Myths About Cropped Sensors (Two Photographs)

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The myths about cropped sensors are almost as subtle as this squirrel’s expressions. The way those selling cameras describe it you would think that a 100mm lens on 1.5 cropped sensor DSLR would be equivalent to 150mm lens on a full frame camera in every aspect. However only the angle of view changes not the magnification. The magnification remains that of a 100mm lens. The angle of view is the width of the view you get, telephoto lenses have narrow views and wide-angle lens, just as the name says ,have wider angles of view. There is an illusion of magnification but the lens is still 100mm and that illusion would disappear if you saw the same photo taken with a true 150mm lens at an equivalent aperture (which also changes with the size of the sensor). You hear that cropped sensors have deeper depth of field at any given aperture. In fact you need to multiply the aperture by the crop factor, a F2.8 lens is actually F4.2, it may also be a factor in letting in less light than on full frame camera with a larger sensor. A good selling point for full frame sensors may be that they are better performers in low light. I shoot only cropped sensors so the issue here is not that cropped sensors are bad, but that some of the advertising is a little too subtle.




9 responses

  1. An interesting post and although I agree with most of it I don’t think you’re right in one respect. An F2.8 aperture lets in F2.8 of light regardless of the sensor size. As you say the aperture needs multiplying by the crop factor in terms of DoF, but not in terms of light/speed. I use crop sensors too (m43).


    February 12, 2017 at 3:36 am

    • What I have read is that the size limits the amount of light that can be captured, just like a solar panel collects more the larger it gets.


      February 12, 2017 at 6:11 am

    • A friend has pointed out that sensor size is only one factor in brightness, others include optic path and megapixels, no one of them a determinant. Zoom And prime lenses would make a difference too. My blanket statement is shorthand.


      February 12, 2017 at 7:57 am

    • I made a slight change to the post to reflect our exchange.

      Liked by 1 person

      February 12, 2017 at 8:36 am

  2. F U L L S P E C T R A

    Beautifully explained and gorgeous shots, Victor! 😀


    February 12, 2017 at 6:09 am

  3. Hi Victor, I’m not sure I explained myself very well either. My point is probably best explained by an example. Let’s say that I take an image with a full frame camera with these settings 100mm; F5.6; 1/200th;ISO100. To get the equivalent focal length and DoF using an m43 camera with a crop factor of x2, I would need to shoot at 200mm and F2.8. However to get the same exposure I’d still be shooting at 1/200th and ISO100 – in other words you don’t have to apply the crop factor to the shutter speed or ISO, because applying it to the aperture is enough.


    February 12, 2017 at 9:27 am

    • Agreed, but my point, with the correction from my scientist friend, is that there are other factors that make cameras more or less light sensitive, like the amount of glass in the lens, whether its a single stop throughout range My apologies for cutting a corner. I appreciate your bringing it to may attention.

      Liked by 1 person

      February 12, 2017 at 9:33 am

  4. Sorry I meant I would need to shoot at 50mm not 200mm.


    February 12, 2017 at 9:29 am

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