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Thread: Should digital compacts give sharper images than DSLRs or film cameras?

  1. #1

    Default Should digital compacts give sharper images than DSLRs or film cameras?

    Hi.....I was reading this section from dpreview on focal length multiplier and I have some doubts which I hope some expert can clarify.

    Footnote on Digital Compact Cameras
    Digital compact cameras are fitted with lenses with short focal lengths to create 35mm equivalent field of views on their small sensor surfaces. Typically the sensor diagonal is 4 times smaller than the diameter of 35mm film. A 7mm lens fitted on such a camera will have the same field of view of a 7mm x 4 or 28mm lens on a 35mm film camera. Just like the digital lenses for digital SLRs, these lenses are designed to generate image circles to cover the smaller sensor. This allows these lenses to be much smaller and cheaper to manufacture. Because of the very small focal lengths used, the depth of field is much larger (2) than digital SLRs or 35mm film cameras with the same field of view.
    Based on the last sentence, does that mean a digital compact will give sharper images on objects in front and behind it compared to DSLR or film as its DOF is larger?

    http://www.dpreview.com/learn/?/key=...gth_multiplier


    Oh and dont mind one more question....those focal lengths listed on digital compacts and lens for DSLRs.......are these the 35 mm equivalent? If no am I right to say that I must
    1. multiply by 1.5 for DSLR lens focal lengths to film
    2. multiply by 4 for digital compact focal lengths to film?
    Last edited by boroangel; 16th December 2005 at 09:56 PM.

  2. #2

    Default Re: Should digital compacts give sharper images than DSLRs or film cameras?

    Sharpness has nothing to do with depth of field. Since the DOF is larger, it just means that everything would be in focus thus its very hard to achieve a narrow depth of field in digital compacts.

    1. The focal lengths stated on SLR lenses are all in 35mm. You have to multiply it by 1.3, 1.5 or 1.6 depending on which camera you use.

    2. For digital compacts I don't think the FLM is the same for all cameras.

  3. #3
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    Default Re: Should digital compacts give sharper images than DSLRs or film cameras?

    What the last sentence seems to say is that the DOF in the images from compact digicams will be larger when compared to the equivalent focal length on a DSLR.

    However, sharpness itself depends very much on the quality of the lens, and also the settings in the camera. High contrast and high sharpening in compact digicams will give the impression that their images are sharper than those straight out of DSLRs, which are comparatively 'neutral'.

    In order to get the 35mm equivalent focal length on a DSLR, multiply the base focal length as stated on the lens by the crop factor. This can be 1.3 (eg. 1DMkIIn), 1.5 (eg. Nikon D70), 1.6 (eg. Canon 350D), 2.0 (eg. Olympus E-500). For the Olympus cameras, you'll need to ask experts in that forum for confirmation on this...I doubt if they call it the 'crop factor' over there.

    The crop factor of each compact digicam is different. To obtain an estimate of this, find out what the 35mm equivalent focal length of your digicam is (eg. 35-105mm) and then divide that by the base focal length which is usually printed on the tip of the lens, together with maximum aperture values.

    In the case of say, a PowerShot A40, the 'crop factor' is somewhere around 6.1!

  4. #4

    Default Re: Should digital compacts give sharper images than DSLRs or film cameras?

    Quote Originally Posted by n0d3
    Sharpness has nothing to do with depth of field. Since the DOF is larger, it just means that everything would be in focus thus its very hard to achieve a narrow depth of field in digital compacts.

    1. The focal lengths stated on SLR lenses are all in 35mm. You have to multiply it by 1.3, 1.5 or 1.6 depending on which camera you use.

    2. For digital compacts I don't think the FLM is the same for all cameras.
    Oh I mean like lets say everything will be in focus (objects in front and behind the subject)....so it wont be blurred and looks more sharp? Or do I have a wrong intepretation of sharpness.

    More sharp = less blurred?

  5. #5

    Default Re: Should digital compacts give sharper images than DSLRs or film cameras?

    Quote Originally Posted by boroangel
    Oh I mean like lets say everything will be in focus (objects in front and behind the subject)....so it wont be blurred and looks more sharp? Or do I have a wrong intepretation of sharpness.

    More sharp = less blurred?
    A picture can be in focus and still not be very sharp.

    If you take the same picture from two similar lenses, set at the same f-stop. They may both be in focus, but they may not have the same sharpness for the objects in focus.

    This is why in post processing software (eg photoshop), you have a Sharpening feature.

    This is why DSLRs also have built in post processing where you can set the sharpness of the photo.

    This is also why camera lenses are often compared for sharpness. Some are sharp right in the middle of the lens and not so sharp at the sides of the lens and so on.

    Sharpness and focus are two separate things.

    Hope this helps.

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