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Thread: DOF on prosumer camera and DSLR

  1. #1

    Default DOF on prosumer camera and DSLR

    Hi guys,

    Just curious on one question:

    Do I get the same DOF on a DSLR and 'prosumer' digital camera if both cameras are using exactly the same setting, including focal length and focussing distance???? Do I get better DOF on a DSLR?

    Just want to know since a prosumer camera with a F2.8 lens is WAY cheaper than a DSLR with F2.8.....
    Sony a7rii + Batis 2/25
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  2. #2
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    Quote Originally Posted by Hein
    Hi guys,

    Just curious on one question:

    Do I get the same DOF on a DSLR and 'prosumer' digital camera if both cameras are using exactly the same setting, including focal length and focussing distance???? Do I get better DOF on a DSLR?

    Just want to know since a prosumer camera with a F2.8 lens is WAY cheaper than a DSLR with F2.8.....
    just one point... eg the F value goes up when you zoom in..

    ie.. u can never get F2.8 on a 50mm equil on a 35mm camera...

    am i right?

  3. #3

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    Quote Originally Posted by Michael Ang
    just one point... eg the F value goes up when you zoom in..

    ie.. u can never get F2.8 on a 50mm equil on a 35mm camera...

    am i right?
    There are 50mm F1.4 primes available as well as F1.8..

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    Quote Originally Posted by junyang
    There are 50mm F1.4 primes available as well as F1.8..
    hi,

    maybe i should rephrase my query....

    i mean to say, i cannot get a F2.8 on my 707 based on 50mm focal length, right? i noticed that once i zoom in, the F number seems to go up and cannot be brought back down...

    thus could never get the same DOF as a 50mm prime lens...

  5. #5

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    If im not wrong. F2.8 on a digital camera is probably equal to F8.0 on an SLR/DSLR due to certain limitations..

  6. #6

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    I think it's quite impossible to get the same focal length on your prosumer vs. your DSLR. For e.g., the G3 focal length is 7.2mm - 28.8mm, which works out to be 35mm - 135mm on the 35mm equivalent. The f-multiplier would be 35/7.2 = 4.86. Thus, f/2.0 on the G3 at 7.2mm would be equivalent to f/9.72 on the DSLR at 35mm.

    The DOF difference is due to the physical differences in apperture sizes.

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    f-stop is calculated by diving the focal length of the lens by the diameter of the aperture.

    hence, for a 35mm f/2 lens, the size of the aperture is
    35mm / 2 => 17.5mm

    for a 35mm f/1.4 lens, the size of the aperture is
    35mm / 1.4 => 25mm

    but for an equivalent compact digicam, it would be more like,
    7.2 / 2 => 3.6mm

    and remember, the larger the hole in a pinhole camera, the blurrer it is. similarly this hole is what we call the aperture. hence by the physical size alone, we can see that the aperture difference is massive, which is the reason that causes bokeh...

  8. #8

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    Quote Originally Posted by darkness
    I think it's quite impossible to get the same focal length on your prosumer vs. your DSLR. For e.g., the G3 focal length is 7.2mm - 28.8mm, which works out to be 35mm - 135mm on the 35mm equivalent. The f-multiplier would be 35/7.2 = 4.86. Thus, f/2.0 on the G3 at 7.2mm would be equivalent to f/9.72 on the DSLR at 35mm.

    The DOF difference is due to the physical differences in apperture sizes.

    You are saying the DOF I get on a prosumer camera @ 7.2mm F2.8 will be similar to a 35mm @ 35mm F13.6.. Meaning it's same DOF as a DSLR @ 21.8mm F8.4

    Based on this argument, I can have nicer portrait pictures with a 16-55 F3.5-5.6 lens compared to my 7.8-46.8 F2.8-3.1 lens on my prosumer(Fuji S602Z).... Any comments on this??
    Sony a7rii + Batis 2/25
    Gitzo 1530 + Markins Q3

  9. #9

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    Quote Originally Posted by Hein
    You are saying the DOF I get on a prosumer camera @ 7.2mm F2.8 will be similar to a 35mm @ 35mm F13.6.. Meaning it's same DOF as a DSLR @ 21.8mm F8.4

    Based on this argument, I can have nicer portrait pictures with a 16-55 F3.5-5.6 lens compared to my 7.8-46.8 F2.8-3.1 lens on my prosumer(Fuji S602Z).... Any comments on this??
    Short answer. Yes.

  10. #10

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    Quote Originally Posted by Hein
    Based on this argument, I can have nicer portrait pictures with a 16-55 F3.5-5.6 lens compared to my 7.8-46.8 F2.8-3.1 lens on my prosumer(Fuji S602Z).... Any comments on this??
    Except that your subjects will have big noses...

  11. #11

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    Quote Originally Posted by darkness
    Except that your subjects will have big noses...
    Bigger nose??? Maybe not... the 7.8mm should be comparable to 21mm on a DSLR.. Am I wrong??
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    Quote Originally Posted by Hein
    Bigger nose??? Maybe not... the 7.8mm should be comparable to 21mm on a DSLR.. Am I wrong??
    right and wrong. the picture should look exactly the same, but the DSLR suffers from the 1.3x, 1.5x or 1.6x crop factor, so the viewing angle may be different... use the term, SLR instead.

  13. #13

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    Quote Originally Posted by sehsuan
    right and wrong. the picture should look exactly the same, but the DSLR suffers from the 1.3x, 1.5x or 1.6x crop factor, so the viewing angle may be different... use the term, SLR instead.
    I was thinking that my 7.8mm is equivalent to 35mm on a 35mm camera, which will be equivalent to 21mm after cropping by 1.6x.. Is that true?
    Sony a7rii + Batis 2/25
    Gitzo 1530 + Markins Q3

  14. #14

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    Quote Originally Posted by Hein
    I was thinking that my 7.8mm is equivalent to 35mm on a 35mm camera, which will be equivalent to 21mm after cropping by 1.6x.. Is that true?
    1.6x is a focal length multiplier (FLM), therefore you take whatever lens you attach and multiple by 1.6. For e.g., a 28mm lens becomes 44.8mm on a DSLR with 1.6x FLM.

    If assuming that you have a lens that is 21.875mm, which is 35mm after FLM, then you will achieve the same picture as using 7.8mm (which is 35mm equivalent) on your digicam. However, the bokeh will not be the same due to the physical size difference of the apperture (but the f number can be the same!!).

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    Quote Originally Posted by darkness
    1.6x is a focal length multiplier (FLM), therefore you take whatever lens you attach and multiple by 1.6. For e.g., a 28mm lens becomes 44.8mm on a DSLR with 1.6x FLM.

    If assuming that you have a lens that is 21.875mm, which is 35mm after FLM, then you will achieve the same picture as using 7.8mm (which is 35mm equivalent) on your digicam. However, the bokeh will not be the same due to the physical size difference of the apperture (but the f number can be the same!!).
    slightly wrong phrasing in your reply, darkness. a 28mm lens still remains 28mm on a DSLR, but the angle of view is that of a 44.8mm lens (virtually) because most of the image circle formed is not used because of the smaller sensor size.

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