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Author Topic: tilt shift or f22?  (Read 4250 times)

Ben Rubinstein

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tilt shift or f22?
« on: August 09, 2006, 07:06:28 pm »

As I understand it there is only one plane of focus. This is the point where the focus is sharpest, the only true point of focus in an image. Stopping down, using hyperfocal focusing, using a wider lens only serves to reduce the 'unsharpness' of the rest of the image which is 'in focus'. Those areas are not sharply focused like the point of focus, instead they are less out of focus than other areas.

I shoot a lot of landscape work with longer lenses, I like the compression, I see in telephoto and only rarely in wide angle. As such I'm stopping down to f16-f22 to maximise DOF. However at that stage I'm running into diffraction with f16 at the limit of what is 'ideal' with my 70-200L lens on a FF sensor. Of course as MR wrote in an article some years ago, getting the photo is more important than being too anal about diffraction but for those of us not in the big money and trying to maximise all the potential of our cameras.

Primes are one answer, they are sharper but the inherent problem is still there.

With that in mind should we not be aspiring to using tilt shift lenses so that we can to some extent (35mm T/S lenses don't move that much do they?) fix the problem right from the start by extending DOF with movements to ensure that the ultimate point of focus, that plane, is extended over much of our scene or all of it, enabling us to use the optimum fstop for sharpness and killing 2 birds with one stone?

At this point I should admit that I've never used large format or a T/S lens and do not have but the smallest understanding of the concepts involved. Just seems to me that I would be getting a sharper front to back image with a 90mm t/s at an optimum f8 or whatever, than a prime 85mm at f16-22.

Am I at all right? For landscape work is movements a far better solution than super sharp and expensive lenses stopped all the way down?
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Ray

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tilt shift or f22?
« Reply #1 on: August 09, 2006, 08:07:39 pm »

Speaking purely from my own experience here with my own 2 T&S lenses, the 90mm and 24mm, the problem in using tilt for landscapes is the difficulty of moving the components in the landscape, such as trees or any tall object, to fit the new tilted focal plane. Consequently there is a danger of getting parts of the image, which might normally be reasonably in focus, suddenly out of focus in a surprising and unintended way. Furthermore, the small viewfinder of the 35mm format doesn't help. It's not always clear what parts might unintentionally be OoF, so there can be quite a bit of stuffing around involved.

The problem is worse with the TS-E 90mm because of the longer focal length. In a sense, there's a Catch 22 situation here. Using tilt with the TS-E 90mm is of greater benefit, if you can get it right, because DoF is shallower and there is more to lose by stopping down to f16 and f22 because this is a sharp lens. Using tilt with the TS-E 24mm is easier but mostly not necessary because such a wide angle lens has great DoF in any case. I would have no hesitation in using f16 with the TS-E 24mm if getting maximum DoF was an issue since this is not a particularly sharp lens. In fact, now that I'm using a 5D, I should probably be using f22 in circumstances where I used to use f16 with my D60 and 20D.

That might be my next lens test, comparing TS-E 24mm sharpness at apertures from f8 to f22   .
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pfigen

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tilt shift or f22?
« Reply #2 on: August 10, 2006, 01:38:44 pm »

Pom,

I own all three Canon T/S lenses plus a bevy of Schneider view camera lenses. I disagree with the previous poster about the difficulty using Canon's 90 T/S. You just have to control the plane of focus to optimize your overall focus objectives. I actually find the 90 the easiest of the three to focus, priimarily due to its shallower viewing depth of field (90mm f/2.8). By comparison, the 24 and 45 can be almost impossible to accurately focus, at least through the viewfinder. Shooting tethered and viewing immediately afterward on screen if the best way to check focus. There are some good books about view camera technique that will apply equally well to the Canon. Once you understand basic Scheimpflug effect, it will all seem very simple. Here's one of many hits that came up on Google. BTW, the 90 works incredibly well with the Canon EX1.4 extender, giving you a 127mm T/S. There appears to be little or no loss of detail. Haven't tested it with a 2X though.

http://www.trenholm.org/hmmerk/VuCamTxt.pdf
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Jack Flesher

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tilt shift or f22?
« Reply #3 on: August 10, 2006, 04:27:50 pm »

The simple answer is yes, using tilt can alter the PoF (Plane of Focus) to the point it gets two disparate points of interest in an image together in that plane and thus both in focus at the same time.

The more complex answer is what Ray alluded to in his response -- that you can only alter that PoF along *one* axis with the TSE lenses and get two significant points of interest in focus in the image, but other significant points may be moved far outside that new PoF...

Enter the view camera -- the big advantage is you have tilt (horizontal) adjustments and swing (vertical) adjustments together and can thus define the PoF in almost any direction.  This however only allows a third point of interest to be added in with the other two and thus other points in the image may be well outside this new PoF as well.  

The upsides are 1) in a landscape image there is usually a distinct foreground and background and a little tilt usually is sufficient to make the image right; 2) that an image requiring more than three significant points of focus is probably going to be too busy anyway   However, for those images where we want the infinite DoF look all over the image we may have no other choice than to to use a wider lens and move closer, or just make the best compromise we can with the PoF.

This 'problem' is the very reason I have gone back to using a view camera for my more serious landscape work.

Cheers,
« Last Edit: August 10, 2006, 04:30:28 pm by Jack Flesher »
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Ray

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tilt shift or f22?
« Reply #4 on: August 11, 2006, 10:07:15 pm »

Quote
I disagree with the previous poster about the difficulty using Canon's 90 T/S. You just have to control the plane of focus to optimize your overall focus objectives. I actually find the 90 the easiest of the three to focus, priimarily due to its shallower viewing depth of field (90mm f/2.8). [a href=\"index.php?act=findpost&pid=72980\"][{POST_SNAPBACK}][/a]

pfigen,
Would you care to post some example images of typical landscape shots (as opposed to macro shots or product shots of positioned articles on a table) where you've achieved an f32 DoF at, say, f8 with the TS-E 90mm?
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Gary Ferguson

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tilt shift or f22?
« Reply #5 on: August 12, 2006, 06:22:54 am »

Quote
Am I at all right? For landscape work is movements a far better solution than super sharp and expensive lenses stopped all the way down?
[a href=\"index.php?act=findpost&pid=72906\"][{POST_SNAPBACK}][/a]

Pom, yes you are right, movements are better, but (and it's a huge but!) this is only normally true if the landscape you are photographing doesn't have tall objects in the foreground. So if for example your scene has a tree or a horse or a rock in the foreground that's taller than about one third of the frame height, then movements won't allow you to get the entire scene in focus at wide apertures.

I've written an article on alternative focusing techniques for Luminous Landscape that reviews some of the software based routes to extended depth of field as well as looking at an intriguing and surprisingly effective technique based around small apertures and infinity focus. I'm not sure when Michael intends publishing it but it gives some practical examples.
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Peter Jon White

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tilt shift or f22?
« Reply #6 on: August 15, 2006, 08:19:13 pm »

I've been using the 35mm Tilt/Shift Canon since the mid eighties on the F-1. I now have another one which has been converted to EF mount, and the three TS-E lenses. I also use a 4x5 Wisner with lots more movement than any T/S lens on a small format body.

On the F-1, the 35 is quite easy to use. The F-1's focusing screens are better than anything available for the 5D. I can easily see what's in focus and what's not. So using tilt to get the maximum amount of subject into sharp focus in a landscape shot is very effective.

On the 5D it's not quite as easy, but it's pretty close. Certainly with the 45mm and the 90mm you can easily see the plane of sharp focus moving about as you make adjustments. With the remounted 35 on the 5D I have to work a bit slower than with the F-1 due to the lower viewfinder magnification and brightness, even with the Ee-s screen. But I can get just as good results, it just takes a few more minutes.

With the 24 TS-E it's considerably slower going than with any of the other lenses, partly due to the shorter focal length, and partly due to the smaller maximum aperture. I can't use the Ee-s screen due to the small aperture (it will be very dark) and the grid screen is helpful anyway. But you don't get the enhanced sense of DOF you get with the Ee-s screen. So be prepared to spend a good deal longer setting up a shot with the 24.

Of course, as I've noted previously here, there's no reason to limit yourself to shooting landscapes with short lenses now that we have longer lenses available that tilt. The 45 and 90 TS-E lenses make some very interesting images possible that before their introduction would simply have been impossible to make with a small format camera.
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