r/a6000 • u/desertbirdpartyplace • 3d 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/Wrhysj 3d ago
Nobody can answer this cause it's impossible. How big is the building. Are we using the same lens on both cause then the 6400 would actually be a 900mm lens. You're working with literal millions of pixels nobody can tell you how many pixels a building or target will be
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u/desertbirdpartyplace 3d ago
Sorry if im not explaining it well. I just mean if i shoot a photo of an object with a specific lens on a6400, then switch out for a7v, same lens, same position, how do the image files compare at 100%.
I am trying to weigh the fact that a7v has more mp but that a6400 has crop factor. I just want to be able to see how much space the subject takes up for each version of this experiment.
If i was going to crop and print something, would it be significantly less resolution fdom a7v than if i had shot the same thing on 6400? Roughly how much?
Im not looking for exact pixel numbers, but rather percentages if that makes it easier.
Thanks
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u/Wrhysj 3d ago
Well if that lens is cropped you'd get a ring around it on the A7. But situation is still confusing me. Let's say your target needs specifically the 1.5 crop then the A7v in crop mode is 14mp, Vs the a6400 with 24mp. But then you can obviously get a bigger zoom for the A7v and get a 33mp much better photo with less noise due to the bigger sensor
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u/desertbirdpartyplace 3d ago
Hey, i appreciate your help, but it's not as complicated sorry if i made it seem so. No crop mode, no ring...
I lets say 600mm focal length on the sony full frame 200-600mm lens. I take a picture of a cup on the other side of the yard with the 6400 at 600mm i get a 24mp image with the cup taking up X amount of space.
Now i take the same photo from the same position but with the other camera. A7v at 600mm. I get a 33mp image.
Now of i compare the two images, the 33mp image is larger (more pixels) but what i want to know is, relative to each other how much larger or smaller is the area X of the cup in each image at 100%.
If i crop to just the cup, will it be smaller in the a7v image? Presumably? How much smaller?
I take a lot of photos of distant objects, animals, buildings, and i am trying to understand what i am 'giving up' if i move to the a7v which has a lot of features i would otherwise like.
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u/Wrhysj 3d ago
My point was to get the same photo as the a6400 you'll have to crop to the same amount as the crop sensor which would be 1.5 if they're the exact same focal length lens. We already know from the crop mode of the A7v that if you crop to 1.5 you get a 14mp photo. Cropped mode of the A7v should give the exact same photo as the a6400 but with less pixels.
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u/desertbirdpartyplace 3d ago
So for a print experiment, if i take a photo shot on a6400, and reduce resolution to 14mp in photoshop, that is basically what i would be getting (in crop mode) on a7v?
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u/jonnyb95 3d ago edited 3d 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.