Still need a fast lens?

[Dennis Ernst]

With the new 5D mark III and the high ISO speeds it will bring, do you still need or want a fast lens? Will a f/4 work just as well as a f/2.8 with a 5D mark II? Will it change the lens you might buy for it in the future?

[Leopard Lupus]

Considering what I shoot, i will keep my fast primes and continue to invest in them. Personally, regardless if a f/4 functions as well as an f/2.8, I will always still go after the 1.2s and 1.4s 

[Terry Rogers]

While an f/4 lens will probably work in more situations than before given high iso's, it won't achieve as diffuse a backround as a faster lens. If you want the most blurred backround, get a fast prime, medium blurred backround, 2.8 zoom, and lastly, moderately blurred backround (dependent on focal length) f/4 zoom. You generall save a bunch of money and weight with the slower lenses.

[pwp]

Depending on your shooting style the answer could be that f/2.8 & f/4 glass is fine. For me this is already the case with the f/4 24-105is and f/4 17-40 when hooked up to the 1D4 body in particular.

I hankered for very fast glass more back in the film days when my default film stock was 100 iso. Later it was still important with cameras like the 1Ds which got noisy after 200 iso. It was often a job saving decision to pack the 50 f/1.4 and the 24 f/1.4.

But really since the original 5D I'm happy to have f/2.8 glass in the bag from the "need for speed" viewpoint. The situation has done nothing but improve with each subsequent release. Photographers more skilled than me can deliver great results in dynamic shooting situations with f/1.2 - f/2 apertures. I need that touch more DOF to guarantee an acceptable percentage of keepers.

Paul Wright

[wickidwombat]

sometimes you just want that wide aperture bokeh and blur that only fast glass can give

[koolman]

You will find that in many cases, the faster lenses, are more expensive, and hence have better overall quality IQ and glass as they appeal to a more demanding professional audience.

True, that as ridiculously high ISO's are usable in the advanced DSLR world, the necessity of a fast lens for decent images in low light situations  - as we used to have in the film days and older digital days - is less.

Coupled with the new IS feature found in the lenses, allowing slower TV exposures, large AV's are not as important as far as exposure.

However - large AV's also have a creative affect on images as they allow much more shallow DOF - an affect you will often see in pro photography. This unique feature is not possible with slower lenses. 

[WJM]

Here are some situations when you might need high ISO speeds and a fast lens:

1. Indoor action sports. Now some sportshalls are too dark to shoot decent pictures.
2. Fast moving animals in the woods while the dusk sets in.

With the newer cameras with higher ISO speeds it is posible to shoot in these situations (while it was not possible before) but you still need fast lens (else the gain in shutter speed is gone).

[Kit.]

With the new 5D mark III and the high ISO speeds it will bring, do you still need or want a fast lens? Will a f/4 work just as well as a f/2.8 with a 5D mark II? Will it change the lens you might buy for it in the future?

Those 5 diagonal cross-type autofocus sensors on mark III will work only with f/2.8 and faster lenses. So, if you need extra AF speed, precision and reliability, f/2.8 lenses will still be better than f/4 ones.

[briansquibb]

Take the scenario of:

5D2, 1/125, iso 3200, f/2.8

The the best option from an IQ point of view is

5D3, 1/125, is3200, f/2.8

as it will give a much better picture

Rule is not to squander the technology improvements on the body just to get cheaper glass.

[00Q]

The f2.8 will give you a nice bokeh that the f4 cant achieve even if you can shoot now with a faster shutter speed on the 5DIII. So it corrects for half the problem of a slow lens, but not all.

[CR Backup Admin]

To me, it seems like there is never as much light as I'd like.  1 or 2 more stops will let me use faster shutter speeds and reduce motion blur.  I often am using my 5D MK II at ISO 6400 and f/1.4 with too slow of a shutter speed.

In good light, of course, no need for a upgrade.

[kferguson]

One thing that appears to have been mostly overlooked is the different look/feel/color intepretation and bokeh of the faster primes.  To me, there is much more of an advantage than just "speed."  Combine them with the 5D Mark III and I am hoping to really be able to unleash the beast with my primes thanks to the new focusing system.

[birdman]

Wooohhh, slow down cowboys. The 5d3 will be better in low-light, but if you are expecting a 2-3 generation jump, then you may be in for a huge surprise. One full stop in lSO raw is what I'd honestly expect.

All this does for you is make a cleaner image in low-light. Such as astrophotography, or poorly lit events. Best of luck to you all. I just cannot pull the trigger on the new 5d3 until i see reviews.

[7enderbender]

With the new 5D mark III and the high ISO speeds it will bring, do you still need or want a fast lens? Will a f/4 work just as well as a f/2.8 with a 5D mark II? Will it change the lens you might buy for it in the future?

To me that is a question that is only marginally impacted by ISO speed, IS or shutter speeds. I'll most certainly buy a few more fast primes before I'll upgrade to a 5DIII (or whatever is available by the time my Mark II breaks). I consider the very usable 3200 ISO in my current camera a bonus but I was also perfectly happy with 400 ISO film; so that's that. Same with the Mark III. Nice bonus but the new AF is actually more exciting (since there will obviously never be a full time manual DSLR ever again which would be even more exciting). So is the new flash system

Fast primes I prefer for the image quality and control over depth of field. As useful as my 24-105 is for a lot of things, but there is stuff it just can't do.

[Fandongo]

Here are some situations when you might need high ISO speeds and a fast lens:

1. Indoor action sports. Now some sportshalls are too dark to shoot decent pictures.
2. Fast moving animals in the woods while the dusk sets in.

With the newer cameras with higher ISO speeds it is posible to shoot in these situations (while it was not possible before) but you still need fast lens (else the gain in shutter speed is gone).

Damn right, I'd also like to add

3.  Wandering around at twilight, picking up incredibly clean pics/video using street lights.

The possibilities are endless with a fast lens + 5diii, go where no man has gone before (and stop down in those places).
That being said, the kit lens would be great for daytime/most photography needs, particularly if you're just beginning.

The 50 1.8 is a great place to start (you can shove it in your pocket, juggle it, etc.)
...and a 24 1.4 is a great place to end.