FX cropped same as DX uncropped?

Discussion in 'Nikon' started by eric_m|4, May 4, 2016.

  1. If an FX camera and a DX camera have similar 24 MP sensor (such as a D750 and a D7200, or maybe even the newer D500) would an image from FX camera have the same detail as DX camera if FX image were cropped down to same size as the DX image? I know these cameras didn't come out at the same time and don't have same sensor but I was wondering if I was to shoot distant subjects, such as small birds, would I get a better image (more detail) with an FX cropped down so subject fills the frame or with a DX image that has subject filling the frame without cropping? Assuming lens, exposure, etc... was the same for both cameras. I'm thinking the DX format would be better for distant bird photography. Hope wording wasn't to confusing. Thanks.
     
  2. I'm thinking the DX format would be better for distant bird photography.
    That is correct. In cropping the photo from an FX camera, you lose megapixels, and thus detail.
     
  3. Unless you compare a new FX camera vs an old DX camera like a D810 vs a D70 otherwise in general the DX camera would yield better image.
     
  4. Think of it in terms of pixel density: The FX sensor has 24Mp spread out over a 50% larger area, for a lower density than the DX sensor with the same number pixels in a smaller area. Cropping the FX image to the same sensor size removes available pixels, making your 24Mp sensor a 16Mp sensor. The answer to your question is "no", a cropped FX image will not provide the same detail as an un-cropped DX image, all other things being equal.
    However, all other things are rarely if ever equal. The low light, exposure range, and other qualities inherent in the best FX sensors might well offset pixel density, if you shoot for them. Also, FX sensors are less sensitive to the vicissitudes of lower quality lenses, due to the lower pixel density.
    Because the DX sensor is smaller, it only "sees" the central portion of a full-frame lens' projected image, while still packing the same number of pixels into that area. It is this "crop effect" that makes the lens appear to have the same field of view, and thus magnification, as a 50% longer lens. For a given image, the DX sensor also gives more DoF. The combination of these two characteristics makes a modern DX/APS-C a good choice for wildlife photography, while acknowledging they still give something up to FX/full frame sensors.
     
  5. Since the D7200 is 24 MP and lacks an AA filter,whereas the D750 in DX mode is 10.67 MP and has an AA filter, the D7200 can record significantly more detail than the D750 in DX mode. There is no penalty in dynamic range because the D750 and D7200 are extremely similar sensors except for their size. This means that noise levels for D750 in DX mode are basically identical to D7200 (see this excellent site for comparison: http://www.photonstophotos.net/Charts/PDR.htm#). The D750 in FX mode with a longer lens will always beat the D750 with a 1.5x shorter lens though.
     
  6. David, above, is correct. I have both D800E (36mp) and D7100 (24mp) and have tried both ways with my Nikon 80-400mm AFS. For wildlife, the D7100 is noticeably better than the D800E cropped.
    Kent in SD
     
  7. Actually, the above math is wrong. An FX camera has
    2.25, not 1.5 times the area of a DX.
     
  8. How about comparing an FX camera with a 1.4x teleconverter to a DX camera?
     
  9. BUT, as suggested, you have to specify what 'generation' and density of sensor is present in any particular DX and FX comparison. You can't just compare all or any DX cameras to all or any old FX camera. etc.
     
  10. Actually, the above math is wrong. An FX camera has 2.25, not 1.5 times the area of a DX.
    Right. I assume David wanted to mean a 50% larger linear dimension, which means 1.5X longer format diagonal, thus with 1.5X larger width&height, -with the inherent area increase-.
     
  11. The real question is how you're using these photos. (Why does nobody ask that?)
    Printing at 16 x 20 or below? I can't imagine you'll see the difference between a D7200 and a D810 shot with the same lens where the D810 is cropped in.
     
  12. Peter--
    There is a difference. I've done it. For something like small birds especially, the DX wins.
    Kent in SD
     
  13. Kent, I totally respect you, but I'd definitely have to see that to believe it...

    Here's the thing, is it something you notice because you were looking for it? Would the crop "fail" as a photograph?
     
  14. Correcting and expanding on my math: A DX sensor is 24x16 mm, with a pixel density of 62.5/sqmm at 24MP. The FX sensor is 36x24 mm, with a pixel density of 27.8/sqmm at 24MP. Per these numbers, the DX sensor has a pixel density 2.25x that of the FX sensor. These densities have technical ramifications I am unqualified to describe. In response to the OP's original question, the baseline answer remains essentially the same.
     
  15. Let's keep the answer simple eh? And not drift off into pointless "area v linear wars" territory.
    As long as the lens is good enough (and most are), a native 24 megapixel DX sensor will beat an FF 24 Mp sensor cropped down. Pure and simple.
    There may be less noise in the FF image, but there'll also be a lot less detail!
    BTW, it's the linear dimensions that are important. Looking at area is a pure red herring and simply a by-product of multiplying two linear dimensions together. In the case of cropped FF and uncropped DX sensors having the same overall pixel count, the DX sensor will have 50% more resolution. For 3:2 ratio 24 Mp sensors the figures are: Approximately 125 lppmm (DX) as opposed to 83 (FF).
     
  16. What I meant to emphasize is that when we crop a
    24 megapixel FX image to DX area, we are not left with 16, but rather around 10.7 megapixels.
     
  17. 17mp dx crop from a D8xx compared to a 24mp DX - all thing being equal, it should be pretty much impossible to see a difference between the two.
    It would still be difficult to see a difference from a DX drop from a 24mp FX sensor (approx 10mp) compared to a native 24mp DX frame - there just isn't a huge real resolution difference. But ultimately the final print size must be taken into account.
     
  18. Oliver has his math right. Following the square law, cropping an FX sensor to APS-C size, divide by 2.25 (1.5^2, not 1.5). The result is a little less than 11 MP from a 34 MP sensor.
     
  19. Correction, "24 MP sensor"
     
  20. Come on Elliot. Do you really think there's no perceptible difference between a 10.7 Mp sensor and a 24 Mp one? I must have completely wasted my money upgrading from a D700 to a D800 in that case.
    There is no FF Nikon DSLR with the 54 megapixel sensor it would take to equal the resolution/pixel density of a 24Mp DX camera. With such a high resolution available, I can crop further from my DX D7200 to get wildlife shots unobtainable with any affordable lens on full-frame, and without the encumbrance of the heavy tripod capable of holding such a monstrous lens.
     
  21. Do you really think there's no perceptible difference between a 10.7 Mp sensor and a 24 Mp one?​

    If you print a billboard, there is a huge difference.

    If you print a 16 x 20, there might be a small difference.

    If you print an 8 x 10, there might be no difference.

    If you're just viewing on-screen as a jpeg, there is definitely no difference.
     
  22. Billboards have pixels the size of golf balls. At that rate, a 40' billboard might be only 1000 pixels wide.
    There is a decided difference prints 16"x 20" anyone can see at a glance. People can and do examine prints this size at reading distance. Titian or El Greco sized images are viewed at a distance, not just for security reasons. Even at 8"x 10" you have a better sense of detail and texture, but probably not in a wallet-sized print.
    High-quality JPEG images can have the same resolution, and usually have few if any noticeable artifacts even at the pixel level. You don't have as much room for adjustments in a JPEG, which is why 16 bit TIFF masters are better for a work in progress.
     
  23. It's nothing to do with printing billboard size, or even 20"x16". A 24 Mp DX camera allows shots like the one below to be taken with a modest 400mm lens rather than a much heavier and more expensive 600mm one.
    The below shot is a crop of around 1/4 frame from a D7200. Equal to filling a 6 megapixel sensor I suppose. Had I used my D800 with the same lens, it would have been as if I'd used a 4 megapixel camera. Only if I'd used a 600mm f/5.6 lens (that I don't own) would the shot from the D800 have equalled the D7200.
    From experience I know that the difference between 4 and 6 megapixels is significant on even a 10" x 8" print. So in short; it never hurts to have pixels to spare.
    Oh, yes, and I'd have had to stop the 600mm lens down further to get the same depth-of-field.
    00dvEF-562839784.jpg
     
  24. An FX crop will have a correspondingly smaller area, equivalent to the DX sensor size but you will lose out on MP.
    My D700 is my go-to camera for most stuff, but when I do bird photography, I will often go with my D300 as it gives me 1.5x greater magnification I need for closer images with no loss in maximum aperture as I would have with a TC.
     

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