DX V FX

[J.davis]

If i have my D750 and a new D7500, using the same lens/settings and using 1.5 crop in FX to the size of
the DX, in reality, should the DX give the better pic?
I would like to use the D7500 as a birding setup and D750 as everything else.
Any in depth comments welcome

[tandeejay]

I would have thought the DX would give a better pic in terms of pixel size of the image, as the FX would have to crop some of the image to produce the dx sized image

But given that the FX will have bigger pixel size on the sensor, it will have better low light performance, so that smaller pixel DX image from the FX camera might have better images in lower light

[arthurking83]

.....

But given that the FX will have bigger pixel size on the sensor, it will have better low light performance, so that smaller pixel DX image from the FX camera might have better images in lower light

and usually you'd get better dynamic range from the larger pixels D750.

That's usually true for when the technology is of the same era.
But technology moves on, so the devices in question need to be compared directly rather than use theories to describe hypotheticals.

No data exists yet on how well the D7500 handles dynamic range .. but the sensor it's using(from the D500) is very good, and maybe just a few percent better than the now old D750 sensor.
Looking at the DPR test results of the D500 vs the D750, I'd say that the D500 has a teeny bit more dynamic range, and that the noise at high ISO is too similar to judge one way or the other .. but D750 at high ISO is just a tad cleaner.

1. I wouldn't use the crop feature in camera if you're using a full frame capable lens(it makes no sense). Once you lose that peripheral data it's gone for good and you can't get it back.
2. I would just crop in PP to taste.
3. If you're focal length limited and really want that extra magnification of subject on your pixels, then you're better off getting the Dx camera.
4. once you crop the Fx image to an equivalent Dx framing composition, you're then limited with how much more you can crop(ie. you're already close to having cropped to 100% pixel size .. yet the Dx image being the same, can still be cropped a bit more.

if the comparison was say for a D800 vs D7000, when you crop the D800 image to Dx framing, it becomes the same size(close enough) to the pixel value as the D7000(about 15 or 16 Mp) .. so the argument back then was to go for the additional benefit that the Fx camera allowed.
But with the D750 vs D7500(using the D500 as a reference for the D7500), then the advantage is with the D7500, as it has more pixels at the same size format value(ie. 20Mp for the D7500, and about 12Mp for the D750 with a Dx crop).
So not only does the D7500 have the advantage that it allows for more cropping(8Mp more by comparison) .. if you view the entire image as a whole(ie. both at the same Dx format), as the D750 image is already cropped, the entire frame of the D7500 will look cleaner if high ISO noise was to be an issue in either image.

So! .. if Nikon were to make a new Fx camera with say 40+ Mp(as is expected for the D800 replacement) then this could/would change the result again .. probably back in favour of the Fx camera.

[Tannin]

PLEASE IGNORE MY GIBBERISH ABOVE, IT IS RIDDLED WITH ERRORS

THE FOLLOWING REPEATS IT WITHOUT MIXING UP "FX" AND "DX".

(Serves me right fror translating my post into Nikonese when I'm not fluent in that language. Ther terms "FX" and "DX" do not exist in my native Canonese language.)

(Perhaps some kind moderator could remove the part above. It's too late to edit.)










Broadly, yes. I'm not familiar with the particular models mentioned, but all else being equal:

For scenes where focal length is not a limitation, the FX will be better, but in good light the difference will often be so small as not to be worth mentioning. (E.g., a daylight landscape taken at 35mm on the DX and 50mm on the FX: not much in it.)

For scenes where you are able to fill the frame of the FX, the same applies. (Actually, this is just the first case described in a different way.)

For scenes where you have to crop the FX because you are focal length limited, it gets tricky. In perfect conditions, the DX will resolve more detail. Birding, that's no more than one time in three, maybe one time in five. In scenes where the light is marginal, the FX is king. And in-between, there is not a lot to choose.

I find that my 1D IV (APS-C, 1.3 crop) gives superior performance to my 7D (1.6 crop) more often than not. I always go for that one as first choice.

Where I need more reach, sometimes I add a 1.5 converter to the 500/4 for 700mm on the 1D IV; sometimes I use the 7D at 500mm. Both combinations give about the same reach. There really isn't much between them in terms of detail resolved. The superior handling of the pro body 1D IV tends to tip towards using that combo; on the other hand the shorter length and lower weight of the 7D without teleconverter is nice too. Summary: it's a wash.

Where I need even more reach, DX and teleconverter is the only option. Not worth doing unless the light is good, and generally not worth trying without a tripod unles the light is great. I may yet go back to using the 1D IV and a 2X converter. (The old 1D III and 2X combo was too slow to focus, but with a newer camera and the snazzy new model 2X converters ... who knows?)

Note that this is comparing with a by-now rather elderly 7D Mark 1, which for all its virtues is weak at ISO 800 and not worth bothering with at 1600. My new 7D II (paid for but hasn't arrived yet) is apparently much improved and very usable at ISO 1600. Your new DX body should be similar. So we may find that a current-generation DX camera is good enough to get more of the workload that the old Mark 1 managed. And, of course, we may find that a latest-model FX camera moves the goalposts. (If I can ever afford one!)

Finally, note that I'm comparing 1.6 crop to 1.3, where your question relates to 1.5 crop vs 1.0. I do have an FX camera, but the focus system on the 5D II is so primitive that it has never occurred to me to use it for birding. (The 5D II had, in its day, the best full frame sensor in the world - one so good that it's still excellent even now - but (alas!) the exact same low-tech focus system as the ancient 5D Mark 1, which was obsoleted by even most cheap consumer FX models (of any brand) in around 2005. All subsequent Canon FX cameras (and all Nikon FX cameras of any vintage) have vastly superior focus systems.)[/QUOTE]

[Cage]

Interesting question posed by the OP.

While I'm not going to try to give a definitive answer, if indeed there is one, I did play with some maths, partly for my own edification.

D7500 Sensor 23.5mm x 15.7mm 368.95 sq mm
Total Effective Pixels 20,900,000
Pixels per sq cm 5.6 MP/cm²
Pixel Area 17.46 µm²

D750 FX Sensor 35.9mm x 24mm 861.6 sq mm
Total Effective Pixels 24,160,256
Pixels per sq cm 2.8 MP/cm²
Pixel Area 35.4 µm²

DX Mode 23.5mm x 15.7mm 368.95 sq mm
Total Effective Pixels 10,346
Pixels per sq cm 2.8 MP/cm²
Pixel Area 35.4 µm²

After I'd done the above calcs I went looking for pixel sizes and came across this website whose numbers are close to mine, any slight difference possibly due to which of Nikon's published pixel count you chose to use.

http://www.digicamdb.com/compare/nik...vs-nikon_d750/

As you can see from the above the D7500 has about twice as many pixels per cm² of sensor size, so in theory should capture more detail. However the D750's pixels are twice the size enabling it to capture more light and maybe close to as much detail. Do some testing with both set-ups and go with what you deem the best for your requirements.

For birding, where the light is seldom ideal, I'd go with the D750 in FX mode, and crop in PP instead of using in-camera DX mode.

I should point out that a big factor in capturing fine detail is as much to do with what you mount in front of the sensor, as the sensor itself.

[Tannin]

I should point out that the biggest factor in capturing fine detail is as much to do with what you mount in front of the sensor, as the sensor itself.

Just so. And an even bigger factor is getting closer to the bird! Even an extra half-metre can make a significant difference if you can manage it.

[arthurking83]

.....

I should point out that a big factor in capturing fine detail is as much to do with what you mount in front of the sensor, as the sensor itself.

And this is probably the most important point to consider.

I've always been a believer in that just updating lenses because one is better than another isn't always the answer. But that it can be.
Like Tannin said, his full frame 5D can't focus as well, so there's no point in updating a lens onto a camera that can't focus as well, as focusing is probably the most important aspect when it comes to bird photography.

It's almost a dead cert that the D7500 will have a great focusing module, but almost as certain that it won't be as good as the D500(which it will share a sensor).

We know that a D7500 will come in at a retail of about $2K(AU), so we assume that you have $2K to play with.
Not knowing what lenses you generally tend to use, we could safely assume that it'll be something long .. and from memory the Sigma 150-600mm C comes to mind

So another way to look at is: for about $2K what other lens as an option to a new camera are available ... and what size/weight penalty could you accept as a consequence of such a new lens.

I noted that the Sigma 500mm f/4 OS HSM S retails for about $6500. Now that's way over your $2K camera budget, but if you sell another 'focal length limited lens' to help fund the new large Sigma lens.
Such an expensive lens is going to be an order of magnitude better than any zoom lens, and while it's 100mm shorter in FL compared to a 150-600mm, I think that number is trivial. A 1.4x TC mounted to the 500/4 is almost certainly going to achieve greater detail capture than the zoom lens at 600mm and wide open.
If you care to browse through The Digital Picture's lens comparison sets, choose the Sigma 500/4 at 700mm(they've used the 1401 Sigma 1.4 TC) and set the comparison lens as the Sigma 150-600 C, you'll see that the 500+1401 TC(giving 700mm) is sharper even wide open at f/5.6 than the zoom lens at 600mm, and even if stopped down to f/8.
Stop the 500/4 + 1401TC down to f/8 and you have a super detailed lens .. and for the price is a bit of a bargain!

Also note that you can snare a decently priced second hand Nikon 500/4 probably with VR, but an older generation and most likely well worn to boot .. but they're a solid lens and can take a bit of abuse.

Just some other options to consider.

[J.davis]

Thanks for the insights all. I used the old D300 for some shots and found the crop worked well, but the noise was VERY limiting.
I was looking at it from a crop factor. I usually crop to 1:1 as max and still get some good pics with my Sigma 150-600 C.
If I was to buy the D7500, I believe that I wouldn't have to crop as much.
Sound right?

[arthurking83]

....
If I was to buy the D7500, I believe that I wouldn't have to crop as much.
Sound right?

For a fixed situation, to achieve the same subject height within the frame of both formats, then yes, you're correct in saying that for the Dx format you wouldn't have to crop as much.
But that's because it's already cropped, and being so cropped it's also quite high resolution(ie. number of pixels for the format size).
So in this comparison if what you want is to crop less to increase the image size for the final image, then that's the way to go.


But if Nikon create an Fx camera with more than about 50Mp(or close too), then cropping images from that camera to Dx format size too is going to produce a similar image size compared to the D7500's crop format.
Remember it's about No. of pixels for a given format size, and the smaller the pixels, the greater then number of them for the sensor.
The Dx crop from Fx appears to be about 50% of the original Mp count of the Fx sensor .. or more accurately 42% or something like that.
So just for the sake of future reference, if we use that approximate formula, any future Fx camera at about 50Mp will produce a 20-ish Mp Dx crop.

[Cage]

As a follow on from AK's post I thought I'd throw in the D8xx's specs.

D8XX - FX Mode 35.9mm x 24mm 861.6 mm²
Total Megapixels 37.09MP
Pixels per cm² 4.22 MP/cm²
Pixel Area 23.72 µm²

D8XX - DX Mode 23.5mm x 15.7mm 368.95 mm²
Total Megapixels 15.4MP
Pixels per cm² 4.22 MP/cm²
Pixel Area 23.72 µm²

I dont know the co-relation between pixels/cm² and pixel size as far as detail gathering ability is concerned, but I suspect that in less than ideal light the bigger pixel would come out in front.

[Roane Photo]

I have found that a DX body is way better for birding as you pack way more detail into your shots so when cropping an image the final result is much better, sharper.

I think this video explains it better than I can https://www.youtube.com/watch?v=Hbli8lh9Pcw

[arthurking83]

I have found that a DX body is way better for birding as you pack way more detail into your shots so when cropping an image the final result is much better, sharper.

....

If the rumours are to be believed, and Nikon's next D800/high megapixel replacement has any more than about 54Mp, then the above situation will change.

Remember it's not just about the body, it's about the pixel density of the sensor in those respective bodies.

[Roane Photo]

If the rumours are to be believed, and Nikon's next D800/high megapixel replacement has any more than about 54Mp, then the above situation will change.

Remember it's not just about the body, it's about the pixel density of the sensor in those respective bodies.

arthurking you are correct when you say "it's about the pixel density of the sensor in those respective bodies." and that was my point, currently the pixel density of 20+mp DX cameras is higher than that of a FF camera however as you said a FF camera would need to be more than 54mp to come close to the density of a 20+mp DX. And as the OP was asking about specific current Nikon model DX and FF cameras I offered my opinion on those.

Believe me when the new Nikon FF is released and if it is in fact 54mp+ I will be seriously looking at purchasing one.

[jim]

arthurking you are correct when you say "it's about the pixel density of the sensor in those respective bodies." and that was my point, currently the pixel density of 20+mp DX cameras is higher than that of a FF camera however as you said a FF camera would need to be more than 54mp to come close to the density of a 20+mp DX. And as the OP was asking about specific current Nikon model DX and FF cameras I offered my opinion on those.

Believe me when the new Nikon FF is released and if it is in fact 54mp+ I will be seriously looking at purchasing one.

Well, the D810's 15.4 megapixel 7fps* DX mode isn't to be sneezed at for that matter.

*With Battery Grip.

[Roane Photo]

Well, the D810's 15.4 megapixel 7fps* DX mode isn't to be sneezed at for that matter.

*With Battery Grip.

I like how you add the battery grip lol.

[jim]

I like how you add the battery grip lol.

Well, I do add it. The camera balances better with my enormously long ... er, lenses that way

[Roane Photo]

Well, I do add it. The camera balances better with my enormously long ... er, lenses that way

Now your just bragging lol, but have to agree I have battery grips on most of my cameras (for the same reason of course)