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09-06-2010, 09:30 AM   #1
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Shift lens question

I've never used one, but know they are obviously capable of showing buildings and verticals without distortion. My question is how they work with subjects/objects close to the lens. One usually uses it for buildings a reasonable distance away, but are the verticals straight and the subjects distortion free even if they are close to the lens? Say 3-5 feet away?

Also, Pentax only has shift lenses and not tilt/shift. What are the advantages of having the tilt feature?

09-06-2010, 09:46 AM   #2
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QuoteOriginally posted by K-9 Quote
I've never used one, but know they are obviously capable of showing buildings and verticals without distortion. My question is how they work with subjects/objects close to the lens. One usually uses it for buildings a reasonable distance away, but are the verticals straight and the subjects distortion free even if they are close to the lens? Say 3-5 feet away?

Also, Pentax only has shift lenses and not tilt/shift. What are the advantages of having the tilt feature?
You can turn “off” the shift feature and use this lens as a regular 28mm wide angle. It’s not as sharp as a prime wide, but not terrible either. (Minimum focusing is 1 foot or .3 meter.)

You can “shift” this lens in the horizontal or vertical position.

Phil..
09-06-2010, 11:48 AM   #3
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Being an admirer of the great view camera photographers, I'd be very interested in trying a tilt lens on my K-7, but I didn't know Pentax made one. What's the lens to which you're referring?

Thanks

JVA
09-06-2010, 12:50 PM   #4
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QuoteOriginally posted by K-9 Quote
What are the advantages of having the tilt feature?
Tilt is used to control the orientation of the plane of focus and hence the part of an image that appears sharp.

09-06-2010, 01:14 PM   #5
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QuoteOriginally posted by jva59 Quote
Being an admirer of the great view camera photographers, I'd be very interested in trying a tilt lens on my K-7, but I didn't know Pentax made one. What's the lens to which you're referring?

Thanks

JVA
SMC Pentax K28/3.5 Shift:

http://www.pentax.ca/pdf/o_manuals/om_28MMSHIFT_e.pdf

Phil.
09-06-2010, 01:49 PM   #6
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QuoteOriginally posted by gofour3 Quote
You can “shift” this lens in the horizontal or vertical position.
You can actually shift it in any direction. It has twelve click-stops around the clock, but can be stopped between the clicks too.
Unfortunately 28mm isn't really wide enough on APC-S sensors, it's a fun lens but not very useful for perspective correction. In some rare occasions yes, but in a city/street environment you can seldom get far back enough to frame the whole building. And when you can, there's not that much need for the correction. Picture quality leaves nothing to desire, though.

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09-06-2010, 01:59 PM   #7
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QuoteOriginally posted by bilybianca Quote
You can actually shift it in any direction. It has twelve click-stops around the clock, but can be stopped between the clicks too.
Unfortunately 28mm isn't really wide enough on APC-S sensors, it's a fun lens but not very useful for perspective correction. In some rare occasions yes, but in a city/street environment you can seldom get far back enough to frame the whole building. And when you can, there's not that much need for the correction. Picture quality leaves nothing to desire, though.

Kjell
Yes the K28/3.5 Shift works best on film. I only shoot film and the 28mm FL is perfect, the built in filters are also a big asset.

I mostly use it in the vertical position.

Phil
09-07-2010, 06:29 AM   #8
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Thanks, Phil!

09-07-2010, 10:16 AM   #9
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Just to give you something to think about...

I've done view camera work in the long distant past, and I always desired a tilt/shift lens for my SLR's, but I never bought one, mostly for reasons of cost/weight/bulk (as you can tell from my signature, I'm a minimalist). Fast forward many decades to today, and I'm finding I've finally got enough robust pixels with my K-7 (my old Nikon D100 didn't cut it in this regard) that software perspective correction is now totally viable, in fact remarkably so. I use it often, and the resulting images are not degraded at all from all the pixel shuffling, at least not that I can see, and I'm pretty critical. It works so well that I no longer desire a tilt/shift lens. As for your question about closer-up subjects, I guess I haven't used software perspective correction in that way, but it would certainly work just as well.

If you are interested in my methods, I use Photoshop CS5, place a grid over the image (command + apostrophe), and use Edit>Transform>Distort to make my adjustments. The grid helps enormously.

Here's a few examples, although it's hard to tell much about image quality from these little JPEG's. These all make beautiful 13x19 prints - no one would ever guess they have been "manipulated" in such a way, they really look great.





09-07-2010, 11:42 AM   #10
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Many thanks again, Phil & for manual as well. Slinco, that's very illuminating.

Another question (as you can see, I'm beginning to covet this lens!). Apart from the principal reason to use a shift lens, namely to correct perspective, esp. when photographing architecture, such lens are also said--according to a principle bearing the name of its German discoverer, which I've forgotten--to be useful for increasing DOF. Does that square with the experience of those of you who've used the K 28 mm shift lens?
09-07-2010, 01:09 PM   #11
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With a TS/PC lens shifted down, apparent DOF increases somewhat. Scheimpflug Principle

To correct perspective distortion, it's easily done in PP, with some cost in resolution.

For cheap, you can build a 'lensbaby' type fitting for a short (25mm) enlarger lens.

Various threads discuss using a PP lens for distortionless stitched panoramas.
09-07-2010, 03:21 PM   #12
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QuoteOriginally posted by jva59 Quote
Many thanks again, Phil & for manual as well. Slinco, that's very illuminating.

Another question (as you can see, I'm beginning to covet this lens!). Apart from the principal reason to use a shift lens, namely to correct perspective, esp. when photographing architecture, such lens are also said--according to a principle bearing the name of its German discoverer, which I've forgotten--to be useful for increasing DOF. Does that square with the experience of those of you who've used the K 28 mm shift lens?

I am detecting a bit of confusion as to what happens with what. The perspective correction that everyone talks about is the normal convergence of parallel lines that shows when the film plane is not parallel to the subject plane. Here is how shift and tilt help with that issue:

Shift
Shift is really sort of hokey. Simply put, it allows you to fit the top of a tall object in the frame without tilting the camera upwards (film plane remains parallel to subject plane). This is done by projecting a large image circle and placing the image frame at a position other than center. Obviously, there are limits (based on image circle size and focal length) on how much you can accomplish with shift.

Tilt
Tilt allows you to:
  • Change the angle of the film plane relative to the subject plane (lens axis remains perpendicular to the subject plane). This allows manipulation of perspective.
  • Change the angle of the lens axis relative to the film plane (film plane remains parallel to subject plane). This allows manipulation of plane of focus (Scheimpflug principle) so that both near and far elements of the subject can be in focus even with moderate DOF.
  • Any combination of the above.
Very cool! Again, the ability to manipulate perspective or the plane of focus using tilt is limited by the projected image circle of the lens and the amount of tilt supported by the T/S lens.

Regarding Lens Options
  • Very few support fully independent tilt and shift in all directions
  • Shift only lenses are more common than T/S
  • They are expensive
  • The amount of perspective control is small compared to that provided by a view camera


So, in summary...
Shift is nice and very useful. Tilt adds a ton more flexibility. Even at best, a T/S lens is easily outdone by a camera designed with built-in movements.


Steve

Last edited by stevebrot; 09-07-2010 at 03:40 PM.
09-07-2010, 07:26 PM   #13
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Many thanks, Steve, that was v. much to the point and illuminating to this reader.
09-08-2010, 12:02 AM   #14
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QuoteOriginally posted by RioRico Quote
With a TS/PC lens shifted down, apparent DOF increases somewhat. Scheimpflug Principle

To correct perspective distortion, it's easily done in PP, with some cost in resolution.

For cheap, you can build a 'lensbaby' type fitting for a short (25mm) enlarger lens.

Various threads discuss using a PP lens for distortionless stitched panoramas.
The idea of combining shift/tilt lenses with stitching sounds interesting!!!
09-08-2010, 10:57 AM   #15
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QuoteOriginally posted by JoepLX3 Quote
The idea of combining shift/tilt lenses with stitching sounds interesting!!!
See this article for some amazing examples of where stitching with a T/S lens is more than a technical exercise: The First 17mm Tilt-Shift shots Darwin Wiggett

That said, most modern, dedicated stitching software (including Photoshop's "photomerge" function) will automatically "undistort" your images before stitching them together and allow your choice of perspective projection determine how little or how much distortion you want to see in the results. With a T/S lens, no automated "stitching" is really needed other than overlaying the two images side-by-side.
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