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Tip of the Month

Canon 17mm T/S lens

August 2011

fern stream
Canon 17mm TS Lens, 4 seconds at f/22. ISO 100.
This stream scene was shot at Tall Timbers, in Bald Eagle
State Forest, during our D-CNPC field trip


This is not an endorsement. Far from it.

Canon is introducing several new lenses, and one of these is the 17mm T/S lens. These Tilt/Shift lenses incorporate the Scheimpflug principle which, in effect, lays the plane of focus, or the depth of field down or up and not necessarily parallel to a camera's film or sensor plane. Normally, depth of field increases or broadens by gaining some degree of focus in front of and behind a point of focus, both being parallel to the film plane. If you can imagine this depth being tilted, effectively pointing forward, so that the plane now extends at an angle, the depth of field, or area of focus would or could extend further. I often refer to this as laying down the depth of field, kind of like laying a carpet down on a floor to extend outward, rather than hanging that same carpet and having the carpet hanging vertically. GOOGLE Scheimpflug and you can read several accounts on this principle, and good luck with it. Better to see it, or have it explained in words you may be able to understand!

This Scheimpflug principle, however, provides one great advantage with T/S lenses since one can enjoy great depth of field at larger apertures, and thus faster shutter speeds, rather than requiring small apertures and slower shutter speeds. In fields of flowers, for example, one might with a T/S lens have the same depth of field at f8 at 1/250th as one would have with a traditional lens at f22 at 1/30th. If there is a breeze, 1/30th would not be fast enough to stop any motion, but 1/250th might.

I own a 24mm T/S and a 90mm T/S lens, and recently I borrowed the new 17mm T/S lens by Canon. For nature photographers, I couldn't understand the attraction, and perhaps Canon has introduced the lens for the Shift feature as much as for the Tilt, and has designed the lens for architectural photographers. I don't know. At any rate, a traditional 17mm lens has incredible depth of field, so the lens seemed irrelevant.

I have an App on my Ipod called DOFMaster where I can dial in data and get the depth of field for a particular lens at a given f-stop and focusing distance, as well as the Hyperfocal Distance. It is a great App, and illustrates why, to me, this lens isn't a must-have for nature photographers.

Here's some numbers:

At f/11, at a focusing distance of 2 feet, the total depth is 5.4 feet, with the DOF near limit at 1.18 feet, and the far limit 6.58 feet. The Hyperfocal Distance at f11 is 2.85 feet, meaning (for the multitude who really do not understand what Hyperfocal Distance means) that the DOF would be 1.42 feet to infinity.

At f/22, the DOF is infinite, with the near limit .84 feet and the far limit infinity, with the Hyperfocal Distance 1.45 feet. That's 10 inches to infinity.

I didn't try measuring or determining DOF with the 17mm T/S lens for either aperture, and I suspect that the DOF might reach infinity at f11 when my lens is focused at 2 feet. Perhaps I could use an even wider aperture, giving me a still faster shutter speed that would help freeze any action with the T/S lens, and still reach infinity. I do not know of any DOF charts that would provide this data, since the Tilt of these lenses is variable.

T/S lenses should provide greater DOF than traditional lenses if the Tilt feature is used correctly, so in practical terms you should be able to get a faster shutter speed, to freeze action, and still have great DOF with wider apertures. The Shift feature might come in handy for panoramas, since the Shift literally shifts the field of view from left to right, which the rotation of a pan head on a tripod will accomplish as well.

I didn't find the lens convenient to use in the field. I had to be low to get close to the fern (as I would have had to be with a traditional 17mm). I was using f/22, so my shutter speed was slow (four seconds), requiring me to use Mirror Lockup and an electronic cable release. This, the expensive intervalometer version, dangled into the stream and short-circuited, but fortunately worked properly once I took out the battery and drained the system. I think I was lucky.

I own the Canon 16-35mm wide-angle lens, and although I might have to use slower shutter speeds than would be required with the T/S lens, for as often as I'd use it I think I can live with this limitation. The 17mm T/S lens is big and heavy, with a huge protruding front element, and I was constantly nervous in the field that I might scratch the front element of a lens I borrowed from a good friend.

So, what is the Tip? I'd seriously question whether this lens has much application or need by a nature photographer. It is heavy, T/S lenses are a bit cumbersome to use, and at 17mm you have great DOF, although slower shutter speeds might be required. If you shoot cities, or product, perhaps it is the best lens ever invented, but for nature, think twice, unless you have a big backpack and a big wallet.



Previous Tips, July 2009 onward


Locking Button for the Canon 7D
NIK HDR Program

Silver Efex Pro for Black and White Images

Beware the DELL Software Solution Rip Off
How and What We Pack for Trips

Canon Digital Learning Center

The Movie Mode with the Canon Mark IV
Batch Renaming in Bridge and CS5
Alternate Uses of some Bogen Products

Hoodman Products

Using High ISO and Live View for Focusing in Dim Light

Art Print Scams for Hungry Photographers

Hungry Vultures ruin vehicles in the Everglades

Use a Short Lens for Depth of Field

Get Professional Help!

Mini-Molar Bag
Access America Trip Insurance
Bogen Base for Macro Work

Archived Tips of the Month
prior to July 2009
Most of my original Tips of the Month for the last several
years are available through this link. The 'look' is from my
original web site, although if I ever have enough time I might redo these pages to match the new web site But that's not a high priority.