I have a full frame camera (Nikon D-810) and a tele lens (Nikon 70-200mm) and want to use it as my first experience in a fashion runway show.

It is not like I want a full frame to capture a landscape that full frame helps me better — I just want to shoot a little square area that model stands in there. So I was thinking if I switch the camera to its "DX mode" then 200mm becomes almost 300mm with crop ratio. Do you think that is beneficial to me in this specific use case? Or, are there other things that I will miss and I am not aware of?

  • \$\begingroup\$ You'll lose all teh bokeh! \$\endgroup\$
    – BBking
    Mar 17, 2015 at 4:07
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    \$\begingroup\$ You're not losing bokeh! Switching to DX is essentially just digitally crops the image - a thing that could also be done in post-processing (just like the answer suggests). \$\endgroup\$
    – Ghanima
    Mar 17, 2015 at 10:10
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    \$\begingroup\$ When you print the DX image the same size as the FX image, you are changing the ratio of the size of the virtual image projected on the sensor to the size of the print - and therefore you will change the Depth of Field because changing the magnification ratio will change the largest circle of confusion (on the virtual image projected on the sensor) that will be perceived as a single point on the print. Another way to put it is that when you print the DX image the same size as the FX image you have magnified the blur in the image 1.5X larger and have thus reduced the DoF. \$\endgroup\$
    – Michael C
    Mar 18, 2015 at 0:07
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    \$\begingroup\$ The same thing happens if you print the same image at two different sizes and then view them at the same distance: A 16x20 print of the same image viewed at 10 inches will have narrower DoF than an 8x10 print of the exact same image when viewed at 10 inches. If you then trim the 16x20 image to leave only the center 8x10, you have doubled the magnification of the image and cropped to only the center 1/2 of the original image. \$\endgroup\$
    – Michael C
    Mar 18, 2015 at 0:11
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    \$\begingroup\$ Please see photo.stackexchange.com/a/38336/15871 \$\endgroup\$
    – Michael C
    Mar 18, 2015 at 0:27

1 Answer 1


Your 200mm will still be a 200mm. It will project the same image on the sensor. In DX mode, all that will happen is the camera will throw away the outer areas of that captured image and retain what would have fallen on a DX sensor. This is something you can do yourself in post-processing, so I don't think there is much benefit (apart from smaller file sizes and quicker write times to the card)

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    \$\begingroup\$ +1 From my experience at a couple of runway shows the locations available to photographers favoured a 70-200mm FX anyway. From where the press pack were located the 70mm on the DX body I was using wasn't quite wide enough to give enough breathing space to the classic full length end of runway shot. \$\endgroup\$ Mar 17, 2015 at 11:14
  • \$\begingroup\$ @JamesSnell thanks, great to know that. Will see how it goes this weekend \$\endgroup\$ Mar 18, 2015 at 2:16

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