The problem of manual focus with very fast lenses is real and can be a major pain. Some DSLRs with interchangeable focus screens have a special screen for fast lenses. That would be a great idea for wedding photographers, for example, probably one of the primary groups who use very fast lenses like the Canon 50mm f/1.2 and 85mm f/1.2.

What is “very fast” also depends upon the focal length. Short focal length lenses can be “faster” than longer lenses because of size limitations–not to mention cost! The fastest long telephoto for Canon cameras today is the Canon 200mm f/2L IS. It weighs 5.6 lb and costs $5,300. (In contrast, the 35mm f/2 lens weighs 0.46 lb and costs $300.) Go beyond 200mm and the fastest lens for Canon DSLRs is f/2.8 (300mm & 400mm), then f/4 (500mm & 600mm), then f/5.6 (800mm). Even with “slower” apertures, supertelephoto lenses are huge and incredibly expensive.

300mm f/2.8L IS: 6 lb, $4,100
400mm f/2.8L IS: 11.7 lb, $6,800 (the favorite lens for many sports photographers)
500mm f/4L IS: 8.53 lb, $5,300 (probably the #1 favorite lens for pro bird & wildlife photographers)
600mm f/4L IS: 11.8 lb, $7,600
800mm f/5.6L IS: 9.9 lb, $10,999

One has to wonder if the 400mm & 600mm lenses come with their own forklifts. They make my “behemoth” zooms–70-200mm f/2.8L IS @ 3.5 lb with collar, 3.2 lb without and 100-400mm f/4.5-5.6L IS @ 3 lb–seem dinky. Those zooms are at about the upper limit for handholding, even with IS. Anything heavier should be used on a tripod or monopod. Pointing my 100-400mm up to try to catch birds in flight (e.g., soaring hawks) shows me that I need to hit the gym! Even worse would be the Sigma 50-500mm f/4-6.3 at 4.1 lbs (no wonder it’s called “Bigma”), which doesn’t have image stabilization.

Many of the fast lenses used in portrait work, are manual or set to manual focus. Automatic focusing lens are nice and seemingly easy to use but think about what really is going on. You might find the camera focusing on another portion of the subject. The end result could be that your camera chose another main subject and that may not be your initial intentions.

For example, the Pentax SMC-A, 50mm f/1.2 that I used on my Pentax K20D. It’s not the easiest to use properly at the “faster end”. Should you desire allot of boken, (shallow depth of field), to bring out a subject, that also means you will need to be very exact when you focus. That can be difficult for many people, especially for the older foke out there with aging eyesight! (I’m included in that bunch! LoL)

One example is a photo of my mother.

In this picture, notice how shallow the depth of field really. This was a quickly taken shot that I thought was properly focused. Many portrait photos will have the eyes in focus, my original intention. The end result here was great looking teeth and nose but not the eyes. I’m lucky this was not a paying customer but if it was, I would have had more time to properly set things up. It’s not often I get to take her photo so I’ll have to live it.

Remember the difficulty focusing before running out to purchase a really fast lens for big bucks. Leave that to the advanced amatures and professional.

17-40mm f/4 L [$700]
24-105mm f/4 L IS (the “kit” lens for the 5D, for example) [$1059]
70-200mm f/4 L (IS and non-IS) [$1100 & $600]
(The 70-200mm f/4 L IS has been called the “best zoom lens, anywhere” by several reviewers, including some who mostly use Nikon equipment.)

Canon has two other L zooms, with wider ranges and non-constant maximum apertures, but these are harldy “fast” lenses.

28-300mm f/3.5-5.6 L IS [$2300]
100-400mm f/4.5-5.6 L IS [$1460]

The other “fast” lenses (f/2.8 or larger) by Canon are all primes:

14mm f/2.8 L II [$2020]
15mm f/2.8 Fisheye [$610]
20mm f/2.8 [$445]

24mm f/1.4 L [$1170]
24mm f/1.4 L II [$1699]
24mm f/2.8 [$305]

28mm f/1.8 [$420]
28mm f/2.8 [$180]

35mm f/1.4 L [$1180]
35mm f/2 [$240]

50mm f/1.2 L [$1400]
50mm f/1.4 [$325]
50mm f/1.8 [$90]
50mm f/2.5 Macro [$250]

85mm f/1.2 L [$1870]
85mm f/1.8 [$355]

100mm f/2 [$410]
100mm f/2.8 Macro [$470]

135mm f/2 L [$935]
135mm f/2.8 Soft Focus (actually quite sharp!) [$295]

200mm f/2 L IS [$5300 !]
200mm f/2.8 L [$695]

300mm f/2.8 L IS [$4100]

400mm f/2.8 L IS [$6500]

(N.B.: At 300mm +, many would consider f/4 lenses to be “fast.”)

Let’s make some comparisons to show the penalties for “ultra-fast” lenses. The first number is the price at B&H, the second is the weight, the third is the filter size, which translates into cost, as well:

50mm f/1.2 L $1400 19.2 oz 72mm
50mm f/1.4 $325 10.2 oz 58mm
50mm f/1.8 $90 4.6 oz 52mm

F/1.2 and f/1.8 are a little bit more than 1 stop apart. That stop will really cost you: 15+ times the price, 4+ times the weight, plus more expensive filters.

The 50mm comparison is probably the “worst,” but other one-stop differences are also instructive. (I didn’t compare IS or Macro lenses to non-IS):

35mm f/1.4 L $1180 20.5 oz 72mm
35mm f/2 $240 7.4 oz 52mm

85mm f/1.2 L II $1870 36.8 oz 72mm
85mm f/1.8 $355 14.9 oz 58mm

70-200mm f/2.8 L $1190 45 oz 77mm
70-200mm f/4 L $600 25 oz 67mm

and the real shocker:

300mm f/2.8 L IS $4100 5.6 lb rear filter
300mm f/4 L IS $1059 2.6 lb 77mm

So, if you want really fast lenses, be prepared for a major hit on your wallet and sore arms, to boot.

For wedding & event coverage I find myself in some dim interiors so I pack up the Nikon glass in these arrangements:

f/1.4 – 50mm
f/1.8 – 85mm
f/2.8 – 10.5mm,17-55mm, 70-200mm

1.8 does a good job of bluring out the background, while letting an extensive ammount of light in, so you can shoot at a faster shutter speed, and acheive the same level of brightness, etc, as you would on a 3.5 or 5.6 F. Plus its sharper too because theres less blur, and less grain.
-Hope that helps someone out there.

-Eric

28mm f/1.8 (45mm equivalent, or ‘normal’ view)
50mm f/1.8 (80mm equivalent, or ‘portrait’ view)
85mm f/1.8 (136mm equivalent, also useful for portrait work)

These are all useful for available light work, and of course, for those situations where you want a shallow depth of field, but I also find them useful for flash work, as well.

Consider that you gain an effective 2-3 stops of flash range over the more typical zoom lenses. This equates to stretching your flash range out quite a bit, as well as helping to avoid that ‘dark cave’ look where the background brightness falls off sharply. Coupled with the Canon DSLR’s ability to take practically noise-free shots at ISO 400, 800, or even 1600 with some of the latest bodies, you have a really flexible setup for natural light or flash situations.

Try shooting in Manual mode, or at least Av (Aperture preferred) and experiment with the camera and flash settings to see how you can balance the background room light with the lighted foreground subject.

When you want to understand exactly how the Canon EOS flash system interacts with your flash and camera settings, check out:

http://photonotes.org/articles/eos-flash/