Depth of field question- Crop / Full Frame

Started 5 months ago | Discussions thread
bobn2
bobn2 Forum Pro • Posts: 58,551
Re: Depth of field question- Crop / Full Frame
1

Pk8887 wrote:

Thank you everyone for the information. Some hard to understand but all appreciated.

Bob from what you're saying then (which seemed pretty straight forward) if I'm trying to get a the background separation look of f2.8 at 100mm on FF but on a dx camera I'm not going to get it with a f2.8 lens?

Not standing in the same position with the same framing and perspective, no.

I would like to swap the 5d mkiii currently using the 24-105 f4 to for something lighter and with a shallower dof (more similar to 70-200mm). My idea of D300s and an old Tokina 50-135 f2.8 probably isn't going to hit the mark background sedation wise. Sounds like it will be more like the 24-105 but obviously with more reach.

Depth of field, as you see it in the final image, is entirely determined by what's going on in front of the lens - the angle of view, subject distance and the aperture diameter. Whatever the sensor size, to get the same DOF at the same AOV you need the same aperture diameter, so there are precious little size gains to be had.

Except one - If you want shallow DOF without the size and weight, the obvious way to go is primes. f/1.8 on APS-C will give you on APS-C what you're getting on the 5DIII at f/2.8. So, an 85 f/1.8 is pretty much there (rather long) and not necessarily that large or expensive.

If you're looking at the Tokina 50-135, the Sigma 50-150 (non VR) is likely a better bet. As rare as hen's teeth, though. The D300s, BTW, is enormous. Spend a bit more, you'll actually find that the D750 is smaller, and with the aforementioned primes, could get you where you want to go. Or, the 6D (original or MkII) is also usefully smaller than the 5D III, and takes your present lenses.

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Ride easy, William.
Bob

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