F2.8 and light with Canon 17-55 and Sigma 18-35

Can anyone who has used both of these lenses tell me which one lets in more light at F2.8?

Out of curiosity, why is this important to you?  It should be exactly the same, and if it isn't, the difference would be extremely small.  It just seems like a very odd question.

J A C S wrote:

My guess would be the Sigma because it would vignette less at f/2.8. I do not think that the difference would be small.

yep, I think you're right.  At 17-18mm the T-stop difference might be 1/3 stop at center to about 1 stop at the corners.  Not so much at 35mm.

http://www.the-digital-picture.com/Reviews/Lens-Vignetting-Test-Results.aspx?Lens=398&Camera=452&FLI=0&API=0&LensComp=854&CameraComp=736&FLIComp=0&APIComp=2

Strange question but hard to answers:

• If you have Sigma 18-35, then just shoot it at f/1.8.  Isn't that the whole point of buying it in the 1st place?  Why bother with f/2.8 is you own this lens????

• While Canon 17-55/2.8 may be 1 1/3 stop slower to Sigma, it also makes up for it by having a 3 Stop Image Stabilization.  allowing you to shoot at slower shutter-speed (1/10s ~ 1/40s) while retain sharpness.

In my experience, image stabilization worth its weight in gold.  It allow you to take sharp photo even at flow 1/10s ~ 1/30s and remove minor handshakes.  While fast prime w/o IS will give me more shutter-speed, higher shutter-speed isn't always practical.  For example, shooting at 1/60s~1/100s in lowlight often result in pitch-black-backdrop.  Where as using slower 1/10S ~ 1/40s allow me to illuminate the backdrop and avoid the pitch-black backdrop that I find annoying.

J A C S wrote:

007peter wrote:

For example, shooting at 1/60s~1/100s in lowlight often result in pitch-black-backdrop. Where as using slower 1/10S ~ 1/40s allow me to illuminate the backdrop and avoid the pitch-black backdrop that I find annoying.

The flash freezes the main subject and the background is blurred anyway - so 1/10 to 1/40 sec without IS on this shot would not have made much of a difference.

You're right that both lens will take the SAME PHOTO setting them both at 1/10s ~ 1/40s shutter-speed, in theory.

But in real life, you're dealing with arm fatigue, hand tremors, etc...Keep in mind that Sigma 18-35mm /1.8 is a bulky heavy lens @ 811g, which makes it front heavy & balance poorly on smaller/lighter weight DSLR.  It is easy to shoot @1/10s without IS on smaller prime like 50/1.4.  It another when trying to shoot @1/10s without IS on a large fix f/1.8 zoom like Sigma 18-35.

I hate Pitch-Black-Backdrop, so whatever lens I used (c17-55 or s18-35) I need to keep the shutter-speed between 1/10s ~ 1/40s.  For me, Image Stabilization becomes real handy in this scenario ensuring I get good keeper rates without a tripod.

Great Bustard wrote:

007peter wrote:

J A C S wrote:

007peter wrote:

For example, shooting at 1/60s~1/100s in lowlight often result in pitch-black-backdrop. Where as using slower 1/10S ~ 1/40s allow me to illuminate the backdrop and avoid the pitch-black backdrop that I find annoying.

The flash freezes the main subject and the background is blurred anyway - so 1/10 to 1/40 sec without IS on this shot would not have made much of a difference.

You're right that both lens will take the SAME PHOTO setting them both at 1/10s ~ 1/40s shutter-speed, in theory.

But in real life, you're dealing with arm fatigue, hand tremors, etc...Keep in mind that Sigma 18-35mm /1.8 is a bulky heavy lens @ 811g, which makes it front heavy & balance poorly on smaller/lighter weight DSLR. It is easy to shoot @1/10s without IS on smaller prime like 50/1.4. It another when trying to shoot @1/10s without IS on a large fix f/1.8 zoom like Sigma 18-35.

Your rebuttal is that an 811g lens is so heavy that it's going to make you shaky? Well, alrighty, then! May I recommend the 18-55 IS STM over the 17-55 / 2.8 IS for you. At 205g, it's much lighter than the 811g 18-35 / 1.8 and the 645g 17-55 / 2.8 IS, not to mention a lot less expensive.

Read the title, my reply is clearly state to @JAC at the title.  I wasn't talking to you.  Why do you insist on butting in?

i have my opinion to OP thread, you disagree that is fine, you're entitle to your opinion.  But that last reply was specifically address to another person.  Are you so bored with your life that you feel the need to squeeze into other's conversation?

It clearly you're looking to START a flame war of some kind.  Sorry, but some people here do have a life to attend to.  I don't hang out here 24/7, Joe.

rweaver85 wrote:

Can anyone who has used both of these lenses tell me which one lets in more light at F2.8?

Sounds like you are asking about measured T stop and that can all be looked up on DXO's website.  I believe the Sigma 18-35 has a actual T stop closer to the f stop the lens displays than the 17-55.   if memory serves me right the 17-55 has a t stop score of 3.4 so it's almost 2/3rd of a stop slower than the 18-35 at f2.8.

007peter wrote:

Sorry, but some people here do have a life to attend to. I don't hang out here 24/7, Joe

This made me chuckle coming from a person with nearly 10,000 posts. A little quick math puts you at like 85 posts a day averaging like 3.5 posts every hour of the day since joining the forum in 2006 almost 10 years ago.

Great Bustard wrote:

jitteringjr wrote:

007peter wrote:

Sorry, but some people here do have a life to attend to. I don't hang out here 24/7, Joe

This made me chuckle coming from a person with nearly 10,000 posts. A little quick math puts you at like 85 posts a day averaging like 3.5 posts every hour of the day since joining the forum in 2006 almost 10 years ago.

Heh! That said, I do spend way too much time here. More and more of it in the Off Topic Forum -- it's like picking a scab.

If you add up my posts on other forums, both photog and non photog, I'm not much different either.

One thing to consider is that the Sigma is sharp at f1.8, whereas tha Canon is not sharp until about f3.5. I have the Canon 17-55 and while a good alrounder, I find the wide open performance the main drawback.

I am considering moving to the Sigma, as I'm shooting photos of kids and they move, so IS is of less value, but the ability to shoot 2 stops faster shutter speed is of more benefit. Just wish that the Sigma had a longer focal length .... but we all need to make compromises

jitteringjr wrote:

007peter wrote:

Sorry, but some people here do have a life to attend to. I don't hang out here 24/7, Joe

This made me chuckle coming from a person with nearly 10,000 posts. A little quick math puts you at like 85 posts a day averaging like 3.5 posts every hour of the day since joining the forum in 2006 almost 10 years ago.

Today (2015-08-21) is 3461 days since 2006-02-28.

9907 messages / 3461 days = 2.86 messages / day.

You are off by a factor of 30.

- H

jitteringjr wrote:

rweaver85 wrote:

Can anyone who has used both of these lenses tell me which one lets in more light at F2.8?

Sounds like you are asking about measured T stop and that can all be looked up on DXO's website. I believe the Sigma 18-35 has a actual T stop closer to the f stop the lens displays than the 17-55. if memory serves me right the 17-55 has a t stop score of 3.4 so it's almost 2/3rd of a stop slower than the 18-35 at f2.8.

That's what I was looking for.  Thanks!