Ideal Amateur Birding Setup - D500/500PF vs new combo: A9/200-600

Started 3 months ago | Discussions thread
Entropius Veteran Member • Posts: 4,354
Re: Ideal Amateur Birding Setup - D500/500PF vs new combo: A9/200-600

Bill Ferris wrote:

Entropius wrote:

I have the D500 and 500PF.

It's astoundingly good.

The D500 and A9 are roughly equal in pixel count, so it's reasonable to look at equivalent focal lengths and apertures.

The D500/500PF will get you 750mm at f/8.4 equivalent and 1050mm at f/12 equivalent (using a 1.4x TC), both quite sharp.

For exposure, the D500 with a 500 PF (or 200-500), wide open, is f/5.6. Full stop. There is no equivalence conversion for exposure.

The above-quoted text may be in reference to a depth of field equivalence. For wildlife and bird photography, that factor is often irrelevant. The quality of the background is more influenced by the photographer than the gear. A good photographer is selective about backgrounds. If the D500/500 PF combo is at f/5.6 and the A9/200-600 combo is at f/6.3 with good photographers shooting both, I would not expect to see any significant depth of field advantage or penalty in the images coming off either system.

The math also holds for the equivalent amount of light gathered (which determines the signal to noise ratio in everything but the deep blacks). On modern sensors the quantum efficiency is about the same, so the noise level is almost completely determined by the total number of photons gathered, which is proportional to the total aperture area. I wasn't thinking about dof (which as you point out isn't that big of a deal), but about signal to noise ratio (which matters a great deal for action/low light).

Another way to look at this is the following: for instance a 500mm on DX will capture the same image area as a 750mm on FX. If both lenses were f5.6, both cameras will be set to the same ISO, which means that both sensors will be receiving the same amount of light per unit area. But the FX sensor has greater area, and what determines signal to noise ratio is the (inverse square root of the) total number of photons collected. (This is just a fancy mathematical way of saying that FX sensors are less noisy at any given ISO.)

But a 750 f/8.4 on FX gathers the same amount of light as a 500 f/5.6 on DX, and thus gives the same signal to noise ratio at a given shutter speed. It will do so at a higher ISO (since the sensor is getting less light per area).

 Entropius's gear list:Entropius's gear list
Nikon D500 Sigma 18-35mm F1.8 DC HSM Art Nikkor AF-S 300mm f/4E PF ED VR
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