"Crop-ability" of images?

Started 3 months ago | Discussions thread
john isaacs Veteran Member • Posts: 5,885
Re: "Crop-ability" of images?
2

dperez wrote:

More photographers who’s judgement I respect are talking about moving to Olympus. A question came up the other day and I’m trying to figure out the answer.

Nikon D850, 600mm f/4 versus M1X, 300mm f/4.

As I understand it - the lenses are the same equivalent - 600mm. The Nikon shoots at f/8 and ISO 3200 and 1/500. The M1X shoots at f/4 so the DOF is the same, and ISO 800 and 1/500, so the exposure is the same, right?

Go outside and shoot a backyard bird. Same spot, same distance, same bird, both cameras.

On EACH sensor does the bird take up approximately the same percentage of the sensor? On the D850 image the bird’s head covers about 20% of the width of the sensor. Does the bird’s head cover the approximately the SAME 20% of the sensor on the M1X – within reason since one is a 3:2 sensor and the other is a 4:3 sensor?

If SO, the bird’s head is 20% of 5184 = 1037 px on the M1X and 20% of 8256 = 1651 px on the D850. Based on that, the subject in the D850 image has 60% more pixels available for cropping. What am I missing?

The only thing missing is the justification for shooting at f8 with an f4 lens.  The f4 lens will have more precise focus due to the wider aperture (and narrower DOF).  But you really need to calibrate AF with super-telephoto lenses on a DSLR.

A better comparison would be to use a 500mm f5.6 PF, which saves thousands of dollars and plenty of kg, and use some of the excess pixels on the D850 to adjust for the wider FOV.

The plus is that it is easier to get and keep a 500mm lens on target versus a 600mm lens.

 john isaacs's gear list:john isaacs's gear list
Panasonic Lumix DMC-GH4 Nikon D750 Olympus E-M5 II Nikon D500 Olympus E-M1 II +16 more
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