P.C. Lenses – More than just Perspective Control!!

As I mentioned in a previous blog, Perspective Control lenses such as my Canon 17mm TS-E f4 or 24mm TS-E f3.5 Mk II, ARE primarily used to control perspective in an image, especially when dealing with architectural subjects. Although I personally  favour the lens approach to controlling perspective, as I pointed out, there are several software solutions available that can also do an equally good job, with a few caveats. That being the case, it would be nice to know of other uses for such expensive ‘lumps of glass’ in particular as P.C. lenses are known for both there robust construction and overall high optical quality.

Read any lens review and one of the first things that becomes apparent, especially with wide angle lenses, is that lenses are not equally sharp across the whole frame, with image softness as well as lateral chromatic aberration (colour fringing) becoming more apparent, and less correctable the closer you get to the edge of the frame. Although stopping down a lens may help with image softness and longitudinal chromatic aberration, lateral chromatic aberration will still be visible towards the corners of the image especially in high-contrast areas, the wider angle the lens the greater the problem.

P.C. lenses have been designed to have a much larger image circle than conventional lenses due to the amount of shift such lenses are capable of. Also as such lenses would often be shifted to maximum in use, it was important to still maintain as high an optical quality as possible at the edges of the frame, especially as architectural subjects could  be full of fine detail which needs to be clearly recorder even at the edges. As both the Canon TS-E lenses have a 12mm shift, and used on a full frame 24x36mm sensor camera, I should be able to capture an image area of up to 48x36mm or 60x24mm depending on the lens and camera orientation, without moving the actual camera at all.

Having first used the original Canon 35mm TS lens back in the 1980’s with considerable success using slide film, so when film scanners became available in the late 1990’s, I had takes some panoramas again using slide film, which I scanned then attempted to stitch them together in software. Stitching the scans taken with the lens un-shifted worked fine, however shots with the lens shifted would not stitch at all, producing massive stitching errors either due to lens distortion or software issues, or both. Remembering this, I decided to  play safe and do my first tests using the 24mm TS-E Mk II lens to minimise any lens errors, keeping the camera in landscape to produce up to 48x36mm images.

Being a very cold and dull looking December day I decided to work indoors so chose St Mary de Castro church’s interior, here in Leicester, knowing it to have a good range of detail as well as a variety of lighting. All the shots were taken using a Canon 5DsR, on a tripod, in HDR (5 exposures, 2 stops apart) at ISO 100, f8, then combined and stitched in PTGui Pro.

The next stage will be to try and shoot rows of images to make up a full 360˚ panorama, but that will have to wait until it gets a lot warmers as the inside of a large church in December is only marginally warmer that it is outside!

_J9A0438_DxO Panorama-Edit-Edit

(above) Taken at two lens positions. 0 shift and 12mm shift up. This is the first time I noticed just how much the side walls are bowing outwards, but then it is over 900 years old!

_J9A0493_DxO Panorama-Edit-Edit

(above) Taken at three lens positions. 12mm shift up, 0 shift, 12mm shift down.

_J9A0463_DxO Panorama-Edit

(above) Taken at three lens positions. 12mm shift up, 0 shift, 12mm shift down.

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