DX vs FX

Discussion in 'Nikon' started by eric_m|4, Oct 23, 2013.

  1. At what point is DX format equal to FX format? For example, a D4 is a 16MB FX camera, at what point would a DX camera equal 16MB FX in detail/quality? Would it be 20MB? 30MB?... Assuming ISO setting, exposure, etc... is same on both cameras?
  2. Huh? A 16 mb camera is a 16mb camera.
    Kent in SD
  3. ShunCheung

    ShunCheung Moderator

    They are never equal due to many different factors, such as different lenses. That is why I use both formats depending on the particular application.
  4. As I understand it few could tell the difference in 97% of files. DX does a bit better in lower light. But that said, it is the photographer that makes the shot.
  5. Hi Shun,
    can you give an example? Thanks.
  6. ShunCheung

    ShunCheung Moderator

    For example, for any long telephoto work, I prefer DX because it gives you more reach. When your subject is small, you are simply wasting sensor real estate on FX.
    On the other hand, for wide angle work, IMO DX wides are not very good as they have to be very extreme 10mm, 12mm lenses, but those DX wides still have to clear the original flange-to-sensor distance Nikon picked for 35mm film way back in 1959. Additionally, wide tilt-shift lenses don't work well on DX bodies. For one thing they are no longer very wide due to the crop factor, and DX bodies with a pop-up flash tend to block the movement on such lenses. All Nikon DX bodies after the D2 series, which was discontinued in 2007, have a pop-up flash.
  7. DX does a bit better in lower light.
    That might be your experience....and maybe comparing D7100 to 5D (?). With high ISO's in D4, D800, D3s, D600/610 models....there are hardly any DX models that would be better. Anyway, what are you comparing to ?
  8. Eric: I ask myself the same question all the time, since I use DX bodies but am always looking to improve the quality of the images (not the art) in terms of better ISO performance, increased dynamic range, and low-light focusing performance since in my line of work, those are the most important qualities. I am also interested in pixel count, since we tend to crop a lot of our images and having more pixels to work with appeals to me.
    Here's a comparison of test shots from a D7000 and a D600. You can download the RAW files and pixel peep to your heart's content and decide if a) you can see a difference that justifies the cost of FX (lenses!) and b) there would be an improvement in your style of images. You can change ISO to see how the two formats perform on that metric.
  9. In rough numbers, a 16Mp DX would equal the center part of about a 25Mp FX camera. ( 16 * 1.6 crop factor ). So, the question might be, if I take the same shot with the same lens, but I need to crop and enlarge on the FX, and just enlarge on the DX to get the same field of view and picture size, which will give the better result ?
    I would guess that they would be equal. On the FX you're throwing away pixels the DX doesn't have and all else is equal.
    If I had the money, I think I would rather have the FX and the pixels to throw away and have a better wide angle possibility than use the DX which needs a 16mm lens to approximate a 24mm FX shot.
  10. DX does a bit better in lower light​
    actually, low-light performance on DX is the main reason i switched to FX. all things considered, DX is lighter, more compact, and a bit cheaper. at least that's the idea. The DX vs. FX debate has changed since 2007, with the addition of high MP bodies for both formats. one of the problems with DX is the prime lens situation -- the 1.5x crop factor means there's a dearth of wide-angle fixed-focal lenses, and 85mm portrait lenses arent in the sweet spot any more. another is that it will never do as well in hi-ISO as full frame. FX is also preferable when you really want a shallow DoF as you lose 1 stop with APS-C.
    But in terms of basic optic quality, i dont think FX has quite the advantage it was projected as having a few years ago. under certain conditions, yes. under all conditions, no.
  11. In rough numbers, a 16Mp DX would equal the center part of about a 25Mp FX camera. ( 16 * 1.6 crop factor )​
    That's a bit too rough with the numbers. The crop factor is 1.5 for Nikons (roughly), so to get the equivalent to a 16MP DX camera as the center portion of an FX camera, the correct calculation is 16*1.5*1.5 = 16*2.25= 36. Cue in the D800 and the D7000; the DX crop of the former equals the pixel count of the latter. Canon's crop factor is 1.6 - so the factor here is 2.56 and the equivalent FX camera would need to have 41MP.
    This also shows that the D7000 has no "more reach" advantage over the D800 - the pixel density of the DX camera and the DX crop of the FX camera is identical - there's just more surrounding area in the FX image. The 24MP of the D7100 provide more pixel density than the DX crop area of the D800 - and hence the "more reach" again applies.
    DX does a bit better in lower light.​
    From all I've read and seen, that's one area where FX shines.
  12. I got a D600 b/c the DX D7100 gap wasn't that much price difference plus also I still shoot FX film so no need to double up on the general mid lens.
    But in my subjective IMO, since I don't really shoot high ISO or need the wide angle lenses in FX like primes necessarily or the thinner depth of field DX is fine for me. I shoot most stuff at base ISO, f/11, LOL. I could shoot 4x5 or a 6x6 without electronics. DX cameras ISO have also improved a lot while not as good as FX they IMO suits most people.
  13. They are simply two different formats. As Shun and others say, some prefer one format for some applications, others differ.
    If you compare in the same generation of sensors, the quality of imagery should be very similar for both. Otherwise, the newer sensor will usually take the winner's cup, regardless of format size.
    I, too, as a rule use a DX for telephoto work and a FX for normal to wide. But sometimes I want the smaller body for walkabout, so use the DX for regular.
    Although I wouldn't have gone quite the direction I did, if I had planned it out ahead of time, I now have a full set of lenses (Ultrawide to tele) in both formats. Of course, the FX lenses can be used as longer equivalents on the DX too.
  14. What JDM said - it's two different formats, with different advantages and disadvantages. Making calculations to make some sort of equivalence is just a long and tedious way of ignoring those differences.
    For example, FX cameras have bigger viewfinders. Not that it affects the final file by a whole lot, but it is mighty nice. At equal circumstances (same focal length, same subject distance, same aperture - hence not the same image!), FX will have less DoF - and in this sense FX cameras can allow a bit more creative play if you like extremely shallow DoF.
    Only comparing the output of a camera is, in my view, pretty useless. It's part of a system, part of a tool that has to work in your hands and with your brain parked behind it. It has to have the lenses to support your ideas and needs (as noted, Tilt/Shift, wide angle primes, or affordable supertele reach on DX). So, leave the equivalence calculations behind, and get the right tool for your needs. All these DSLRs deliver good quality files, it's really the least of the problems.
  15. I shoot a D7100 and a D600. My wife shoots a D7000. There is no question in my mind that FX is better in low light. The D7000 is slightly older and the D7100 is slightly newer than the D600 yet the D600 easily has a one stop advantage. It is actually more, but "at least one stop" could not be considered controversial by anyone looking at the images.

    To answer the posters question... If by 'detail' you mean resolution all sensors of the same megapixel value have the same number of pixels. If you print the images the same size, say 8x10, from a 16mpx DX camera and a 16mpx FX camera both images will be at the same resolution.
    If by 'detail' you mean something else then newer tends to be better, and the glass is going to tend to matter more than the camera.
  16. An FX camera and lens behave extremely similarly to a DX camera with the same pixel count, a lens 1.5x shorter, at an aperture 1.5x smaller, with the ISO set 2.25x higher. The DX system is likely to suffer slightly more from pixel density requirements, and because most lens aberrations decrease as the aperture shrinks. The FX system with larger sensor sites may also have more dynamic range (in terms of free electrons per site). The DX system will likely be smaller, lighter and cheaper, although not by as much as you'd think if you scale the aperture properly. It seems to be easier - at least at longer focal lengths - to increase lens coverage than to increase the aperture. The rear point of an FX lens is less far from the sensor compared with the field of view than a DX lens - it can be less retrofocal - so it's easier to make good wide lenses.

    If you use the same relative aperture on both cameras, the FX camera will behave better at the same ISO, because the sensor is receiving more light in total. It will also have a different depth of field than a DX lens with the same relative aperture and equivalent focal length (i.e. a different lens). Adjust the apertures so the depth of field matches and you'll also have to adjust ISO (or shutter speed) to compensate. Put the same lens on two different cameras and, well, it's not the same photo any more, so I tend to see less value in that discussion!

    FX is not magic, but nor have Nikon produced a 135mm f/1.3 VR with optical performance that matches my 200 f/2 used on FX, so I'm aware that some options aren't available in DX.

    To make an FX camera act like a DX camera, add a 1.5x teleconverter (and adjust everything to compensate). That's effectively all the difference is, or at least 99% of it. Making a DX camera act like an FX camera requires a focal reducer; while these are available on some mirrorless systems, they probably won't be for DX any time soon.

    Differences such as the larger viewfinder view on FX can be implemented in DX as well - it's just that you need a larger aperture to get such a large image to appear as bright. If there were a lot of f/1.8 zoom lenses available for DX, DX finders would probably be bigger and brighter. The current DX finder has to account for f/2.8 lenses being darker than f/4 lenses used on an FX camera, which means that big magnification corresponds to a very dim image.
  17. There's a saying - "Horses for courses" - that sums this up almost completely. In other words the DX format has the advantage for some types of subject, and FX for others. Pixel count is pretty much a complete non-consideration in the comparison.
    DX has the upper hand for most sports and wildlife, due to better 'reach' with a telephoto lens, and because the smaller mirror and shutter are capable of a higher frame rate. It also excels at macro work due to the higher magnification possible and its greater depth-of-field for any given field of view and subject distance.
    Full frame excels at control over depth-of-field, better availability of wideangle lenses with lower distortion, better low-light and noise performance and generally better image quality. The viewfinder image is bigger and brighter too.
    Obviously you have to compare like-for-like, and a full-frame camera fitted with a cheap superzoom is going to be no match for a DX camera fitted with a high-aperture prime or professional quality zoom. And FWIW the advantages of DX are rapidly being eroded and exceeded by the even smaller formats of high-quality mirrorless cameras. However, the reasons for using different format sizes really haven't changed since the days of film; when a professional would choose 35mm, rollfilm or large format for a job depending on its demands. All that's happened is that those formats have all scaled down a step or two.
  18. Rodeo, your statements "Pixel count is pretty much a complete non-consideration in the comparison" and "DX has the upper hand for most sports and wildlife, due to better 'reach' with a telephoto lens" kind of contradict each other. When a DX body has more 'reach' over FX, it is specifically because of pixel count.

    This statement is also not quite correct, "DX has the upper hand for most sports and wildlife, due to better 'reach' with a telephoto lens, and because the smaller mirror and shutter are capable of a higher frame rate" I don't think there are many (or any) DX cameras that have a higher frame rate than a D3, D3S or D4, all of which are FX bodies.

    In response to the OP's question "At what point is DX format equal to FX format", I think the answer is it won't assuming you are comparing the latest DX to the latest FX models.
  19. Best in low light? Easy.
    Let's compare a "Nikon" 24mm DX sensor with a 24mm FX sensor. The FX sensor has an advantage in dim light. Here are the actual figures from DXOmark. The 24mm FX (D610) is 2925 ISO. The 24mm (D7100) is 1256 ISO. The D610, having larger pixels, is able to gather more light. http://www.dxomark.com/Cameras/Comp...brand)/Nikon/(appareil2)/865|0/(brand2)/Nikon
    This is pretty much accepted fact!
    To answer the OP question, I can't. There are too many variables.
  20. Steve, I guess you mean 24 MP DX sensor with a 24 MP FX sensor?
    mm's got me real confused!!
  21. Steve: If you compare across the whole frame capture area, at the same f-stop (which determines the amount of light hitting the sensor per unit area, indirectly), and ISO (response to amount of light falling on the same area), a larger sensor will handle low light better than a smaller sensor because more light is hitting it. At the same f-stop, assuming that your lens length was scaled by the crop factor so that you're capturing the same field the larger sensor also has a smaller depth of field. Stop down to correct the depth of field, up the ISO to correct the exposure, and the differences mostly go away. There's nothing magic about the FX sensor that gives it low light performance - take the same image (including depth of field) using a crop sensor (by using a wider aperture) and the "low light advantage" disappears.

    If you consider it pixel by pixel, the pixel area matters. Since the days of gapless microlenses, it doesn't matter much - you can pretty much downsample a high resolution image and get a good match to the output of a lower resolution sensor. Comparing pixel by pixel isn't usually all that relevant. For "reach", it's the pixel density that matters, not the sensor area: a D800 has more "reach" (smaller pixels) than a D300, because its sensor sites are smaller, despite having a bigger sensor. You can always crop the centre out of a D800 image to prove this. It's just usually been the case that crop-sensor cameras have smaller sensor sites than full-frame ones.

    There are technology generation differences as well, but most recent cameras are pretty near equal once you balance the areas out.
  22. Mike . . . excuse my typo! :) Of course I meant MP as opposed to MM. It was late. Thanks for the correction. Whew.
  23. ShunCheung

    ShunCheung Moderator

    Actually, both the FX and DX sensors have a 24mm edge. While the exact dimension varies a bit, FX is 24x36mm while DX is 16x24mm. Therefore, referring to them as 24mm is not entirely wrong. :)
  24. Shun, have you ever considered a career in politics?..:)
    Steve, I was thinking that's how big the long axis of the DX crop 'within' an FX D600 chip is and was definitely over-thinking it! DxO might do something that weird?
  25. Making a DX camera act like an FX camera requires a focal reducer; while these are available on some mirrorless systems, they probably won't be for DX any time soon.​
    More like never. Focal length reducers live in the gap between the larger flange distance for a lens designed for a larger-format camera (normally an SLR) and the smaller flange distance designed for a smaller-format camera (generally mirrorless). Since FX and DX lenses go on cameras with the same flange distance, the focal length reducer to use FX lenses on DX cameras would need to have a thickness of zero. Let me know when you find this optical design for me; if it works well we'll split the profits. ;-)
    Seriously, focal length reducers could have been developed to mount SLR lenses on rangefinder cameras, but then the lenses would not be coupled to the rangefinders. No point in that, especially since the reduced image circle would not have covered the film area. They also could have been developed to put medium-format lenses on 35mm SLRs, but there really wasn't a point in doing this either, at least not enough to justify the expense of the needed R&D for the precision optics required.
  26. I use Nikon DSLRs because, I have quite few lenses from the film days, and they work or can cheaply made to work on the digitals. I bought a D70 in 2004, the only bought brand new, because the price was fairly reasonable. Since then, I bought a D200, now converted to infrared, a D90, a D300, a D7000, and finally a beloved D700 FX. The Megapixel war will be fought till the end of time, but as an amateur enthusiast, 12 Meg's suits me fine, since I never print larger than 12x18 inches. I am in my 70s, and I think my DSLR buying days are over. I am still buying ancient film cameras when. I see a good one. There was much discussion of reach in this thread. If this is really important, I urge you to try some of the super zooms in $300-500 range made by Canon, Nikon, Fuji and Panasonic. They are really quite good. The have lenses to 1000- 1200mm.

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