1.5X Sensors VS. Full Frame and other questions...

Discussion in 'Digital Photography' started by Progressiveabsolution, Apr 27, 2006.

  1. What exactly does the 1.5X crop do to the image that is produced from
    the camera? In other words, does it degrade the quality of the picture
    when comparing to a full framed camera body?

    What is the essential difference in image quality between a full frame
    body and a 1.5-1.6X cropped body?

    How much of a difference is there in image quality between the full
    frame body and the 1.5-1.6X sensor bodies?

    I'm sure this has been answered but hopefully I can get some more info
    on this.

    Thanks all for your help!
    Progressiveabsolution, Apr 27, 2006
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  2. Progressiveabsolution

    David Guest

    Full frame with the same lens will have a shallower depth of field than the
    1.6 for the same 'framed' photo. Which is better for isolating the
    foreground from the background (out of focus background).

    1.6 gives you a longer focal length. So, longer at the telephoto end, but
    shorter at the wide angle end (not as wide with the same focal length, but
    longer with the same focal length).

    1.6 gives you more distortion at the wide angle as a 17mm lens is still 17mm

    Vignetting maybe reduced on a 1.6 as the true edges of the lens is wider
    than the sensor (unless a EF-S maybe). Although 17mm EF-S wide open on a
    1.6 body can still give vignetting.

    Full frame has less noise, so you can shoot at a slower ISO/noise ratio.

    Full frame has a better range of 'L' lenses available. There isn't a 24-70
    equivelent for 1.6 cropped cameras. However, there isn't a 112-320 'L' lens
    for full frame bodies either.

    So, what you are asking is should I go for a 30D or a 5D? Full frame is
    better than 1.6, if you have plenty of money to spend. Disadvantage is you
    don't have such a good focal length at the telephoto end, but if the sensor
    has more megapixels, then you can always crop the image afterwards to give
    the same result. Also, the 5D lacks in the FPS section.
    David, Apr 27, 2006
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  3. Progressiveabsolution

    railfan Guest

    Not really. The digital sensor is 60% as large as a 35mm frame.
    Therefore it only sees the middle 60% of a lens' view. It gives the
    size of a longer lens, but not the magnification. A 300mm lens on a
    digital camera will give the same magnification, but just the 60% of
    the image, giving the impression of a longer lens.
    A digital sensor with a 17mm lens sees only the 60% center of the
    image, resulting in the field of view of a 28mm lens. No disortion

    B. Boudreau
    railfan, Apr 27, 2006
  4. Progressiveabsolution

    David Guest

    I appologise for not spelling it out, however I did say later 'but if the
    has more megapixels, then you can always crop the image afterwards to give
    the same result'.
    Try shooting vertical buildings with a 17mm on a 1.6 sensor.
    David, Apr 27, 2006
  5. It means the sensor is only seeing a portion of the image produced by
    the lens that a full size sensor would. It means that to get the same
    coverage a lens will need to have a smaller focal length.

    The amount of information the sensor can record is more of a factor of
    the pixel count than the size. (Note: in some ways the larger sensor can do
    better but since there are other factors to consider, I would not worry
    about that, just look at comparisons of real images from any lens-camera
    combination you are considering.) .
    Joseph Meehan, Apr 27, 2006
  6. actually .... " at a higher ISO/noise ratio."

    That amounts to you can use higher ISO settings and get less noise than the
    smaller sensor cousins.
    Thomas T. Veldhouse, Apr 27, 2006
  7. Progressiveabsolution

    Alfred Molon Guest

    ....and worse when you need a lot of DOF, for instance for landscape or
    architectural shots. To get the same DOF with the full frame lens you
    will need to stop down the lens and might have to use a higher ISO
    resulting higher noise levels.
    Alfred Molon, Apr 27, 2006
  8. Yeah, especially when those pesky buildings don't merely sway, but start
    to dance around. Note: Always shoot mountains at 1600 iso in case they
    erupt, or jump causing blur at 1/2000.
    John McWilliams, Apr 27, 2006
  9. This isn't true. The noise and the DOF scale in the same way, so at the same
    pixel count, same shutter speed, same DOF, the noise is the same. This is
    because statistical noise is reduced by sqrt(2) when you double the area of
    the pixel, and is also reduced by sqrt(2) when you divide the ISO by 2.

    But in real life, ISO 100 at f/16 for a sunny day landscape has a shutter
    speed of 1/100, which is plenty either for landscapes or telephoto with IS.
    And if you are serious about image quality, you use a tripod. And maybe a
    T/S lens.

    Also, while the DOF _at the same f stop_ is much wider for small sensor
    cameras, the _maximum DOF obtanable with decent sharpness_ is exactly the
    same, since the effects of diffraction scale as well.

    In real life, 5MP 2/3" dcams had best sharpness at f/5.6 or f/6.3. Pack more
    pixels into a smaller sensor and even f/5.6 will be problematic due to
    diffraction, so you are stuck shooting at f/4.0.

    David J. Littleboy
    Tokyo, Japan
    David J. Littleboy, Apr 28, 2006
  10. Progressiveabsolution

    Alfred Molon Guest

    How funny. There might not be enough light for a handheld shot at F16-
    F22, both outdoors and especially indoors. Stop down the lens and you
    get very quickly exposure times in the range of 1/20s or longer, if it's
    not a bright and sunny day.
    Alfred Molon, Apr 28, 2006
  11. Progressiveabsolution

    Bryan Olson Guest

    Exactly that; no more, no less: it capture a smaller part of
    the lens' image circle, by a factor of 1.5, both horizontally
    and vertically. In terms of area, it captures the center-most
    44.4% of what a 35mm full-frame sensor would capture (39%
    for a 1.6X crop-factor).

    Other effects often attributed to the crop are fictions of
    convenience. They are actually caused by other changes made
    to compensate for capturing the smaller field of view. For
    example, in order to put the same scene in the smaller frame,
    we would use a shorter focal length, by the same factor of
    1.5. To make a print of the same size from the smaller sensor,
    we necessarily apply more enlargement (from capture to print),
    by that same factor.

    A lens that has a focal length of 50mm on a full-frame
    body will still have a focal length of 50mm on a 1.5X-crop
    body. The 1.5X-crop body will simply capture a smaller part
    of the image formed by the lens.
    Those questions are too general to admit an exact answer.
    For one thing there are several full-frame bodies and many
    1.5-1.6X-crop bodies. Fortunately there are many comparisons
    and examples available on-line.
    Yes, and some of the many answers on this issue have even
    been correct.
    Bryan Olson, Apr 28, 2006
  12. Hah! I knew you'd be dour.

    Ah, architecture shots in some schools are outdoors, vs. "interior"
    shots. Landscapes do tend to the out of doors, world wide. For all three
    types just mentioned, I often use a tripod regardless of shutter speed

    Or did you merely forget to mention hand held in the post I replied to
    prior to this?
    John McWilliams, Apr 28, 2006
  13. Progressiveabsolution

    Mark² Guest

    The lens still projects a full-frame image...its just that the sensor only
    sees the middle portion of it due to the sensor's size being smaller than
    the full-frame projection. Think of it as a slide projector projecting a 6
    foot wide image onto a 5 foot wide screen. The projected image stays the
    same...you're just not catching all of it on the screen.

    Because of this, image quality is not changed at all...rather, you are
    simply (in effect), utilizing all your sensor's pixels on the "sweet spot"
    of your lens. Some see this as an advantage due to decreased vignetting and
    the use of only the sharpest portion of the lens. Others who want wide
    angle may not like losing the wide angle of view they are used to...
    Mark², Apr 28, 2006
  14. Ah, but you are enlarging the sweet spot 1.5x times more. So the question
    becomes: is the center section of a 35mm lens really 1.5x times better than
    the whole area of a 50mm lens.

    Since the 35mm lens is designed to cover 24x36, it's a much wider angle lens
    than the 24x36 50mm lens, and is going to have _worse_ performance, not 1.5x
    better performance. Even comparing a point, say, 10mm off axis on the 35mm
    lens with a point 15mm off axis on the 50mm lens.
    The decreased vignetting _wide open_ comes at the cost of reduced
    resolution/contrast. It's really hard to make wide angle lenses, and for
    lenses with an 80mm or wider FOV, cropped cameras with legacy lenses are a
    bad idea.

    The good news is that this effect doesn't apply to telephotos. But
    telephotos (other than cheap consumer zooms) don't have a sweet spot,
    leaving you with the 1.5x greater enlargement penalty. Oops.

    The idea that a smaller sensor is better flies against 150 years of
    photographic common sense, and is simply nuts.

    David J. Littleboy
    Tokyo, Japan
    David J. Littleboy, Apr 28, 2006
  15. Progressiveabsolution

    Skip M Guest

    Here's the most graphic example I could find of the difference between a
    1.6x crop camera and a full 35mm frame:
    Skip M, Apr 28, 2006
  16. Progressiveabsolution

    Mark² Guest

    By "image quality," I was referring to the image cast on the sensor. The
    degree to which one chooses to enlarge that will determine the extent to
    which its flaws become visible...right?

    You could also say that you are enlarging any flaw by 1.5x.
    If I implied otherwise, I didn't mean to.
    Don't interpret my post as proposing any such assertion as to necessitate
    your last sentence, there...
    I'm very close to lightening my wallet on the 5D...

    Mark², Apr 28, 2006
  17. Yes. But I generally assume that one is making the same size prints from
    I was more arguing with the "sweet spot" theory in general than anything you
    said in particular.
    You made the mistake of using the term "sweet spot" without explicitly
    criticizing it, which is like waving a red flag in front of a bull...
    You'd better hurry. My pet dSLR theory is that the beasts have an 18 month
    product cycle, and if one isn't interested in early-adopter pain and
    problems, then 6 months after introduction is optimal. If you wait 12
    months, then the next great thing will be announced almost immediately.

    By the way, don't I still owe you dinner? If you're going to be in the
    Boston area June 5 to 11, you could collect. (But aren't you one of the West
    Coast crown???)

    David J. Littleboy
    Tokyo, Japan
    David J. Littleboy, Apr 28, 2006
  18. Progressiveabsolution

    Mark² Guest

    Ya...I should have known better. Your techno-speak definitely out-shines
    anything I have the patience (or math/physics background) to build a
    sentence around...... ;)
    Yes you do, as a matter of fact!
    I'll be stuck on the west coast in June...but I'm thinking maybe I should
    hold off on collection...and instead wait until I win a few more bets...so I
    can COMBINE them into a plane ticket to Japan...where you'll be obligated to
    provide the original dinner...and...grand tour of the island. :)
    --I'm thinking that should take in the neighborhood of 50 bets won.
    At the rate we bet...I should reach Japan in approximately 50 years.
    By that time, we'll both have scant few teeth, and likely little interest in
    dinner that requires chewing.
    On second thought...I think I'll take that dinner now, thanks!
    See ya in Boston!

    Mark², Apr 28, 2006
  19. Progressiveabsolution

    Alfred Molon Guest

    Even outdoors there might not be enough light for handheld shots at F16
    or F22. Not everybody lugs around a tripod all the time, do you?
    Alfred Molon, Apr 28, 2006
  20. Progressiveabsolution

    Mark² Guest

    Most folks serious enough to buy full frame DSLRs are serious enough to use
    a tripod for landscapes.
    If you don't care to use a tripod, there is a very good chance that you
    won't be making very good use of full frame resolutions. At that
    resolution, you need every bit of lens/steadiness sharpness you can muster.
    Otherwise, you may as well not bother...unless the only care is a wide angle
    of view.
    Mark², Apr 28, 2006
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