TS-E 17 mm for landscapes/nature

[peter_e]

<p>I appreciate all your effort and expert opinions presented here! Very informative. Jeff, good observation on the retrofocus/tilt issue. I usually do not attempt to eliminate convergence of verticals completely, so it has not bothered me on the 45 mm. All this means, of course, that I need another excuse now for further procrastinating on ordering a $ 2200 lens... Well, I'm sure it is very heavy!</p>

[scott_ferris]

<p>No it's not! The convergence is very easy to eliminate too. No excuses! Don't tell anybody but I got my absolutely totally mint one, in box still wrapped in the original plastic bags, from a very well rated seller, off eBay for $1,725. A real bargain, but they are out there.</p>

<p>Take care, Scott.</p>

[jeff_conrad]

<p>Peter, when I first noticed the convergence when playing with the tilt on my 24, I thought I was losing it. I had just made a diagram proving that lens tilt doesn't change magnification. There was one small problem with the diagram ... I'd used the typical Gaussian thin-lens approximation, and my geometrical inferences relied on coincidence of the pupils and nodal planes; though the approximation works for most lens-tilt derivations, it doesn't work here. When I re-drew the diagram with the pupils separated from the nodal planes, my “proof” no longer worked. I never did get around to proving that magnification did change, so to be honest, I was partially guessing at the cause until I chanced upon <a href="http://www.largeformatphotography.info/forum/showpost.php?p=316132&postcount=31">this post</a> by Emmanuel Bigler (a professor of optics) in the <a href="http://www.largeformatphotography.info/forum/index.php">Large Format Forum</a>, which confirmed what I had suspected.</p>

[dan_south]

<blockquote>

<p>The short wall, top left, is vertical and the armchair is square.</p>

</blockquote>

<p>The distortion of the armchair is a wide-angle lens effect. The near side of the chair appears to be larger than the far side. The tilting wall I cannot explain. I haven't seen a problem like this when the camera has been carefully leveled.</p>

[scott_ferris]

<p>Dan,<br>

The right hand side of the chair is "leaning" in, I meant the side of the chair is square. This is a known optical effect of retrofocus lenses, the shorter the focal length, the more pronounced. I'll do another shot latter if you like, but I can assure you the bubble level was perfectly lined up. It is an effect that is very easy to deal with though, as Jeff said, all you need to do is put a little "rear" tilt (the camera) to counteract it.</p>

<p>As Jeff hypothesised, the extreme difference between the focal length of the 17mm, and the comparatively massive percentage of retrofocus, make the effect with 17 particularly pronounced.</p>

[scott_ferris]

<p>Here is a graphic example of short focal length retrofocus T/S lens convergence when tilt is used.<br /> Neither the camera or tripod were moved throughout the first three shots, only the tilt was adjusted. This is the run down of images</p>

<ol>

<li>Control shot, leveled and plumb with the two pillars.</li>

<li>Full 6º down tilt.</li>

<li>Full 6º up tilt.</li>

<li>Full 6º down tilt with camera tilted back to zero convergence.</li>

<li>Camera set up for shot 4 showing back tilt of camera (with pillar in background for reference).</li>

</ol>

<p>Hope this helps, Scott.</p><div></div>

[jeff_conrad]

<p>You get similar effects with any asymmetrical lens. It's quite pronounced on the original TS-E 24, less pronounced but noticeable on the TS-E 45 (which is a retrofocus because the tilt/shift mechanism puts the glass so far away from the image plane), and barely noticeable on the TS-E 90 (which is slightly telephoto but close to symmetrical).</p>

<p>It sometimes takes a couple of tries to fix the convergence if you absolutely must have vertical lines perfectly vertical in the image. But these are extreme examples: maximum tilt, and obviously vertical features near the vertical image edges. In more typical cases, a slight convergence often isn't even noticeable. If possible, try to anticipate the convergence before precisely setting the tilt; if you tilt the camera back after setting the tilt, you'll need to reset the tilt to get the PoF where you want it.</p>

<p>Peter, the second image also addresses one of your questions. The beam at the top is clearly out of focus. If you shoot a lot of landscapes with a frame such as this, you might have a problem; if not, it's an unpersuasive excuse ...</p>

[dan_south]

<p>Scott, you have effectively illustrated the phenomenon. My question would be why you would ever need six degrees of tilt except in an extreme macro setting (or for special effects). I rarely use more than one degree of tilt with my TS-E24 II. That's plenty to get everything on a horizontal surface in focus unless the camera is very low to the ground.</p>

<p><img src="http://www.dansouthphoto.com/Places/New-York-Downtown-Wall-Street/NY-Downtown2010-09-2011/1028254333_tMqGJ-L.jpg" alt="" width="800" height="534" /></p>

<p>One degree of tilt at f/8. The camera was less than three feet above the wood surface. Vertical lines are unaffected.</p>

[scott_ferris]

<p>Dan,</p>

<p>I completely agree, I would hate to cast aspersions on the 17mm TS-E and have people think it has a fault. I even posted a more extreme example than yours, the one where the camera is very close to the deck, it had 2º of tilt and no convergence. In real world use I can't foresee an issue, it was just an observation of an optical side effect.</p>

<p>I am very very happy with my lens, as an added "advantage", with one shift and perfect auto stitch alignment, I have ended up with a 40mp medium format sized sensor.</p>

[dan_south]

<p>I'm glad to hear that you like the TS-E 17 so much, Scott. Maybe I'll ask the Easter Bunny to bring me one next spring. ;-)</p>

 

[scott_ferris]

<p>If your bunny can carry it, Dan, then do ask. It is the lens I have been looking for.</p>

<p>I do have one bit of advice/comment I'd give to the Canon team for a possible MkII version in ten years or so. You are quite right, 6º of tilt seems a lot to be effectively usable on this focal length (so far), it has too much dof for counter tilt "toy" images, and closeups, where it might be really useful, can put the subject dangerously close to the front element. I do have one job where I might use it all though, a guitar, <a href="http://shutterbug.com/equipmentreviews/accessories/0104sb_cambos/">similar to this image</a>, I'll know in a few weeks as I have a guitar shoot. What I would like to see though, is much finer gearing over fewer degrees, it only takes a short throw of the knob to tilt the full range, spread that out over a couple of rotations and it would be far nicer.</p>

<p>Take care and I'll keep my fingers crossed for a good Easter for you :-). Scott.</p>

<p> </p>

[peter_e]

<p>Scott: The lack of finer control for tilt is also my only complaint with the 45 and 90 mm. Obviously, less ciritical there than for 17 mm.</p>