F4 vs F1.8

NnZ · Oct 15, 2015

Hello guys. I have the SeL1670z mounted on the a6000. I have no experience using a Fast Prime and planning to purchase the 24mm 1.8 or 35mm 1.8

Main question is how much difference would the performance be in low light? Is it really that big of a difference going from f4 to f1.8?

TIA

nandbytes · Oct 16, 2015

That's more than 2stops, so yes its a pretty big difference.

If you want to simulate the exposure in live view, set your camera on a tripod in a dark room and take you shutter speed down by 2 stops. Eg: 1/120->1/60->1/30.

Of course f/1.8 will have a shallower DoF compared to f/4.

pb21 · Oct 16, 2015

Don't forget that the 24 mm f 1.8 doesn't have OSS which allows for around 3 stops and would negate any gain going from f 4 with OSS to f 1.8 without.

rlyons · Oct 16, 2015

pb21 said:
Don't forget that the 24 mm f 1.8 doesn't have OSS which allows for around 3 stops and would negate any gain going from f 4 with OSS to f 1.8 without.

OSS will help for static subjects but f/1.8 will give you faster shutter speeds than f/4 will. So if a faster shutter speed is required the f/1.8 is your friend.

So, I wouldn't say that it's negated by OSS. It really depends on what type of low light shooting you do and whether a faster shutter is more important.

Entropy512 · Oct 16, 2015

rlyons said:
rlyons said:

Don't forget that the 24 mm f 1.8 doesn't have OSS which allows for around 3 stops and would negate any gain going from f 4 with OSS to f 1.8 without.

Click to expand...

OSS will help for static subjects but f/1.8 will give you faster shutter speeds than f/4 will. So if a faster shutter speed is required the f/1.8 is your friend.

So, I wouldn't say that it's negated by OSS. It really depends on what type of low light shooting you do and whether a faster shutter is more important.

For example, in concert photography, OSS will let you get a musician's body to be fairly sharp but if they've got a guitar their hands will be blurry.

blue_skies · Oct 16, 2015

NnZ said:
Hello guys. I have the SeL1670z mounted on the a6000. I have no experience using a Fast Prime and planning to purchase the 24mm 1.8 or 35mm 1.8

Main question is how much difference would the performance be in low light? Is it really that big of a difference going from f4 to f1.8?

TIA

ISO 800 versus ISO 3,200? Yes, huge difference.

Or, 1/60th versus 1/15th? Yes, huge difference.

Jerry R · Oct 16, 2015

OSS allows the use of slower shutter speeds but f/1.8 allows 4x as much light to reach the sensor as f/4.

NnZ · Oct 16, 2015

Thanks all for your input.

Follow up question, I am pretty sure if this has been asked before but is the IQ of the 24f1.8z be really that much better from the 35f18? I am also contemplating as I also checked and no OSS for the 24f18z.

The 24f18 can be purchased here for $950 VS $500 for the 35f18.

Thanks again in advance guys. Really appreciate the inputs.

Docrum · Oct 16, 2015

Yes, it's a massive difference in the real world.

The SEL35F18 has OSS, the SEL24F18 doesn't. There is a substantial difference in the field of view between the two. Check out the difference using your 16-70 and see what will suit you best.

NnZ · Oct 17, 2015

Docrum said:
Yes, it's a massive difference in the real world.

The SEL35F18 has OSS, the SEL24F18 doesn't. There is a substantial difference in the field of view between the two. Check out the difference using your 16-70 and see what will suit you best.

Thanks for the input Docrum

. Do you have any idea about the Image Quality difference between the two?

davect01 · Oct 17, 2015

F1.8 can allow for some great low light shots, but gives you such a narrow Aperture that it can be difficult to get exactly the right focus. A steady hand and/or tripod is often needed.

T3 · Oct 17, 2015

NnZ said:
Hello guys. I have the SeL1670z mounted on the a6000. I have no experience using a Fast Prime and planning to purchase the 24mm 1.8 or 35mm 1.8

Main question is how much difference would the performance be in low light? Is it really that big of a difference going from f4 to f1.8?

TIA

It's a big difference. I think even f/2.8 is slow for low light. There's also a big difference in DOF and background blur control.

Docrum · Oct 17, 2015

NnZ said:
Docrum said:

Yes, it's a massive difference in the real world.

The SEL35F18 has OSS, the SEL24F18 doesn't. There is a substantial difference in the field of view between the two. Check out the difference using your 16-70 and see what will suit you best.

Click to expand...

Thanks for the input Docrum . Do you have any idea about the Image Quality difference between the two?

Sorry that was in response to your original question re f4 vs f1.8 . I don't own the SEL35F18, but I do have the SEL50F18 and SEL24F18Z. For me, the SEL35F18 wasn't a wide enough field of view, however the OSS aspect would have been nice.

I've got some shots on Flickr using the SEL24F18Z in low light https://www.flickr.com/photos/132399567@N06/albums/72157655227616404 . The sort of situations where f4 wouldn't have worked well (without additional lighting or a tripod.)

Edit: I just found a couple of relevant groups on Flickr:

SEL35F18 - https://www.flickr.com/groups/2121072@N20/ and https://www.flickr.com/groups/2208115@N22/

SEL24F18Z - https://www.flickr.com/groups/1753425@N23/ and https://www.flickr.com/groups/1917998@N22/

tammons · Oct 18, 2015

F2 = iso 800

is 2 stops from...

F4 = iso 3200

Charles Lynn · Oct 19, 2015

There is difference, but not so huge, normally speaking, most people don't need shoot in such dark places. Even you need do it occasionally, just boost ISO would be suffice. On A6000, you can safely boost ISO to 6400, even higher if you don't need print in huge size.

If you want shallow depth of the field, just use 70mm end and adjust the distance between your subject and background , you would be OK.

And you make want to save the money to wait for the a6000 II, which ISO performance maybe remarkable.

dquangt · Oct 19, 2015

NnZ said:
Thanks all for your input.

Follow up question, I am pretty sure if this has been asked before but is the IQ of the 24f1.8z be really that much better from the 35f18? I am also contemplating as I also checked and no OSS for the 24f18z.

The 24f18 can be purchased here for $950 VS $500 for the 35f18.

Thanks again in advance guys. Really appreciate the inputs.

yes the 24mm is better. however, the bigger difference is the focal length. i have both lenses so my advice is to take the 1670 and set it to each focal length and go around for a bit and see which one you like more. the 24mm is way more useful for me.

tammons · Oct 19, 2015

To me the larger difference is if you have to stop down say 2 stops to get sharp corners.

With an F4 lens now you are down to F8.

With a F1.4 lens 2 stops is at F2.8 so big difference.

Charles Lynn · Oct 19, 2015

For the SEL16-70mm, you don't need to stop down 2 stops to get sharper photos. It's always sharp.

Charles Lynn · Oct 19, 2015

By the way, now days most lenses are sharp enough, almost nobody can tell the differences between them. I never know even one person who can just look at a photo, then tell me which camera or lens the photographer use to take it. It's just impossible.

Paul_B Midlands UK · Oct 19, 2015

Use a F1.8, you might not want to use an F4 ever again. A lot of opportunities open up with superfast lens that suck in light. They are a bit addictive.

F4 vs F1.8

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