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Thread: Crop factor

  1. #21

    Default Re: Crop factor

    Quote Originally Posted by gymak90 View Post
    This thread has lots of posts that make the idea of crop factor, much more confusing than what it really is.

    Anyway, the green box refers to the APS-H sensor which gives 1.3x crop factor. APS-H sensor only by some Canon 1d series dslrs.

    So crop factor, is just about the sensor being smaller than full frame(which is 36X24mm). As a result, the field of view or viewing angle, is less than what it is on full frame.

    Don't believe? Go try it with your own eyes. Put your 2 palms next to your eyes. And obviously you can no longer see the stuffs at the sides.

    What people like to say is sometimes misleading. Mounting a 100mm lens on 1.6x crop factor sensor DOES NOT turn the lens into 160mm focal length. No such magic. No such trick. No such good deal.

    What happens is people often leave out is the phrase: field of view.
    Look my friends, a 100mm lens on 1.6x crop factor sensor, gives you the equivalent field of view as that of 160mm on full frame. Which is to say, your view becomes narrower. That's all. Therefore, the objects in your picture, do not magnify. They do not become bigger. They remain as normal sized.

    Using my 'palm-next-to-eye' example, you won't see things become bigger right? Do you? If yes, something's wrong



    I think the above answers your question. No you don't see more details, because your subject won't become bigger in anyway. Also it depends on the number of pixels and pixel density. Number of pixels is associated with resolving power of the sensor.
    By field of view you mean when looking through the eyepiece?

  2. #22

    Default Re: Crop factor

    Oops. Better edit this away, was contradicting to a gymak90's post.
    Last edited by PyeeL; 24th November 2008 at 11:34 PM.

  3. #23
    Member gymak90's Avatar
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    Default Re: Crop factor

    Quote Originally Posted by gameboyz View Post
    By field of view you mean when looking through the eyepiece?
    Well theoretically correct. Because in slrs, what the lens sees is you what you will see through the viewfinder.

    However, most slrs, have a viewfinder coverage that is less than 100%. Mostly at 95% coverage. Which means, you'll be seeing slightly less than what the lens is seeing.

    Regarding your earlier post, I'm not very sure what you're saying, so I can't say you're right.

    But just know that whenever you use a lens of longer focal lengths, say comparing 100mm and 160mm lenses, the field of view you get from 160mm is always narrower than the 100mm lens. Of course by using a true 160mm lens, you will also get greater magnification than the 100mm lens.

    In cropped sensors, similarly, you will get the narrow view of the 160mm lens, when you mount a 100mm lens on 1.6x crop sensor. The difference here is, you don't get the magnification.
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  4. #24

    Default Re: Crop factor

    Quote Originally Posted by gameboyz View Post

    So basically, crop means you get a smaller picture, but quality won't be affected. The "160mm" lens has the view of a 160mm telephoto lens, but when you take the picture it results in the magnification of a 100mm telephoto lens and NOT the 160mm.
    It's more like... The lens STILL captures the whole frame, but the sensor then "cuts out" (or, to use the correct term, crops) the center portion out. So by using a crop sensor, you're discarding the whole outer portion of the image, which makes it *look* like you mounted a 150mm (on a 1.5x crop) on a full frame body. It has a similar field of view.
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  5. #25
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    Default Re: Crop factor

    to put it simply
    using a Film camera, take a picture
    then have it printed 4R

    this is Full frame or FX sensor

    then take the 4R picture and cut off the sides
    this is roughly what you get with a crop sensor or DX sensor

  6. #26
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    Default Re: Crop factor

    just imagine your camera to be a FF (Full Frame) body, take a photo, and crop out the red box. that is what you get on a DX body. Magnification is still the same, but field of view is more narrow. that is what is meant by cropped sensor. it does that cropping for you, while still retaining that 10.2MP for you in that cropped image, in layman terms.
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  7. #27
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    Default Re: Crop factor

    Quote Originally Posted by fitzy View Post
    What about Canon EFS lenses, do I need to multiply by 1.6 to get the approx focal lenght?
    Crop factor is based on the ratio between focal length of the lens and the sensor size. No - you don't get the 'new focal length' as result. You will get the equivalent Field of View. Focal length and Field of View are not the same although they appear to be. A lens of 50mm focal length will always have the same focal length, regardless whether mounted on crop sensor body or Full Frame body.
    EFS lenses produce a smaller image circle, enough for the smaller sensor. Due to the physical construction EFS lenses cannot be mounted anymore on Full Frame cameras (e.g. Canon EFS 18-55), whereas third party lenses designed for crop sensor cameras still can be mounted on Full Frame but will cause heavy vignetting since the image circle is too small (e.g. Tamron 17-50). In the viewfinder it will look as if you look through a tube. Interesting effect if desired.

  8. #28
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    Default Re: Crop factor

    Quote Originally Posted by gameboyz View Post
    Because in layman terms focal length means zoom right? Telephoto lens with super zooming has high focal lengths ..
    No. You might want to do a definition search on focal length. Focal length is definitely not zoom.

    Quote Originally Posted by gymak90 View Post
    ...
    But just know that whenever you use a lens of longer focal lengths, say comparing 100mm and 160mm lenses, the field of view you get from 160mm is always narrower than the 100mm lens. Of course by using a true 160mm lens, you will also get greater magnification than the 100mm lens.
    ...
    Actually, someone did a back to back test of the 20D with a 10-22mm lens mounted and set to 10mm (the 20D is a 1.6x crop machine) compared to a 5D with a 16-35mm mounted and set to 16mm. The two frames were stacked, one over another, and the FoV of both frames were identical.

  9. #29

    Default Re: Crop factor

    Okay I understand already thanks.

    So the picture will look like a 150mm lens, but if taken with a true 150mm lens on a fullframe dslr it will have higher res and a bigger picture.

    Cheers.

  10. #30

    Default Re: Crop factor

    gameboyz started a fierce debate here...

    Don't worry about it so much... Just know that a 100mm lens on a D60 (1.5x crop factor) will give you the field of view of a 150mm lens on a full frame or film camera...

  11. #31
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    Default Re: Crop factor

    Sorry to dig up an old thread but i'am intending to get a copy of the sigma 30mm f/1.4, however i have a few doubts about the fov on my camera.

    I'am using the sony alpha100 w/18 - 70mm kit lense, would the fov with the 30mm f/1.4 mounted on my camera have the same fov as when i'am shooting at 30mm using my kit zoom lense?

    Hope to hear some replies soon. Thanks !!

  12. #32
    Senior Member Galdor's Avatar
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    Default Re: Crop factor

    Quote Originally Posted by skareb View Post
    Sorry to dig up an old thread but i'am intending to get a copy of the sigma 30mm f/1.4, however i have a few doubts about the fov on my camera.

    I'am using the sony alpha100 w/18 - 70mm kit lense, would the fov with the 30mm f/1.4 mounted on my camera have the same fov as when i'am shooting at 30mm using my kit zoom lense?

    Hope to hear some replies soon. Thanks !!
    Yes, it would be the same.
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  13. #33
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    Default Re: Crop factor

    Awesome! Thanks dude

  14. #34
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    Default Re: Crop factor

    OT a little....

    Wah! Crop factor 1.6x already like that..
    Olympus 2x crop factor, isn't it more close-up.

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