F4 IS vs F2.8 non IS in low light

[Matt L]

Odd question, but would a lens that is F4 IS give the same performance in low light as the F2.8 non IS lens would?

Looking at either upgrading my sigma 17-70 2.8-4 (or4.5) i cant remember now, to either the canon 24-105 F4L IS or to to the 24-70 2.8 as the reach of the 105 would be prefered but im unsure how it would perform compared to 2.8 in low light.

Also how much is the sigma worth do you think? as i havent seen many for sale lately.

Cheers
Matt

 

[gad-westy]

The IS one should be able to take sharp images at lower shutter speeds however if you need to freeze action, faster glass is always going to be better.

 

[arad85]

F4 will focus slower in low light, IS won't freeze motion. If you're shooting static objects in low light, the IS is worth it's weight in gold. Have you thought of looking at the cheaper (bvuyt just as good quality) 17-55 IS or 15-85 IS. On a cropper, it'll give you wider at the bottom end and just as good image quality (I love the 15-85 we have on the 7D).

 

[Matt L]

F4 will focus slower in low light, IS won't freeze motion. If you're shooting static objects in low light, the IS is worth it's weight in gold. Have you thought of looking at the cheaper (bvuyt just as good quality) 17-55 IS or 15-85 IS. On a cropper, it'll give you wider at the bottom end and just as good image quality (I love the 15-85 we have on the 7D).

15-85 sounds good, didnt even realise they did that lens, I dont fancy 17-55 as i never felt the kit lens was long enough.

edit - 15-85 is 5.6 at the top end so that will be slower than the f4 i imagine.

as for the use - it wont be fast movements if there are any but there may be the odd slight movements in the subject.

 

[arad85]

15-85 sounds good, didnt even realise they did that lens, I dont fancy 17-55 as i never felt the kit lens was long enough.

edit - 15-85 is 5.6 at the top end so that will be slower than the f4 i imagine.

Yes, it is slower, but the IS system is supposedly very effective and close to 4 stops. You can see it compared (in good light) to the other Canon lenses here: http://www.the-digital-picture.com/Reviews/Canon-EF-S-15-85mm-f-3.5-5.6-IS-USM-Lens-Comparisons.aspx and as a standalone review: http://www.the-digital-picture.com/Reviews/Canon-EF-S-15-85mm-f-3.5-5.6-IS-USM-Lens-Review.aspx

All down to how low light and how much movement you have to take into account....

 

[WinstonSmith]

Manufacturer claims on IS performance are generally accepted to be highly optimistic.

 

[Skyline On Fire]

Manufacturer claims on IS performance are generally accepted to be highly optimistic.

I can second that.

Not to mention, IS is useless if there is anything moving in your shot in low light, it can stabilize it all it wants, it cant freeze the action.

Faster glass over IS every time for me.

 

[arad85]

Manufacturer claims on IS performance are generally accepted to be highly optimistic.

This is what the review on The Digital Picture says:

Camera motion blur is a great way to erase otherwise great image quality. Welcome Image Stabilization. The rule of thumb I use for determining the longest shutter speed I use to handhold a lens is 1/(focal length x FOVCF). Thus, I typically need a shutter speed of 1/(15 x 1.6) = 1/24 which is close enough to call 1/25. Specific testing with this lens at 15mm revealed that I indeed needed 1/25 for a good keeper rate with IS switched off. No surprise there. I bettered my rule of thumb slightly at 85mm with a good IS-off rate at 1/80.

Turn on IS on and my acceptable keeper rate shutter speed slows all the way down to .8 and 1/5 sec at 15mm and 85mm respectively. That is 4 1/3 stops of improvement at 15mm and 4 stops at 85mm. Canon's 4-stop rating proves out for me.

Perhaps he's talking BS, but I've seen other reports across the web (when I was researching buying) that are similar for this lens.

Not to mention, IS is useless if there is anything moving in your shot in low light, it can stabilize it all it wants, it cant freeze the action.

Faster glass over IS every time for me.

I said that in my first post 99% of the stuff I take is static, so IS wins over aperture every time for me

The correct answer is it depends on what the OP wants to shoot....

 

[odd jim]

Manufacturer claims on IS performance are generally accepted to be highly optimistic.

4 stops isnt wide from the mark with Canon's new IS systems, particuarly the ones in the 15-85 and 18-135. It really is that good.

 

[squishy]

4 stops isnt wide from the mark with Canon's new IS systems, particuarly the ones in the 15-85 and 18-135. It really is that good.

I've seen tack sharp shots from the 100L IS handheld at 1/8 sec :nuts: