DX on FX comparison

kingjonesy

kingjonesy

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Rich
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Hi all,

I've been testing a few camera lens combinations and pixel peeping...

Cameras tested: D610 + D7100
Lenses tested: 35mm 1.8G DX, 17-55 2.8 DX

So I've taken a photograph from a tripod (which hasn't moved) using flash (TTL), camera settings have been the same throughout (RAW, 1/250, 1.8 or 2.8) on each camera with each lens. I've not used the DX crop on the D610. On the zoom I've zoomed to match the same zoom as the cropped 7100 (~19mm).

I was expecting to get very similar results e.g. compare the ~19mm zoom on the 17-55mm using the D610 as the image produced on the 17mm zoom on the D7100.

However, the D7100 is sharper, more contrast, more detail than the D610. Bokeh is more "creamy"/even on the D610 but is far softer.

Is this expected using this combination of FX body with DX lens or simply down to the pixel density?

Has anyone else done any similar tests with different results?
 
Not that I know what i'm talking about but I used the same term 'creamy' when I first used a d700 against the d7200.
That was with a 300mm and 150-600mm though.
 
kingjonesy said:
Hi all,

I've been testing a few camera lens combinations and pixel peeping...

Cameras tested: D610 + D7100
Lenses tested: 35mm 1.8G DX, 17-55 2.8 DX

So I've taken a photograph from a tripod (which hasn't moved) using flash (TTL), camera settings have been the same throughout (RAW, 1/250, 1.8 or 2.8) on each camera with each lens. I've not used the DX crop on the D610. On the zoom I've zoomed to match the same zoom as the cropped 7100 (~19mm).

I was expecting to get very similar results e.g. compare the ~19mm zoom on the 17-55mm using the D610 as the image produced on the 17mm zoom on the D7100.

However, the D7100 is sharper, more contrast, more detail than the D610. Bokeh is more "creamy"/even on the D610 but is far softer.

Is this expected using this combination of FX body with DX lens or simply down to the pixel density?

Has anyone else done any similar tests with different results?
Click to expand...
I'm not exactly sure what you've done in terms of setup and focal length tbh as it's not too clear? However, all things equal the FF should be sharper. Pixel density actually puts more demands on the lens and so reduces sharpness. I've done tests recently comparing my D750 to the D7200 using the same lens and framing the same (this required the tripod to be moved closer to the subject using the D750 obviously). I've even done the same using DX mode on the D750 to match the D7200 framing without moving the tripod. The D750 was better when using full resolution, and I think it was better as well in DX mode when viewing in full screen.

If you do tests like this use liveview to remove any focus inaccuracies as you're findings might be due to front/back focussing. As for the bokeh, the characteristics of the lens should be the same but depending on how you've framed them it may differ. If you don't move the tripod and therefore frame differently between them the DX will actually have less depth of focus due to the extra effective focal length.
 
Thanks for the replies.

Sorry, my explanation wasn't that clear, having read it back it confused me!

The tests I did kept the camera static and zoomed the lens to adapt to the difference in crop. I see what you mean re dof differences and I also notice my focus (using live view) wasn't that accurate. I think I'm going to repeat the test but using a simple grid/lines as a subject to photograph. I'll move the tripod and mark the framing more accurately as well.

the reason I'm doing this (should have said in my original post, sorry) is that I'm trying to work out if I should use my wide lenses on my FF body or not, and if not, should I therefore buy a wide fast prime for the FF.
 
If your wide lenses are for a crop format then yes, you should buy a FF wide to benefit from the extra sensor area.
 
kingjonesy said:
Thanks for the replies.

Sorry, my explanation wasn't that clear, having read it back it confused me!

The tests I did kept the camera static and zoomed the lens to adapt to the difference in crop. I see what you mean re dof differences and I also notice my focus (using live view) wasn't that accurate. I think I'm going to repeat the test but using a simple grid/lines as a subject to photograph. I'll move the tripod and mark the framing more accurately as well.

the reason I'm doing this (should have said in my original post, sorry) is that I'm trying to work out if I should use my wide lenses on my FF body or not, and if not, should I therefore buy a wide fast prime for the FF.
Click to expand...
I missed that they were DX lenses :facepalm: DX lenses aren't great on FX bodies and I personally wouldn't use them on FF. I know some do but for me IQ's not going to be great, and by the time you've cropped out the vignette you've lost a lot of resolution.

FYI focus in liveview should be accurate (for static subjects), in fact more accurate than the phase detect system used when looking through the viewfinder.
 
kingjonesy said:
However, the D7100 is sharper, more contrast, more detail than the D610.
Click to expand...
Before spending much money you need to rent or borrow a feasible full-frame wide (ideally the one you're going to buy) and try it on your particular D610 ... it may well give softer results and I'd hate for you to find that out after buying an expensive lens ...
 
I've used a sigma 12-24mm mk1 on the d610 for fx (certainly not the sharpest) it helped me realise just how much more wide angle I can get out of a full frame, coming from a dx nikon d90
 
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