I last blogged about this in 2008, and unfortunately much hasn’t changed since then. We’ve seen quite a few new DSLR’s released, both professional and amateur, and as I suspected, Both Nikon and Canon (and others) have not yet been able to spread out the AF points in their full-frame DSLR bodies. We have yet to see the Canon 5D mk3, but I’m betting that at most it will have Canon’s new 21 point AF module found in the 7D, which will be the same physical size and therefore SMALLER in the full-frame viewfinder compared to the crop-frame viewfinder. Allow me to demonstrate what Canon’s 1.6x and 1.0x viewfinders look like, with the diamond arrangement AF points in their advanced-amateur & semi-pro camera bodies:

What you are seeing is an outline of how far the focus points spread out in the viewfinder. The Canon 40D / 50D / 7D focus point spread is the larger diamond, and the Canon 5D / 5D mk2 is the smaller diamond.

It’s a similar situation with the Canon 1.0x and 1.3x flagship bodies:

And, it is a similar situation with Nikon’s 1.5x and 1.0x bodies:

Then, just to get REALLY provocative, here’s some fightin’ words: The 5-series Canons versus the 300 series Nikons-

(I just recently twittered a potentially offensive statement- the fact that I notice quite a large majority of images made with 5-series Canons have their subjects placed dead-center. I see this with practically every photographer who owns a 5-series Canon, so don’t think I’m singling YOU out…)

The bottom line (the point I want to make) is that, unfortunately, full-frame sensors are NOT perfection. Despite their huge advantages in low light and familiar angle of view with full-frame lenses, they do have a disadvantage or two. Focus point spread is one of the key issues.

Each time a new full-frame camera comes out, I hope with all my might that either Nikon OR Canon will spread out their AF points, but they haven’t yet. In my blog entry back in 2008, I pondered a few reasons why that might be:

It is a technical limitation caused by the angle at which light hits a full-frame sensor. On full-frame at wider angles, light hits the sensor at quite an angle sometimes, and I guess this kills the autofocus accuracy. The crop-sensor lenses however usually receive light at a better (perpendicular) angle, so they can AF correctly even at the apparent edge of the frame, since it’s not nearly the edge of the true full frame…

This and a few other laws of physics / optics (whatever) are certainly the culprits, otherwise they’d be putting AF sensors right to the very corners of our viewfinders.

…Now, the last bit of discussion is the tough one, the one that nobody wants to talk about. The reason that Chenin Boutwell switched to Nikon recently and now sings the praise of the Nikon D700. Let’s buckle up and open this can of worms!

Basically, on ALL cameras the center AF point is the most powerful, the most accurate, and the one you should always use if you CAN. Of course that’s quite limiting, creatively. Fortunately, there are something called “cross-type focus points”. (I explain this all at my exposure, metering and autofocus workshop) …Your center AF point is always cross-type, and depending on which camera you have there are other cross-type AF points around the viewfinder for you to use and they are quite accurate.

Canon’s 1-series bodies are the best in this respect, the outer rim of AF points is EXTREMELY accurate. Canon’s pro-series AF system has two concentric circles of cross-type AF points, and on the 1.3x crop you can pretty much focus on ANY subject and almost perfectly follow the rule of thirds. (Scroll up and have a look at the diagram)

Nikon’s 51 point AF system is also great, but their cross-type AF points are clumped in the center in three columns of five AF points. That central area is incredibly accurate, and Nikon wins in some tests for low-light accuracy and tracking with the D3 / D3s AF. However, the off-center focus points to the left and right are not cross-type, and are slightly less accurate. Since they’re so close together you can group nine points together to “aide” in focusing, which really works well if your subject isn’t sprinting towards you.

Canon’s advanced amateur 1.6x crop bodies, the 40D and 50D, have all nine cross-type AF points in a diamond pattern. All 21 AF points on the 7D are cross-type, too. Again remember that the center AF point is always the most accurate, but an off-center focus point that is cross-type is your next best bet and if you use good AF technique you can get at least 50% or more of your shots perfectly in focus.

However, last (and possibly least) comes the 5-series Canons. Quite frankly the equivalent of a Sputnik in today’s high-tech world of autofocus. Its design is literally based on the 20D and 30D from 2004 and 2006, with a few extra “secret” AF points added around the center point to help out in low light.

Thus the can of worms discussion. Is a 5-series good enough for a professional to use and trust? Apparently so, because hundreds of thousands of professionals around the world used both the 5D and the 5D mk2 with amazing results. A tougher but still obvious question: Is it *optimal*? Decidedly not. I’ve shot professionally with both the 5D mk1 and mk2, and I can honestly say that using the D300 and D700, my standards have simply been spoiled. I could make do with a 5-series, but I wouldn’t want to. So what do you do about it?

Well first of all, in all honesty the off-center points on the 5D mk2 aren’t that bad if you know how to use them. I’ve used the mk2 many times, and with the proper technique you can get many perfectly focused shots. It just takes a little bit more attention to technique than other cameras might. Which is a good thing; it keeps your skills sharp. There’s nothing worse than having a camera so good that you get sloppy and start cutting corners technically.

Or, you can focus + re-compose. Use the center AF point to focus, and then re-compose before you shoot. This requires a thorough understanding of the different AF modes on your camera and maybe the decision to use the rear AF-ON button. (Wonderful tool for shooting action, by the way. If you ever bump into me and want to know how it works, I’d be happy to show you. Or you can wait for another exposure / metering / autofocus workshop.

Focus + re-compose has it’s limitations, however, and is nearly impossible to do if a subject is moving. Or if you like shallow depth and often find yourself shooting at f/1.4 or f/1.2, you can pretty much count on only ever getting 1-2 shots in focus for every 5-10 that you click. (If you’re shooting standing up at close distances. Again, this is best discussed visually in person…)

Therefore, LOTS of 5-series images end up getting composed with a dead-center subject. This looks cool once every now and then when you’re going for the “rules are meant to be broken” thing. But at the end of the day it’s still a creative limit.

There is HOPE for the future though. All signs point to a forthcoming 5D mk3, and it should AT LEAST have Canon’s new 7D AF module. Even though it will still cover approximately the same area as previous 5-series bodies, it’ll be a dramatic improvement. Or maybe Canon could go all the way and make a semi-pro body that has the 45-point AF system for under $3K. But now we’re definitely getting into wishful thinking territory

While we’re thinking wishfully, HOPEFULLY Canon or Nikon will spread out their AF points on full-frame bodies in general. Whoever does it first doesn’t matter to me, Canon or Nikon, because if one sets the bar then the other will have to rise to that bar sooner or later.

Lastly, I wish Nikon would at least re-arrange their cross-type AF points. This would be awesome; I don’t know if anyone has ever used the D2H or D2X but WOW those off-center cross-type AF points are snappy. Almost as good as the Canon off-center cross-type AF points…

Sadly I don’t know if this will ever happen. We’ll probably be stuck with the current AF point spread and configuration for at least another generation or two. Partly to blame is this whole HD video craze, which is certainly the #1 R&D priority right now. I understand how “fusion” is going to change our industry, and I appreciate the amazing new low-light video capabilities, but I’m sad to think that other matters, more true to traditional photography, are going to take a back burner for a while.

…So, all this to say- such a dramatic difference between crop and full-frame cameras is one of the main reasons I continue to shoot with my Nikon D300. And I will continue to shoot with it even after I eventually add a full-frame D700 to my bag. Unless I need that extra bit of low-light performance, the D300 suits me perfectly.

DISCLAIMER: If you own a 5-series Canon, don’t think I’m insulting your camera OR your work. I’m just a camera geek who loves a good discussion of pros and cons. And if you shoot with a 5-series but DO manage to shoot lots of off-center compositions, and/or get a high number of perfectly focused shots, many kudos to you! I never said it was impossible, I’m just discussing the degree of difficulty.

Take care,
=Matt=