Time to Shift Your Perspective

I bought a shift adapter recently and decided to take a few pics with it. What is a shift adapter? I am glad you asked. This device couples between the lens and body to allow the lens axis to be moved either horizontally or vertically. This allows you to make a view camera type “movement” to either correct for vanishing point perspective or to optically “move” the camera when you physically cannot. Back in the 1980s and 90s I had a Canon TS-35mm f2.8 lens. This lens allowed for a shift movement and a tilt movement as well. These are very expensive lenses. Thanks to our amazing world of digital mirrorless bodies we now have the opportunity to adapt regular lenses and make them shift lenses or even tilt and shift lenses. The shift adapter I have is well made and cost me $125. It can be used on my EOS-M with any Canon FD mount lens. I have a lot of those 🙂 They offer a wide variety of options for many cameras and lens mounts. If you want the added tilt movement those are around $300.

The primary use for a shift lens is for architecture. The issue of a leaning perspective when shooting a tall building is easily corrected with a shift lens. The first thing to understand however, is the idea of image circle. Lenses project a circular image onto either film or a digital sensor. Since we are accustomed to having our photos in squares and rectangles, film and sensors are shaped accordingly. Essentially the more rectangular the image shape the more wasted image area we have with our lens. Typically whatever the shape of the sensor the corners of it are usually right out to the edge of the image circle. This is why corners are the softest part of the image. When we use a full frame 35mm lens on a crop sensor camera or a micro 4/3 we are only utilizing a small portion of the image area projected by the lens. Even the corners are not close to the edge. This is true with a medium format film lens on a full frame sensor as well.

Companies are now offering well machined shift and tilt/shift adapters for medium format on a full frame or full frame on crop sensor and micro 4/3. You can find these on EBAY or at camera shows such as PhotoFair. I created a diagram image to help explain image circle and how it applies to shift movements. The diagram shows a gray circle and a full frame sensor image made with an old Tamron SP 17mm f3.5 lens. 17mm is very wide on full frame and moderately wide on an APS-C crop sensor. The image is uncropped taken with a Canon EOS 5D Mk II. The gray area is the actual image circle of the lens. If we had a large enough sensor we could see all of the stuff in the gray area. My feet at the bottom perhaps, the top of that tall Fir tree, more sky and more driveway, and a little more left to right as well. As you can see there is no room to move or shift the full frame image within this circle so all that extra image space is lost. If we did shift the full frame image left or right, up or down we would leave the image circle and get a vignetted image. The white rectangle loosely represents the area of the APS-C sensor on my Canon EOS-M. 17mm on that camera has a full frame equivalent of 27mm. The red lines represent the image area available to the cropped sensor by shifting the lens on the adapter either left or right. The adapter allows you to rotate for the exact same effect on a vertical axis up or down. In this case the EOS-M has an extra 60% of movement in either direction. Keep in mind that a full frame 17mm is very wide and there is some distortion and softness as you approach the edge of the image circle.  Micro 4/3 is even smaller so it will have even more room to shift.

This ability to shift can help control perspective. As I mentioned earlier the common use of this effect is to control perspective when shooting tall objects up close. Cityscapes provide an ample opportunity to put the concept to use. When taking a photo of a tall building from the street one has to tilt the camera up to get the whole structure in the picture. The moment the camera is no longer perpendicular to the ground or parallel to the building, lines appear to converge as they get further away. This makes the building seem to lean back away from the shooter. Sometimes this is a good effect. When we look up with our eyes we get the same perspective with converging lines and it helps us with depth perception. But there are times when we may not want converging lines. The only way to do it properly is to get to the middle of the building and shoot it straight on perpendicular. In the case of a 12 story building we need to be roughly six floors up, opposite the structure so we don’t have to tilt the camera up or down. Or we can use a shift lens! No fire ladder required 😉 The process is to keep the camera perpendicular to the ground and aim at the building, then use the shift feature to slide the lens up until the top of the building is included or until you run out of image circle; hopefully it is the former and not the latter.

   

I have included four images of the same building in this sequence. The first is the 17mm lens on the EOS-M without perspective control looking up at the building. Classic 🙂 The next is the same shot with the camera perpendicular; actually I was just a little off, I recommend a bubble level, I left mine in the car when I shot these 😦  The second image still has no shift movement. There are no converging lines, but the building will not fit in the frame either. There is a lot of unnecessary foreground in the second image. The third image utilizes the shift function to get the top of the building in the frame and the excess foreground is gone. All three of these images were taken from precisely the same spot with the same lens. The only downside is the utility lines in the photo. I went ahead and took a shot half again the distance closer with a super wide-angle 11mm. This made the wires go away at the expense of having a leaning building. Sometimes you just have to choose between the lesser of two problems 😉

This first set of images above, has the building in a 3/4 view. Although we can correct the convergence on the upright portion, the back of the building still has convergence. The shift can only correct one dimension. This next set of images is taken more or less face on.

   

This series shows the building in the classic lean back, proper perspective with no shift and finally proper perspective with a shift to get the whole building in the photo. All of these were taken from the same spot. Once again, my bubble level was in the car and this building is on a slight hill. I was not exactly level for these. This Tamron 17mm is a moderately sharp lens, not spectacular by any means. It has some severe vignetting near the edge, which is fairly common on ultra-wides. I made another picture up closer and deliberately at an oblique angle. I shifted the lens right to the edge to show how the ultra-wides can have severe distortion and a dramatic loss of edge resolution. It is best to avoid the absolute edge of the frame if you can. You can even see the corners are off the image circle and black. The tip of the building is distorted and very soft. The adapter I have will allow me to push beyond the image circle, so I have to be cautious about that as well.

Another possible use of the shift lens allows you to take a picture that appears to be taken from a spot that was not physically possible. For example I can be standing on the shoreline and shooting down the coast. If the coastline juts out further down into the ocean I can turn the camera towards the jut out to take it into the scene. The shoreline however is no longer running straight through the scene but is now angled towards the sea. I could leave the camera pointed exactly in the same direction and shift the lens toward the sea taking in the land form that juts out while leaving the rest of the perspective exactly as it was. I used a still life indoors as an example. The image of this living room is made from the foyer. There is no way to take a shot of the fireplace head on from the foyer. So I shot it with the camera turned to center the fireplace. There is convergence issues with the shot. When the camera is turned to correct the convergence the fireplace is off center and there is too much sofa in the picture. When shifted the convergence is cured and the fireplace is centered. To actually shoot this third image without a shift lens, I would have had to take out a wall or use and even wider angle lens and stand closer. The perspective is dramatically different and whether one prefers the camera swing or the shift, the effect remains. Two distinctly possible image perspectives without moving position.

Perhaps I will talk about tilt in another post. Get out and enjoy photograghy because it’s awesome! Be sure to mark you calander for the Winter PhotoFair down in the Bay Area. February 21st at Newark Pavilion. Check the PhotoFair website for more info.

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