Resolution with APS sensor vs. full-frame

Discussion in 'Digital Photography' started by Paul Flackett, Sep 25, 2005.

  1. I'm having difficulty getting my head around the variables with DSLR's.
    Would I be correct in thinking that an 8MP APS sensor camera like the
    EOS 20D would be just as good for the bird photographer as the 5D
    (costing considerably more) with the same lens when the image from the
    latter is cropped to the same area as that captured by the former? Or is
    it not quite as simple as that - is the resolution better by default
    with a full-frame sensor?

    I've always considered the 1.5 factor to be a real advantage with my 20D
    allowing me to get more magnification for my money. What would I be
    gaining by upgrading to the 5D?
    Paul Flackett, Sep 25, 2005
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  2. 5D, 20D comparison:

    They way I see it: 20D is 5 frames/sec, 5D is 3.
    5D has 8.2 microns pixels versus the 20D 6.2 micron
    pixels. The larger pixels will make for better images
    in general and sharper images/pixel for a given lens.

    The smaller pixels of the 20D will give more pixels per given
    cropped area. With processing, I would bet there would be
    a slight advantage to the 20D images compared to the
    same area cropped 5D, but not as much as the number
    of pixels would indicate. For birds, the higher frame
    rate could be an advantage with the 20D.

    Then the question 5D versus 1Ds Mark II (is the price
    increase of the 1dsII worth it over the 5D)? Will the 5D
    put pressure to drop the price of the 1DsII?

    Roger N. Clark (change username to rnclark), Sep 26, 2005
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  3. For the bird photographer, the 64-dollar question is how well does the
    (slightly) improved AF tracking (with the 6 extra sensors) work with a 1.4x
    TC as opposed to the 20D's AF without the TC.
    (1) 25% better linear resolution (using lenses with the same FOV)
    (2) Lower noise (should be noticeable at ISO 800 and above)
    (3) Better dynamic range (should be noticeable at ISO 100)
    (4) Spot meter
    (5) Interchangeable focusing screens
    (6) Ability to get a 12mm FOV with the Sigma 12-24.
    (7) Fisheye
    (8) The 24mm TSE acts like a 24mm TSE instead of a 38mm TSE

    Note that all of these are enormous for landscape photographers, not bird

    David J. Littleboy
    Tokyo, Japan
    David J. Littleboy, Sep 26, 2005
  4. Paul Flackett

    Bill Guest

    It's not as simple as that.

    There are advantages to both imaging sensors, and it depends a lot on
    what you want to accomplish. But comparing the 20D and 5D imaging
    sensors, you will find the 5D has a larger "receiving area", which
    should translate into less noise and a brighter image with the same
    lense and same conditions.
    This is a common misconception - it's a crop factor, not any kind of

    Putting a 200mm lense on a 20D does _NOT_ get you any closer to the
    subject than using the same 200mm lense on a full frame camera.

    A 200mm lense is a 200mm lense, on a full frame and a 1.6x body. The
    difference is _ONLY_ the field of view, or how wide the final image will
    appear and how much scenery will be visible around the subject.

    To see an example image of what this means, scroll about a quarter of
    the way down the following page:

    Further down, another example shows the difference between full frame
    and 1.6x crop with a 400mm lense and how the zoomed size appears larger.
    Lots of things related to features and performance, and slightly better
    image quality.

    I think the biggest advantage would be the full frame sensor that allows
    you to use a 28mm lense as it was intended. For wildlife photography,
    it's not a major factor.
    Bill, Sep 26, 2005
  5. Paul Flackett

    Stacey Guest

    Bill wrote:

    Actually it changes the FOV which is what also happens when you use a higher
    magnification lens. Why people are so hung up on relating everything to
    35mm full frame mm of focal length is something I'll never understand. Or
    why this "It's works like that mm of lens is suposed to". Focal length and
    FOV changes with format whether it's 6X9, 4X5, 4/3 or APS.

    FOV is all that really matters. A 90mm lens is a nice wide lens on a 4X5,
    should I be upset and demand that any camera should have a wide FOV with a
    90mm lens? Of course not, that would be a silly arguement.
    In real use it does. A 200mm lens is a wide angle lens on an 8X10 camera,
    doesn't mean it's still a wide angle lens used on a 20D.

    Using the same 200mm lens on a 20D will get you closer than that same lens
    used on a 35mm camera or a 5D, unless you crop the image of course. Then
    you have less MP so it's doubtful the image quality would be as good. And
    why pay $3500 to "upgrade" if your going to end up cropping to a smaller MP
    final image?
    Which is all that matters, the mm of the lens is a meaningless number. FOV
    is all anyone should care about, period! Why people rant about this "A
    200mm lens is a 200mm lens" is absurd. From what you're saying, there is no
    difference between


    except the first has an angle of view of 55 deg and the second of 12 degree
    like that's of no real concern to the end user and we should be FOCUSED on
    the number of mm the focal length of the lens is..

    Not unless he buys new longer/larger/heavier/more expencive lenses so he has
    the same FOV across the whole sensor.
    Stacey, Sep 26, 2005
  6. Most people will only need one new lens, the longest one. All the others
    will work fine. Unless they bet on the wrong horse.

    David J. Littleboy
    Tokyo, Japan
    David J. Littleboy, Sep 26, 2005
  7. Paul Flackett

    ASAAR Guest

    I think it would be more than a slight advantage, unless I'm
    making a calculation error somewhere. If the 20D's sensor was as
    large as the 5D's sensor it would have 6.2 x 1.6 x 1.6, or about
    15.9mp. So if the same focal length is used with both sensors, any
    subject's image that fits within both sensors (as would be the case
    where you can't get close enough to a bird to fill the frame), the
    image on the 5D's sensor would utilize 8.2 / 15.9, or 0.52 times the
    number of pixels. That is, the image in the 20D would contain
    nearly twice the number of pixels. The 5D would have the edge only
    if the bird was close enough so that the 20D would have to use a
    much shorter focal length than the 5D to keep the bird's image from
    exceeding the size of the sensor.
    ASAAR, Sep 26, 2005
  8. Paul Flackett

    Stacey Guest

    Which will also be the most expencive, heaviest, largest lens they've ever

    If they were using a 200mm f2.8 1.68 pound lens and liked this FOV on the

    They'd have to get at least a 300 f4 2.6 pound lens at twice the price and a
    full stop slower.

    If they want the same lens speed, add 4.5 pounds to the weight of the 200mm
    lens and about $3000 more bucks!

    Yea that's nothing for anyone to concern themselves with. Just plop down
    $3500 for the body upgrade and $3800 for a new lens to cover the same FOV
    at the same speed and haul around 5 -more- pounds of camera.
    Stacey, Sep 26, 2005
  9. Paul Flackett

    Stacey Guest

    ASAAR wrote:

    No way, the 5D RULES!!! Don't you know anything? :)
    Stacey, Sep 26, 2005
  10. Not quite - you are using the wrong resolution for the 5D, it has
    12.9Mp, not 8.2Mp.

    Cropped to the same focal plane area, the pixel resolution is simply the
    square of the pixel pitch. On the 20D that is 6.4um; on the 5D it is
    8.2um, so the 20D will have around 1.64x as many pixels in any given
    crop size, including the full APS crop of the 20D.

    However, pixel counts isn't everything - all pixels are not equal. Those
    smaller pixels demand more performance out of the optic to be properly
    resolved - same problem that besets P&S digital cameras, albeit on a
    different scale. Even with diffraction limited optic, for anything
    above f/11 the actual resolution of the image is determined by the lens
    not the 6.4um pixels. For 8.2um. that increases by over a stop. So if
    you are shooting at f/16 you won't really be getting 8Mp of information
    on the image with the 20D, more than 50% of it is superfluous redundant
    data. In addition to which, the larger pixels from the 5D *ought* to be
    (since they aren't in general supply yet that is an assumption) more
    sensitive and less noisy.

    Taking everything into account, what actually matters in these type of
    estimates is usually total focal plane area. How it is diced up into
    small noisy pixels or large sensitive ones is generally a second or
    third order effect as long as the pixel sizes being compared are within
    the useful range photographically.
    Kennedy McEwen, Sep 26, 2005
  11. Paul Flackett

    Bill Hilton Guest

    Paul Flackett writes ...
    Most bird photographers would do better with the 20D due to the 1.6x
    crop (actually EVERY pro bird photographer I know who uses Canon gear
    uses a 1D Mark II now instead of full frame bodies). I have a 1x
    camera (1Ds, 11 Mpix) and a 1.3x camera (1D M II, 8 Mpix) and while I
    prefer the image quality of the 1Ds, for birds and wildlife I use the
    MII about 8x as often (I usually have both bodies available) because of
    the faster AF, higher frame rate and longer "reach" ... we can print
    11x14" easily and sometimes 16x20" with these images and that's enough
    for bird images.
    It is, and I wouldn't upgrade for just birds or bears or other wildlife
    shooting where the extra reach is a bonus ...

    Bill Hilton, Sep 26, 2005
  12. Paul Flackett

    winhag Guest

    So what your saying is that the 20D and th 1D MII are for the birds! :)

    It seems to me that the answer is application dependent. As a
    I think someone who has an arsenal of lenses he/she has built up over a
    of years does not want to have them subjected to a crop or FOV 'shift'
    accomodate a smaller than full frame sensor.
    winhag, Sep 26, 2005
  13. Paul Flackett

    Bill Hilton Guest

    Winhag writes ...
    Paul is a very good bird photographer and he asked specifically about a
    camera for birds, so I was just answering his "application dependent"
    question, which admittedly is a departure from internet newsgroup
    tradition :)
    I'm packing for a "generalist" trip right now and the 1Ds is going
    along and the 1D Mark II is getting left at home, though it's more
    because I prefer 11 MPix over 8 Mpix and won't need 8 fps to photograph
    fall foliage than because of the FOV. One really wide lens would fix
    that problem quickly enough.

    Bill Hilton, Sep 26, 2005
  14. Paul Flackett

    eawckyegcy Guest

    For bird photography, probably nothing. For studio, wide-angle
    ("landscape"), or macro work, a fair amount. If you are upgrading from
    a 20D for wildlife stuff, you should consider a 1DMkII at this time:
    the 8fps is _very_ useful.
    eawckyegcy, Sep 26, 2005
  15. That last point is key, yes. I finally invested in a new wide lens to
    extend my digital wide end to match what I had on film (Tokina
    12-24mm). Meanwhile, the much more expensive fast long lenses all get
    a little better :)
    David Dyer-Bennet, Sep 26, 2005
  16. Paul Flackett

    winhag Guest

    But it is not always that simple. For example suppose you like to shoot
    on the street with your fast 50mm f/1.4 lens. With the 1.6X factor,
    that is now an (has the same FOV of a 35 mm full frame) 80mm lens, not
    quite the same beast. I have seen 30mm f/1.4 lenses coming out to
    satisfy that need. But I feel you should not have to buy a number of
    lenses to compensate for the (probably temporary) high cost of
    manufacturing full frame sensors. I am inclined to put the 'extra lens'
    money towards something like a 5D and not buy lenses which may lose
    their usefullness over just a few years. The argument could go a number
    of ways depending on individual needs. In my case, I immediately
    cancelled my order for the Canon 10-22mm EF-S lens when I heard the
    first rumors of the 5D. Not saying I will go that way, but there was no
    way I was going to plunk down that kind of money for a lens I may not
    end up needing.
    winhag, Sep 26, 2005
  17. Paul Flackett

    Bill Hilton Guest

    One really wide lens would fix that problem quickly enough.
    True, especially if you are talking about fixed focal length lenses
    like in your example. But then over 90% of lenses sold are zooms ...
    Right, it's an 80 mm f/1.4 equivalent, which is a good deal when you
    consider the weight and cost of Canon's 85 mm f/1.2 L :) That's one of
    the points David and I were making, whatever you lose at the wide angle
    end you gain back at the telephoto end.

    In this situation I'd simply use the 35 mm f/2, which is very good
    optically and much lighter than the 50 f/1.4, plus is inexpensive (I
    have this lens and use it on the street with an 85 mm f/1.8, nice
    combination). Now you have a 56 mm equivalent plus a fast 80 mm
    equivalent so quit griping. Sure you lose one stop from the f/1.4 (go
    to the 28 mm f/1.8 if you really need the speed I guess) but a nice
    feature about digital is the ability to bump the iso up a stop when you
    need the extra speed.
    Canon will apparently be offering both 1.6 and 1.0x sensors for a while
    (plus the 1.3x of the 1D Mark II for a while longer) so pick a sensor
    size and stick with it if you're worried about shifting equivalent
    focal lengths, I guess. Most of us are coming from the 35 mm world
    where all our lenses were effectively 1x previously, so cameras like
    the 5D are just bringing us back to where we started, focal-length
    wise. So it's no big deal, except for those buying the EF-S lenses ...

    Bill Hilton, Sep 26, 2005
  18. Paul Flackett

    ASAAR Guest

    Thanks, I should have remembered that. I had a feeling that
    something would go wrong when I added "unless I'm making a
    calculation error somewhere", since at the time I could barely read
    the screen. Even now my eyes are nearly swollen shut due to some
    pollen allergy that started a little over a day ago. At least the
    headache/eye pressure is nearly gone. It would have been better if
    I'd have noticed microns != mega. :)

    As you noted, the 20D has 1.64 times the number of pixels for a
    given crop area, vs. my 1.94 (15.9/8.2) miscalculation. But that's
    still quite a large increase, very near to the difference in going
    from a 6mp to a 10mp sensor.

    I think you're going a little overboard here in trying to
    emphasize the superiority of FF sensors. The example under
    discussion was of using a long focal length to maximize the size of
    a bird's image. Do nature photographers often use apertures as
    small as f/16? I don't think they carry the excessive weight of a
    really good, large lens only to stop it down to a tiny aperture.
    And while as you say, the 5D ought to be less noisy, the difference
    in size between the 20D and 5D sensors is much less that the
    difference in size between notoriously noisy P&S sensors and the
    20D's sensor. So if the 5D is less noisy that the 20D, it probably
    won't be by nearly as large margin.

    This is true, but only if the total focal plane area can be used.
    As I said in my reply:
    If that wasn't completely clear, it implied that in such a case
    the 5D would be able to use the full frame (no cropping).

    But for this type of photography, often the full frame won't be
    able to be used, either because the bird is too small or too
    distant. When that's the case, the number of pixels used for the
    bird's image will quickly increase in the 20D's favor, reaching (as
    noted above) the same percentage difference as that between a 6mp
    and 10mp sensor. If cropping can be avoided though, the 5D would
    have a significant advantage.
    ASAAR, Sep 26, 2005
  19. Why thankee kindly Bill.And thanks everyone for your views. I think I'm going to have to stop
    worrying about whether I've bought the right equipment. I've been
    beating myself up for ages about about buying the Canon 400 f4 IS DO
    instead of the 500 f4 IS but then I just remind myself that it's about
    half the weight and I've probably taken it places hanging from my
    shoulder when I would have left the 500 at home.

    Not being a professional, (in fact I haven't made any money from
    photography at all yet) I can only afford one of everything!
    Paul Flackett, Sep 26, 2005
  20. Paul Flackett

    Skip M Guest

    Well, you pays yer money and you take yer choices, don't you?
    Skip M, Sep 27, 2005
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