APSC F2.8 vs FF F4

I'm currently very much in doubt which camera I should get (a 7DII or Nikon D750). APS-C vs FF. I have shot with both systems for a couple years but never side by side. I'm looking for good lowlight performance and fast AF in all situations.

Both cameras I can afford with some nice primes, but when it comes to zooms, I could buy the 7D2 with the 17-55/F2.8 and still spend less then buying a FF with a F4 zoom.

Now I wonder if I would lose IQ when going for APS-C compared to the FF. Anyone can comment on this. I know DOF will be a tad less on the APS-C but I wonder when you compare F2.8 on APSC to F4 on FF if the difference would be noticeable. I tend to use (need) high ISOs too though, mainly to keep the shutter speed high. When using a F2.8 zoom, I suppose that's easier on APS-C then compared to a FF when using a F4 lens.

Thanks for your input.

Having studied this myself before purchasing the 70D, I found that the IQ differences become acute under high iso circumstances, otherwise the differences may only be apparent when pixel peeping. If you want it all, e.g. low light performance and fast autofocusing, you're looking for the 1Dx. From there, it's all about compromise. What is more important?

iowajim wrote in post #17211859
Having studied this myself before purchasing the 70D, I found that the IQ differences become acute under high iso circumstances, otherwise the differences may only be apparent when pixel peeping. If you want it all, e.g. low light performance and fast autofocusing, you're looking for the 1Dx. From there, it's all about compromise. What is more important?

i don't get this place. one of the OP's primary concerns is money and you mention a 1Dx???

OP, i'll say this. one big thing to consider with FF is the glass, unless you use primes, you dont get to buy the cheaper EF-S mount glass. FF zooms are expensive. so you need to consider if the lens you intend to get will serve you long enough.

high ISO performance is night an day with FF over aps-c and the DOF control is much better too.

mike_311 wrote in post #17211867
i don't get this place. one of the OP's primary concerns is money and you mention a 1Dx???

What's not to get? The point that he either needs to go 1Dx or compromise is valid.

If high iso is the highest concern, FF is the way to go. If focusing is more important, look to the 7Dii.

Focussing is important not for action shots (although sometimes I do), but mainly to keep track of kids running, playing, not sitting still and also for quick AF response indoors when there's not enough light. My a6000 for example is pretty good outdoors, but when indoors with tungsten lights, it starts to struggle.

"High ISO, low light"... For some 1600 is high and regular room lights are low.

I was thinking to get 30 1.4 for my 500D to have it more compact comparing to 5D with 50L. But at the same time it was thread here were 24-105L on FF was compared with something faster on crop. I couldn't find this thread after, it was impressive.

Kids and such, higher shutter speed... I would just get 5D MKII with Tamron zoom.

I don't see much difference between FF and crop in IQ if files or in prints, but here is something different in FF photos. It is like more air and light in them.

f4 lenses are getting popluar on a FF bodies becuase the high ISO ability is that good. f4 on a newer FF at say 3200 or even 6400 will give you cleaner images than f2.8 on an APS-C at 1600 and definitely 3200.

I wouldn't pass up FF for any body except the 7d2, and thats assuming that autofocus and burst is that much more important than high ISO and IQ.

lapino wrote in post #17212369
Focussing is important not for action shots (although sometimes I do), but mainly to keep track of kids running, playing, not sitting still and also for quick AF response indoors when there's not enough light. My a6000 for example is pretty good outdoors, but when indoors with tungsten lights, it starts to struggle.

The 6D has excellent low light focusing ability, and is the high iso champion for the moment. You might investigate this further with 6D owners.

lapino wrote in post #17211605
I'm currently very much in doubt which camera I should get (a 7DII or Nikon D750). APS-C vs FF. I have shot with both systems for a couple years but never side by side. I'm looking for good lowlight performance and fast AF in all situations.

Both cameras I can afford with some nice primes, but when it comes to zooms, I could buy the 7D2 with the 17-55/F2.8 and still spend less then buying a FF with a F4 zoom.

Now I wonder if I would lose IQ when going for APS-C compared to the FF. Anyone can comment on this. I know DOF will be a tad less on the APS-C but I wonder when you compare F2.8 on APSC to F4 on FF if the difference would be noticeable. I tend to use (need) high ISOs too though, mainly to keep the shutter speed high. When using a F2.8 zoom, I suppose that's easier on APS-C then compared to a FF when using a F4 lens.

Thanks for your input.

IF you frame with both cameras using the FL appropriate for the format to obtain the same AOV, the APS-C (e.g. at 31mm) has MORE DOF than FF (e.g. at 50mm) at the same aperture, not less as you stated!

Because the 14.9 x 22.5mm image of APS-C has to be magnified by 1.6x greater than the 24 x 36mm frame of FF to make the same FINAL PRINT, the lens' OPTICAL RESOLUTION is always taxed to a greater degree by the smaller format.

As someone who shot medium and large format film cameras professionally, putting my 135 format gear to rest only until I wanted something suitably compact and lightweight for vacations, I can say that most of the time I shoot APS-C and rarely ever say "I wish I had my FF camera with me instead!" for personal leisure use. So the quest for 'more IQ' does go overboard for a lot of folks. If you NEVER make a print larger than 13" x 19", you likely will never appreciate any IQ advantage of the larger FF camera, apart from the fact that larger pixels capture more photons and result in lower noise images than APS-C.