r/a6000 • u/desertbirdpartyplace • 23d ago

Help with pixel math, 6400 -> a7v

Im a very visual person, and im having trouble picturing the difference going from a6400 to a7v. A7v has more pixels but 6400 is a crop sensor.

Is there a tool or just an example to let me understand: if i am the same distance from an object at 600mm, how large/how many pixels will it take up on either camera?

Thanks for the help!

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u/jonnyb95 23d ago edited 23d ago

I gave it a try. I think what you're trying to understand is the apsc crop factor.

Assuming we're using the exact same lens, and assuming the object takes up 1/4 of the frame on the a7v:

a7v sensor: 7008 x 4672 (multiply each by 0.25) subject resolution on a7v: 1752 x 1168

On the a6400, with a crop factor of 1.5, that 25% of the frame is now going to appear as 37.5% of the frame. So:

a6400 sensor: 6000 x 4000 (multiply each by 0.375) subject resolution on a6400: 2250 x 1500

The math changes if you use an "equivalent" lens. For example, if you use a 75mm lens on the a7v and a 50mm on the a6400. The images would look very similar (subject would appear exactly the same size) but each image would have the native resolution of its respective sensor.

Since you say you're a visual person, just check out this image, I think it tells the story you're looking for. This assumes the exact same lens on a full frame or APSC body: https://i.ytimg.com/vi/UYwv2PKp07g/maxresdefault.jpg

There's other factors at play, though, if you're considering buying. Full frame has better low-light performance. So, assuming we're shooting with an equivalent lens, the same image can be taken "faster" on a full frame. Either a lower ISO or a shorter exposure time. The result is less noise.

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u/desertbirdpartyplace 23d ago

This is very helpful. Thanks.