalent focal length comparison).

(emphasis added by me; FOVCF stands for Field Of View Crop Factor)

That should answer your question, I'd think...

[Black Pearl]

Focal Length:

The focal length of an optical system is a measure of how strongly the system converges (focuses) or diverges (defocuses) light. For an optical system in air, it is the distance over which initially collimated rays are brought to a focus. A system with a shorter focal length has greater optical power than one with a long focal length; that is, it bends the rays more strongly, bringing them to a focus in a shorter distance.

Field of View:

The field of view (also field of vision, abbreviated FOV) is the (angular or linear or areal) extent of the observable world that is seen at any given moment.

Angle of View:

In photography, angle of view describes the angular extent of a given scene that is imaged by a camera. It is used interchangeably with the more general term field of view.

[Colin Southern]

Straight answer: EF-S lenses are labeled in 35mm Equivalent focal lengths, so an EF200mm lens will have the same field of view on a crop-factor camera as an EF-S200mm lens on the same camera.

BOTH lenses on a crop-factor camera will have a narrower field of view than the same two lenses on a full frame camera.

Does this help?

[Black Pearl]

BOTH lenses on a crop-factor camera will have a narrower field of view than the same two lenses on a full frame camera.

Both lenses on a crop-factor camera will appear to have a narrower field of view than the same two lenses on a full frame camera.

The lenses will produce exactly the same angle of view regardless of what they are put on as this is a fixed, physical characteristic of the design. On a cropped sensor camera you are simply using a smaller part of the imaging circle so the angle of view will appear narrower......I'm not helping to make it clear and simple am I?

[tclune]

A useful set of calculators for this sort of thing can be found here: http://www.tawbaware.com/maxlyons/calc.htm FWIW

[Colin Southern]

I'm not helping to make it clear and simple am I?

Um, No

Quite correct in all you say of course, but often it's less confusing for folks to just think of what the net result "is" (eg CF being an effective focal length multiplier). Strangely enough, FoV is one of the easier ones - actual resolving power gets a lot more tricky because it's effectively relative between two cameras, and MP ratings come into it (most people often ignore this) (eg 1 1Ds3 will out-resolve a 1D3, even though the 1D3 has the 1.3 "effective focal length multiplier").

[rob marshall]

...I'm not helping to make it clear and simple am I?

No you are not, and you ought to be ashamed of yourself!

Here's a simple way to grasp it (and I realize I'm moving into dangerous territory here)

You are sitting in the bathroom... and being bored you pick up a 'lens' which is an empty tube from the toilet roll. On the back of the bathroom door are two pictures of a house with a small amount of surrounding landscape. One is 22x15cm (small sensor), the other is 35x24cm (full-frame). When you look through the tube at the small image (sensor) all you can see is the house as the image is 'cropped' but the rest of the image is still there. When you moved the tube down and look at the larger shot you can see the house and the surrounding area. Nothing is cropped. A lens always 'sees' the same area, it just depends on the sensor size.

[Black Pearl]

You have a very weird bathroom and thats before we get into the you sitting in it bit.....

[MrB]

Are these simplified diagrams any help?



The first diagram shows that a 24mm focal length lens produces the same photo on a small sensor dslr as a 36mm focal length lens produces on a full-frame sensor dslr (factor = x1.5) - the black arrow image on the blue sensor and the red arrow image on the green sensor are in the same proportion as the sensor sizes.



This second diagram shows that the 24mm lens produces an image (the inverted black arrow on the right) that is a much smaller proportion of the full frame sensor (green) than of the smaller sensor (blue), and that the field of view with the full-frame sensor is much larger - a 24mm lens on a full-frame camera is much more of a wide-angle lens than it is on a smaller sensor camera.

Philip

[rob marshall]

You have a very weird bathroom and thats before we get into the you sitting in it bit.....

Well... it's a better explanation than those weird diagrams on post #15 (sorry Philip) I was never any good at maths and physics in schools. So, to the rest of you - when you get confused by all that crop factor c*** just think of toilet rolls

[psubrahmanyam]

Thanks Collin

Now I got it.

EF-S lenses and EF lenses have same field of view,when they are used in crop-factor camera. I thought EF-S lenses are manufactured by Canon exclusively for Cropped bodies , to get ride of short filed of view.

Lat month I bought EF-S 17-55mm 2.8 for my Canon XS after comparing and reading so many reviews with EF 17-40mm 2L. Initially I was thinking of buying 17-40mm 4L to replace my 18-55 kit lens , but got confused with so much technical reading and ended up buying 17-55mm 2.8.

Thanks folks for helping me to understand the concepts on Field of view

[MrB]

... it's a better explanation than those weird diagrams on post #15 (sorry Philip)

Not the kindest of comments, Rob - thank you for the instant apology! Actually, those "weird" diagrams cost me my dinner. I got so absorbed in trying to draw them (using Paintshop Pro) that I forgot about the food in the oven. Not only were its highlights burnt out, it was totally over-exposed beyond recovery!


Philip

[rob marshall]

Not the kindest of comments, Rob - thank you for the instant apology! Actually, those "weird" diagrams cost me my dinner. I got so absorbed in trying to draw them (using Paintshop Pro) that I forgot about the food in the oven. Not only were its highlights burnt out, it was totally over-exposed beyond recovery!


Philip

Philip

You have been around here long enough - 15 posts already! (insert I'm half Jewish smilie) to know that I never mean anything I say and say everything I mean I take it you don't like the toilet roll business then?

What part of Hertfordshire are you from? I was bought up in Hemel Hempstead and also lived in St Albans.

[MrB]

Philip ... I take it you don't like the toilet roll business then?

It should be obvious from my posts that I love the funny (both ha-ha and unusual) use of words, images, situations, etc. Your innovative use of e.g. an Andrex 110mm 0-element standard lens in the bathroom studio was a great idea, but it didn't work for me - the analogy seems to me to be the wrong way round. So, for this problem, apologies for resorting to the boring but useful physics to find an explanation.

As for your second enquiry, best not to put too much info on the www, but you are quite warm!

Philip