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Thread: Lenses in Digicams vs SLR Lenses

  1. #1
    vince123123
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    Default Lenses in Digicams vs SLR Lenses

    I noticed that the lenses on point n shoot / prosumer digi cams seem to be really good in zoom range and aperture. a good case in point is the panasonic lumix fz-10 - 35 - 400 equiv with f2.8 constant....

    then it brings me to SLR lenes...the widest range we have rite now is at best 3x, either the ubiquitous 70-200 f2.8s or the 100-300 f2.8, and those are monster glass lenses.

    the qn is, are the specs on the digicam lenses accurately and equivalent? how do they do it with less glass and greater zoom range + aperture?

    thanks!

  2. #2
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    One of the main differences actually lies in the sensor (CCD/CMOS) size. DCs have a much smaller sensor, hence their lenses are proportionally smaller too. The resolving power of such smaller lenses are actually lesser than those of the bigger lenses used on SLRs. What manufacturers are trying to do is to cramp more pixels into those smaller sensors so that they have a higher megapixel count and thus more resolution. However, this does not change the fact that the lens does not resolve the image as well. Furthermore, a higher pixel count on a smaller sensor also causes a higher noise ratio.

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    aperture is actually a measurement based on dimensions (it's a ratio I think). it's actually not indicative of image quality.

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    Quote Originally Posted by vince123123
    .....

    then it brings me to SLR lenes...the widest range we have rite now is at best 3x, either the ubiquitous 70-200 f2.8s or the 100-300 f2.8, and those are monster glass lenses.

    ......
    erm, I actually feel that it's not a good thing to have a very big zoom range. Granted that you have more convenience and whatnot, it's not going to be good for image quality. Check out how many 10X zooms Nikon and Canon have made before, and their respective user ratings. Now compare that to the number of dinky digicams boasting about 10X, 12X zooms. If these zooms are really good, both Nikon and Canon would be manufacturing them by the hundreds liao.

    moral of the story: you get what you pay for.

  5. #5
    vince123123
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    just to clarify

    so that means that the main reason is the smaller sensor size, and which also means that the lenses are poorer in resolving power than SLR lenses, and coupled with the smaller sensor sizes, overall give poor quality images rite?

    also it also means that when comparing slr and digicams, megapixel counts do not quite correlate?

    however in terms of amount of light entering, the F2.8 on a digicam is the same as the F2.8 SLR cousins?

    finally the panasonic one seems to be using a leica lens, wonder whether the 12x on it would make it only average though. nevertheless, such a big zoom range at F2.8 constant kinda surpirsed me for a second.

  6. #6

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    I'm impressed by Panasonic's FZ10's specs.

    The only disadvantage you may get with super zoom lens are pincushion and barrel distortion. The longer the range the more profound cushioning and distortion error occurs- reminds me of you can't have the best of both worlds...

    The aperature is also impressive. Running a full f/2.8 throughout only means brighter and more vibrant colours, faster shutter speeds and a little sometimes appreciative shallow DOF SLR effects that otherwise would be very expensive to deliver. But been said, the CCD on such cameras are usually much smaller compared to a DSLR, and hence if you're thinking of having an extreme shallow DOF, it may not be possible- but usually no one in the right frame of mind would frequently wanna shoot that way.

    The only assurance on the buyer would be to read up technical reviews done by unbiased 3rd parties on the performance of the camera in terms of resultant imaging quality.

    Yes, it's true, depending on your needs, alot of such cameras make economic sense without compromising too much. And not many people can tell if you had shot it with a DSLR or a P&S nowadays.

  7. #7

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    Quote Originally Posted by vince123123
    just to clarify

    so that means that the main reason is the smaller sensor size, and which also means that the lenses are poorer in resolving power than SLR lenses, and coupled with the smaller sensor sizes, overall give poor quality images rite?

    also it also means that when comparing slr and digicams, megapixel counts do not quite correlate?

    however in terms of amount of light entering, the F2.8 on a digicam is the same as the F2.8 SLR cousins?

    finally the panasonic one seems to be using a leica lens, wonder whether the 12x on it would make it only average though. nevertheless, such a big zoom range at F2.8 constant kinda surpirsed me for a second.
    as was mentioned earlier, the aperture number is a ratio, rather than an absolute number. Thus f2.8 for a DSLR and a Compact DC like FZ10 would refer to a different size.

    Frankly, I feel that having a zoom range is a really a matter of convenience, a really big matter of convenience at that. Also, with a 12X zoom camera, i can shoot more things without having to risk life and limb to climb and scramble to get that perfect angle and composition.

    I wouldn't say that Nikon and Canon feel that a powerful zoom is useless (because Canon just came out with a 10X zoom camera with IS), I personally feel that they r targeting a different market. While the FZ1/10 is hardly a professional camera, it's real value for money and not altogether a 'lousy' camera that I would throw the phrase 'you get what you pay for' at.

    adding to this, yes, pictures taken with my FZ1 is rather noisy, can't really be printed or displayed without some 'noise-washing'. While i would really love to own a DSLR (even a discontinued 2mp version), i don't have the spare cash to buy a kit with a range resembling a 12X zoom camera.

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    To calculate the real aperture size do the following:

    Based on CP5700.

    35mm-280mm equivalent = 8.9mm-71.2mm

    35 / 8.9 ~= 3.9

    f/2.8 x 3.9 = f/11.

    The f/2.8 is not entirely the same as on a SLR thus the price difference, not forgetting the size of the elements used in a DC and lens is different, thus the cost.

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    espn, what you calculated is the "aperture" equivalent for depth of field effect. but the aperture of f/2.8 is still f/2.8 (just like the actual focal length is 8.9mm but in 35mm equivalent terms = 35mm).

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    Quote Originally Posted by vince123123
    just to clarify

    so that means that the main reason is the smaller sensor size, and which also means that the lenses are poorer in resolving power than SLR lenses, and coupled with the smaller sensor sizes, overall give poor quality images rite?

    also it also means that when comparing slr and digicams, megapixel counts do not quite correlate?

    however in terms of amount of light entering, the F2.8 on a digicam is the same as the F2.8 SLR cousins?

    finally the panasonic one seems to be using a leica lens, wonder whether the 12x on it would make it only average though. nevertheless, such a big zoom range at F2.8 constant kinda surpirsed me for a second.
    For the light part : The amount of light u capture is of course different, however, if u are talking abt the light/area (which is essentially ~ exposure), its the same. Like wat espn had said, the f2.8 isn't exactly the same. Proportionally to sensor size, it is. But in actual, u aren't able to have the same shallow DOF like SLRs with a f2.8

  11. #11

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    not exactly sure..but here's my take

    aperture (f stop) = focal length / physical size of aperture. ( i think everyone agrees with this)

    regardless of size of cam, 35mm, medium format, canon ixus etc. the above rule applies.

    exposure (ev): no matter what camera u use, the same settings (eg: ISO100, F1.0, 1s, will give the same exposure value.http://www.chem.helsinki.fi/%7Etoomas/photo/ev.html
    small sensor, small physical aperture allow less light, but exposure is the same. (because smaller cam has smaller focal length, refer to above equation)


    DOF: depends on physical size of the aperture, and subject to background distance. the bigger the physical size of aperture, the more shallow the DOF, draw a light ray diagram to prove to yourself. Hence small digicams, canot achieve bokeh except in macro mode, when subject distance is much smaller than background distance.

    it is indeed stunning to learn that 10X zoom with F2.8 is possible.

    I stand to be corrected
    cheers

  12. #12
    vince123123
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    so conclusion =

    f2.8 is same exposure, DOF different.

    yeap that seems to be what i was asking about tks all for the confirmation

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