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DX vs FX

eric m , Oct 23, 2013; 07:49 p.m.

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?


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Kent Staubus , Oct 23, 2013; 07:55 p.m.

Huh? A 16 mb camera is a 16mb camera.

Kent in SD

Shun Cheung , Oct 23, 2013; 07:56 p.m.

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.

Errol Young - Toronto, ON, CA , Oct 23, 2013; 07:57 p.m.

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.

eric m , Oct 23, 2013; 08:10 p.m.

Hi Shun,
can you give an example? Thanks.

Shun Cheung , Oct 23, 2013; 08:21 p.m.

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.

Leszek Vogt , Oct 23, 2013; 08:33 p.m.

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 ?


Peter Cohen , Oct 23, 2013; 09:02 p.m.

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.


John Williamson , Oct 23, 2013; 09:10 p.m.

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.

Eric Arnold , Oct 23, 2013; 09:17 p.m.

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.

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