D800 testing FF vs DX crop

Started Feb 24, 2014 | Discussions thread
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8pilot Regular Member • Posts: 107
D800 testing FF vs DX crop

In just under a week I'm heading off to the Centenary of Military Aviation air show at Avaon (Victoria, Australia).  I'm planning to primarily shoot airborne work with my 80-400, but figure even the 400 often won't give enough reach.  I ALWAYS shoot RAW only and fill the buffer on the D800 in just under 4 seconds on CH mode.  But I thought I'd experiment with the DX crop mode, as I figure I'll often be cropping anyway due to reach.  It then occurred to me I can probably also shoot "more in the same time" due to smaller file sizes and therefore quicker write to card time.  So, I just ran a quick test: D800 on tripod with 80-400, VR off, manual focus, CH mode, writing to a SanDisk 64G Extreme Pro SD card.

The basic question was: how many shots can each mode complete in 20 seconds of continuous shutter press?  How long it takes to finish writing to card, and therefore be ready to completely start again, was irrelevant to the test.

What I found was that the FF files averaged just under 79Mb, the DX crop files were just over 34 Mb, i.e. less than half the disk space size.

In FF, a total of 25 shots were completed.

In DX, a total of 42 shots were completed.

If you shoot FF and crop in PP to exactly the same as it would have been as DX you are essentially getting exactly the same thing right?  That is, the point at which you throw away unused pixels is at shutter press for DX, and in PP for FF?  Pixel-level data is no different, if my understanding is correct. Please teach me the error of my understanding if this is not right????

Further thoughts and questions: for those of you have either shot air shows, or perhaps other reasonably fast moving subjects (motor racing etc) how easy is it to keep the subject within the DX crop frame?  I'm very used to using the whole view finder and am concerned I might not frame shots well enough and end up slicing off noses or tails etc of aircraft.  Generally I prefer to shoot a little wide and then crop in PP to avoid that issue, but as I said I'm used to looking at the full view finder screen.

For ground static display shots where I can get reasonably close I'm highly likely to switch to the 24-70, although I might also take the 14-24.  I'm gonna have to remember to change back to FF if I use DX for ground-to-air shots!!  But then again, in other stuff I shoot I often could easily use a second body, so maybe splurging on a D7100 and putting the 80-400 on that (effective 120-600), and primarily use 24-70 on the D800 using the 14-24 when necessary could be a far better and functional????  All I'd be carrying extra is the one extra body. One thing I like of the D7100 over other DX bodies is it uses the same EN-EL15 battery as the D800, so I can take just one charger for both, and if I carry one spare battery between the two should probably do ok.

Another thing: D800 in DX crop mode give 4800x3200 pixels, D7100 in max resolution is 6000 x 4000.  Hmmmmm, thoughts to be processed …...

 8pilot's gear list:8pilot's gear list
Nikon Coolpix S9700 Nikon D800 Nikon D7100 Nikon AF-S Nikkor 70-200mm f/2.8G ED VR Nikon AF-S Nikkor 14-24mm f/2.8G ED +5 more
Nikon D7100 Nikon D800
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