Crop sensor and focal range - is it misleading?

Discussion in 'Photographic Discussions' started by Overread, Sep 22, 2008.

  1. Overread

    Overread has a hat around here somewhere Staff Member Supporting Member

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    Well I was sitting here and trying to get my head round the difference between crop and full frame sensors (again possibly) and hit upon what I think is the cause of much of the confusion.
    People always say that with a crop sensor you get an artificial increase in focal length - due to the area of lost lens area because of the smaller sensor.
    Yet when one looks at this statement it is misleading since it gives the impression that the lens is getting an increased "range" of zoom by being used on a crop sensor when - in fact - it is mearly being cropped in camera at its correct focal length (zoom range).

    Now since zoom range is how people perceive focal length when they are told that a crop gives them more zoom they assume then that fullframe will result in the lens getting reduced zoom range -ergo they won't get as close to the subject with the camera as with their crop sensor.

    Is this description born of the attempt by people to view a posetive side of using crop sensor - as opposed to saying that the sensor is cropping the shot smaller?
    Or am I barking up the wrong tree?
     
  2. Alex_B

    Alex_B No longer a newbie, moving up!

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    First of all, the effect of different media sizes on the images from lenses of the same focal length has been there fore ages. There have always been many formats (MF, LF, ...)

    Well, some people say (beginners and some salespersons) that, but the statement is plain wrong. All which changes is the angle of view. And then you should talk about what focal length you would need on the larger format, to get the same angle of view as on the smaller format.

    A lens with a 5x zoom is always a 5x zoom, on whichever sized sensor you use it. What is a 20-40mm lens on full frame, will on a 1.6 crop sensor be with respect to the angle of view like the equivalent of a 32-64mm. But in both cases it is a 2x zoom. Only on the smaller sensor it is shifted away from the wide angle towards the tele end.

    People often confuse zoom and tele. They say zoom but mean telephoto.

    It is simply born of ignorance, and of many people who know nothing about cameras wanting to buy cameras. Salespeople adapt to that ;)

    People want simple explanations, even if they are wrong.

    And with my 300mm prime, a 1.6 crop sensor does help me getting more tele effect and hence larger animals in my shot! So this is an advantage if image quality is comparable.
     
  3. Overread

    Overread has a hat around here somewhere Staff Member Supporting Member

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    ahh thanks Alex!
    it seems that salespeople are causing a lot of confusion - methinks should really get and read one of those more technical photography books!
     
  4. Alex_B

    Alex_B No longer a newbie, moving up!

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    well, the salespeople only adapt to the market, in fact they have to. and if the market holds a lot of people who do no know much, it is not their job to educate them thoroughly. They need a quick and dirty solution.

    Depending on the shop, of course there are also a lot of salespeople, who know nothing about photography. In particular at the big discounters.
     
  5. Bifurcator

    Bifurcator TPF Noob!

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    Yeah I wish angle of view or something different was always used instead of mm. The mm specification doesn't even match from lens to lens or maker to maker. My 28mm (35mm equiv) is 1.36 times the angle of view as the Canon Kiss (they're called Kisses instead of Rebels in Japan) kit lens also set to 28mm. It's just not a good unit of measure for determining scene coverage. The problem here of course is that my camera is displaying mm in 35mm equiv view angles and the canon lens isn't.

    If you always have to stop and consider crap factor [Freudian slip I meant "crop factor"] everytime you look at the focal length it makes the numbers pretty meaningless unless you can memorize all the different crop factors of every different camera. :(
     
    Last edited: Sep 22, 2008
  6. Village Idiot

    Village Idiot No longer a newbie, moving up!

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    Crop sensors give you a different field of view and not a different focal length.
     

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