Canon - Crop vs FF

Discussion in 'Photography Equipment & Products' started by prodigy2k7, Feb 11, 2009.

  1. prodigy2k7

    prodigy2k7 No longer a newbie, moving up!

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    I think Canon's crop bodies ahve 1.4x crop right?

    People say that a crop body is better for telephoto, but I disagree...
    That is only true for the same body, it depends on the body doesnt it?
    For ex:
    Body1: 10MP CROP
    Body2: 14MP FULL FRAME

    If you were to crop BODY2 image in photoshop, to 10MP, wouldn't it be the same?

    Or for another example...
    Body1: 20MP (FF)
    Body2: 10MP (crop)

    Wouldn't Body1 (full frame) actually be better for telephoto?

    This is all hypothetical...
    Basically, 10MP FF vs 10MP Crop, yes the crop is better for telephoto, but if the megapixel number for the full frame is high enough, it then becomes equal or full frame is better...

    I am not a very good explainer, but am I on the right track?
     
  2. Not sure what you mean.

    Not all pixels are created equal. If they both have 10 MP then the FF sensor has bigger pixels.

    More pixels means higher resolution... but also more "noise".

    Canon's crop is 1.6x

    There's a circle of light that comes into the camera at the back of the lens. Film sensors are square or rectangular (rather than round) so they can be lined up on a strip of emulsion. The "full frame" is actually the 24x36 size in millimeters of a 35mm roll of film. The cropped sensor is about 1/3rd smaller... or 1.6x larger to get back to full frame.

    If you have a full frame image, you can simply crop part of it, giving you the same as the cropped sensor would.

    That's all part of it, but I don't want to rehash the whole cropped sensor thing. It is NOT true that a cropped sensor somehow magnifies the effect of a lens... your lens (optically) does not become longer. It seems that way when you size images to the same format taken with a FF sensor.

    I dunno... hard to explain, but at some point you'll have an "Aha!" moment and then internalize the difference.

    One is not better than the other, use the tool that makes the most sense for what you're shooting. I shoot wide, so I prefer full-frame sensors, because the crop factor drastically affects a wide-angle's field of view.
     
  3. boomer

    boomer No longer a newbie, moving up!

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    I think i see what you're saying. when its in crop mode, you get that 1.6x conversion factor which in theory is better for telephoto lenses. But IMO, you could do the same thing with the FF full resolution picture in photoshop, crop it down, which also would give it the same effect of zooming in. the only benifit i see is the fact that it does the cropping for you? :-/ but you're loosing resolution that way.

    I think the main purpose of crop mode is so you can use a lens that's specifically designed for the smaller sensor cameras on a FF camera so you don't get that black ring.
     
  4. usayit

    usayit No longer a newbie, moving up!

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    The above clip is the key..... It really isn't all about sensor sizes as much as the density of the sensor sights. Given the same area and the same number of pixels, the results theoretically should be identical no matter what size sensor initially collected the data. More sensor sights more data BUT cramming more sensor sights into the same area will result in more noise.

    From a price point, crop sensors in consumer level cameras help keep cost down and bring a nice selection of cameras to market.

    The way I see it.. In good light (noise kept in check), the crop sensor provides an advantage to telephoto shooters with the added benefit of an sensor with a higher sensor density (more data) while sacrificing the FOV that wide angle shooters prefer.
     
  5. KevinUK

    KevinUK TPF Noob!

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    Hi,
    I looked into this myself a while back, its not a completely strange idea but with current cameras the maths and sensor capabilities don't add up in the right way. So, I agree with Iron Flatline, if i understand him correctly anyway.

    Firstly the crop on most canon cameras is 1.6 times, not 1.4, so its a little higher than you thought. Also 'megapixels' can be slightly misleading because they relate to the total number of pixels in an 'area' not linearly; e.g. to get double the resolution horizontally and vertically you need quadruple the total number of pixels. It comes down to resolution in the real sense - the number of pixels per inch must be the same or better in a full frame sensor to crop the image by 1.6 times and still match the resolution of a natively cropped frame camera, and although they have more pixels in total the pixel density is currently lower in canons full frame cameras.

    When I worked this out (no garantees of correctness!!) I calculated that a 5DmkII or a 1Ds mkIII would make an image of around 3450 by 2309 pixels if it were cropped and blown up to emulate the 1.6 times of a cropped sensor. A 50D natively has about 4750 by 3170, so would offer better resolution. Even the 40D and 1000D are still a little higher at about 3890 by 2590; only if you compare say a 5D mkII with an old 350D do you get to a similar resolution.

    That said, there are other issues than resolution. The main one for me would be that less densely packed pixels inherantly mean that there is space to have larger pixels (or i guess photo-receptors as its a sensor not an image). Generally speaking (and I too would rather not re-open the full frame debate) bigger pixels do tend to have a wider capacity for light levels. also less densely packed sensors are easier to design for lower noise.

    So I guess the over-all answer would be that if you're going to magnify by cropping (i.e. rather than optically with lenses) then a natively cropped-sensor camera would currently be better than cropping from a full frame image, particularly if image size/resolution were a priority to you. But, if you had to crop a full frame image (e.g. already had a full-frame camera) there are probably a few benefits in terms of latitude and noise that make this still a fair thing to do.

    If i were getting a canon camera specifically for telephoto work then I'd certainly go for a 50D over say a 5DmkII - even the 40D would be a favourite because its considerably cheaper and still arguably a better way of getting the 1.6 magnification. If i could afford it I'd go for 5DmkII and a bigger lens, but of course thats £never going to happen!

    Sorry - too many words again!!

    Kevin
     
  6. ksmattfish

    ksmattfish Now 100% DC - not as cool as I once was, but still

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    The magnification would be the same, but the complete photo from body 1 would be higher res than 14mp FF cropped to APS size. You need to compare sensor size, pixel size, and pixel density.

    Then again resolution may not be the most important consideration. Larger photo receptors can offer other advantages such as greater dynamic range (not always, but sometimes), and less issues with aperture diffraction.

    As far as noise goes big pixels are supposed to be the best when all other things are equal, but it does appear that a significant enough increase in resolution trumps big pixels.

    It would be best to compare specific camera models in specific situations to determine which would be better.
     
  7. Prophet

    Prophet TPF Noob!

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    Another issue with the bodies is data.

    A 5D and 1DS series cameras only shoot so fast. I think the 5D is under 4 fps.

    A standard 1D (mark I through III) while it is a 1.3 crop factor shoots at 8.5 or 8.3 FPS. It can pull the data off the sensor and put it into cache and further onto the memory card much faster than the full frame sensor.

    The 20D-50D series are 1.6 crop factors and only get betweet 3.5 and 6 fps. They acheive this speed because there is even less data to write to memory.

    Crop bodies are good for telephoto because their effective focal length is much longer. 200mm 1.6 turns into what 320mm? That is the only advantage. You then get into the whole pixel packing and noise issue. 40D is 10MP but has those pixel packed in much tighter.

    -JD-
     
  8. Do'Urden's Eyes

    Do'Urden's Eyes TPF Noob!

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    What is this crop mode that you speak of? theyre just smaller sensors. the reason the sensors are smaller is probably because theyre cheaper to produce and thus placed on most consumer/prosumer bodies. theres no switch on any camera that ive heard of to change a FF sensor into a cropped one.
     
  9. JustAnEngineer

    JustAnEngineer TPF Noob!

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    A Nikon full-frame camera (like the D700) can mount a DX lens. The camera will then use just the center portion of its sensor to record images, instead of recording the whole FX size image (which would have terrible vignettig outside of the center).
     
  10. frXnz kafka

    frXnz kafka TPF Noob!

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    Nikon's full-frame bodies to have a "crop mode" to allow you to use DX lenses on the FX bodies.

    But, we're talking Canon in this thread :er:
     
  11. prodigy2k7

    prodigy2k7 No longer a newbie, moving up!

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    Hmm, confusing subject, and I meant 1.6x not 1.4x thanks :p
     
  12. Samriel

    Samriel TPF Noob!

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    It's not really a confusing subject. The lens stays the same, the recorded image "changes" depending on the size of the film/sensor. For your question about the advantages of cropped sensors, I'll try to explain it with Nikon:

    We have the D300 and the D700. Both are 12MP, the first cropped (x1.5), the latter full frame. We have a 70-200mm f2.8 lens - on the D700, at 200mm the lens gives the equivalent of 200mm on 35mm film, that's why it's called full frame, as Iron Flatline already explained. On the D300, at 200mm the sensor records a field of view equal to 300mm if using 35mm film. At the same 12MP, the D300 gets a 1.5 times tighter crop, and is cheaper to produce, since smaller sensors cost less. Of course, noise and resolution is usually better with bigger sensors (D700) and you can stick more pixels inside effectively, but in some situations a smaller medium can have it's advantages. One of the biggest advantages of cropped sensors is camera size - all the compact (P&S) cameras are small because the sensor is small, therefore the lens can be smaller (doesn't need as much coverage) etc. If size wasn't important we would all be using large or medium format bodies for best quality.

    If you wan't to understand this on a more practical level, take a crop sensor lens and shoot a roll of film, or put in on a FF digital body without using it in cropped mode. It might help you more to understand things better. I suggest reading more on terms like focal length, lens coverage (image circle), medium (film or sensor) size and their relations to each other.

    To give you something to think about, on a 8x10" large format film camera (meaning the film/photo medium is 8x10", as compared to 24x36mm) a 300mm lens gives a field of view of a 50mm lens on a 35mm (FF) camera, while keeping the DoF of a 300mm lens.
     

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