APS-C Lens on Sony A7S

A

Armando Ferreira

Member
I have a Sony A7S and really love the Sigma 18-35mm F1.8. I know it's for APS-C cameras but why shouldn't I use it for my A7S? The A7S has an APS-C mode so it will only use that part of the sensor, I also understand the focal length is going to change to aprox 28-55mm (which I'm ok with). Are there any drawbacks? I haven't seen any picture degradation or loss in quality when in APS-C mode. Phillip Bloom also confirmed this in his review. I mainly shoot video in 4K and was curious if anyone would give me a good reason not to go that route.
 
Armando. The a7S can go into "APS-C" mode. Go into your menus and scroll over to the second folder tab, the one with the Cog icon. Go to sub-menu 5 in that menu and fifth item down is APS-C Size Capture mode. Turn that on.

A couple of benefits of APS-C mode is your are effectively shooting in Super35, so if you are use to lens size calculations with Super35 it will help you out. Also there is less rolling shutter that is visible.

The camera is probably quite new to you. Good idea to spend some time just going through the menu system to ingrain where things are and discover what features the camera has.
 
i think the uhd in aps-c mode is upscaled from 2.7k as its not using the full sensor, so not quite as sharp as full frame
 
Andrew, it looks like he understands that camera can do apsc, he's just wondering if there are any drawbacks.
Armando, ade4all is correct. If you shoot 4k in apsc you're actually upresing a 2.7k image. So you will suffer some degradation compared to full frame.
 
Andrew Stone said:
Armando. The a7S can go into "APS-C" mode. Go into your menus and scroll over to the second folder tab, the one with the Cog icon. Go to sub-menu 5 in that menu and fifth item down is APS-C Size Capture mode. Turn that on.

A couple of benefits of APS-C mode is your are effectively shooting in Super35, so if you are use to lens size calculations with Super35 it will help you out. Also there is less rolling shutter that is visible.

The camera is probably quite new to you. Good idea to spend some time just going through the menu system to ingrain where things are and discover what features the camera has.
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LOL I've owned this camera since the day it came out, I'm fully aware that the A7S has an APS-C Size capture mode (I stated that in my initial post). I'm more concerned if there are any drawbacks. I'm OK with the change in focal length, I just always hear people say "only use FF lenses".
 
caseywilsondp said:
Andrew, it looks like he understands that camera can do apsc, he's just wondering if there are any drawbacks.
Armando, ade4all is correct. If you shoot 4k in apsc you're actually upresing a 2.7k image. So you will suffer some degradation compared to full frame.
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Thanks, what I wanted to hear. If I do recall, Phillip Bloom in his review said that he was impressed that you couldn't tell a loss in quality in APS-C mode. I've also seen other reviews say the same thing, how certain are you that it's up scaling to 4K? The GH4 is a micro four thirds and uses APS-C lenses but also shoots 4K. Does that mean the GH4 is also upresing?
 
there is no reason why apsc mode would be worse in 1080p. in 4k its a different story since the apsc part of the sensor just isnt 4k.
 
HeldvomFeld said:
there is no reason why apsc mode would be worse in 1080p. in 4k its a different story since the apsc part of the sensor just isnt 4k.
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I'll give it a try with my current setup. I'll shoot some stuff in FF and then APS-C and see if I can tell a difference. I'll try and match (compose) the shots as close as possible so it looks like it was from the same focal length. I'll upload video on YouTube and you guys can tell me if you can notice a difference.
 
Armando Ferreira said:
Thanks, what I wanted to hear. If I do recall, Phillip Bloom in his review said that he was impressed that you couldn't tell a loss in quality in APS-C mode. I've also seen other reviews say the same thing, how certain are you that it's up scaling to 4K? The GH4 is a micro four thirds and uses APS-C lenses but also shoots 4K. Does that mean the GH4 is also upresing?
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I have not watched his review, but I can only imagine the image might be a bit more "filmic" in it's softer quality. The gh4 isn't upscaled because it's sensor is smaller to begin with, so all the pixels are being used (apsc is larger than mft so it covers the sensor without issue) when it's shooting 4k. The a7s has only just enough pixels really to get 4k in 16:9, so when you effectively cut out nearly 1/3 of the sensor, you're only left with 2.7k worth of pixels.
 
Armando Ferreira said:
I'll give it a try with my current setup. I'll shoot some stuff in FF and then APS-C and see if I can tell a difference. I'll try and match (compose) the shots as close as possible so it looks like it was from the same focal length. I'll upload video on YouTube and you guys can tell me if you can notice a difference.
Click to expand...
lol... Yt.... Difference? Mush vs mush? Everything looks the same on yt...
 
caseywilsondp said:
I have not watched his review, but I can only imagine the image might be a bit more "filmic" in it's softer quality. The gh4 isn't upscaled because it's sensor is smaller to begin with, so all the pixels are being used (apsc is larger than mft so it covers the sensor without issue) when it's shooting 4k. The a7s has only just enough pixels really to get 4k in 16:9, so when you effectively cut out nearly 1/3 of the sensor, you're only left with 2.7k worth of pixels.
Click to expand...

Makes sense, funny you say more "filmic" because when I've shot in APS-C mode I do see that softer look and I like it.
 
caseywilsondp said:
Andrew, it looks like he understands that camera can do apsc, he's just wondering if there are any drawbacks.
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Apologies Armando. I had just woken up from a short sleep after doing a long editing session. Should know better than to do that. Didn't read your post thoroughly enough.
 
I quite often pop between APSC and Full Frame modes on shoots to say changes lenses (in 1080p) and I've never seen a difference in quality in the edit.
would like to try that Sigma myself actually, surprised I hadn't thought of it.
 
APS-C Cons:
2.6K upscaled to UHD instead of true UHD if using a HDMI recorder.

APS-C Pros:
Less rolling shutter
Less moire and aliasing at 50/60P since it doesn't line skip like FF does.

Other than that the quality is practically the same.
 
In 1080p, the FF mode keeps full image quality up to 30p, then it starts doing line-skipping. APS-C keeps full image quality up to 60p.
In 4K, FF is probably sharper all the way, since APS-C is an upscale from 2.7K and FF is a pixel-per-pixel straight debayer.
In both modes, APS-C has less rolling shutter, and more noise (in terms of noise, switching to APS-C is equivalent to increasing the ISO by one stop; I use up to 12600 in FF mode and only up to 6400 in APS-C mode).
 
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