Sigma 18-35 Brightness Change on Zoom

[W.D. Stevens]

Hi all,

I've had my Sigma 18-35 since January and loving it so far. I did notice that, when zoomed in (around 24mm+, I think), it actually gets brighter. I initially figured that it was because of the adapter I was using but I've since bought a Metabones BMPCC Speedbooster and it's the same. Not really an issue for me as I very very rarely zoom within a shot but I wanted to know whether it was a defect or a quirk (a defect we like).

[stevesherrick]

Hi all,

I've had my Sigma 18-35 since January and loving it so far. I did notice that, when zoomed in (around 24mm+, I think), it actually gets brighter. I initially figured that it was because of the adapter I was using but I've since bought a Metabones BMPCC Speedbooster and it's the same. Not really an issue for me as I very very rarely zoom within a shot but I wanted to know whether it was a defect or a quirk (a defect we like).

Happens to mine too.

[Denny Smith]

Most still camera zoom lenses, even if they have a set f/stop, are not totally consistent with the light transmitted, and will have small variances in actual,light transmission. Shooting stills, most DSLR cameras adjusts for this and you do not see an exposure shift. Kim is working on a remote zoom/Iris controller that compensates for the Iris shift on some zoom lenses.

Cine zooms solve this issue, and is why they are so much more expensive.
Cheers

[W.D. Stevens]

Huh, well, I never knew that. The things you learn, eh? As I said, not really an issue for me as I don't do a lot of zooming within a shot and even if I did, this is probably not the lens for that. Thanks, all!

[Denny Smith]

Yes, I always yhink'of a good still camera zoom like the Sigma as a "variable" focal length lens, you dial,in the focal length you want, then shoot.
Cheers

[_OZ]

The effect seems, subjectively, to also be exacerbated with lens adapters, since there is a longer cavernous path for the light to travel until hitting the sensor.

[Karguil]

This defect seems good but not at all times. I agree that it's not the lens but finding what could be the factors that causes it could help you identify the issue and solve it if you must.

[Taikonaut]

I find zoom lenses including Sigma 18-35 less bright and have lower contrast than most primes.

Canon pancake primes are also similarly less bright and low contrast just like zoom lenses.

The brightest lenses I uses are all Zeiss primes.

[AaronChicago]

I find zoom lenses including Sigma 18-35 less bright and have lower contrast than most primes.

Canon pancake primes are also similarly less bright and low contrast just like zoom lenses.

The brightest lenses I uses are all Zeiss primes.

Really? I feel like my Sigma 18-35 is higher contrast than any of my primes (Nikkor, Xeen, Rokinon).

[jimagine]

Agreed. Contrast and sharpness are both signature qualities of the 18-35mm.