Monday, February 11, 2013

Extreme Depth of Field Control with Tilt Lenses


In this post, I discuss my first impressions from using a tilt adapter, a tool for controlling depth of field.



BACKGROUND
Even before I started learning photography, I've always been fascinated with photos with a shallow depth of field.  When I got my first DSLR, I was at first impressed with the shallow depth of field compared to a point-and-shoot.  But eventually I wanted a shallower DOF, so I got a fast standard zoom (the Tamron 28-75 then later the Tamron 17-50 VC).  Then I added a fast telephoto (the Sigma 50-150 2.8).  Then I upgraded to a full frame camera, with a Sigma 50 1.4 and later an 85 1.8G.

I still wanted a shallower depth of field.  One of my favorite photographers, Ryan Brenizer, uses tilt-shift lenses to achieve a very shallow depth of field (see this post).  Tilt shift lenses allow the lens to be tilted or shifted parallel to the camera body.  The capability to tilt the lens allows the photographer to either increase or decrease depth of field.  (The shift capability allows control of perspective and reflections.)  The problem is the cost, around $2000 for each lens.

When Samyang announced that they were making a tilt shift lens, I was excited.  Finally I could get a tilt-shift lens and it would be affordable!  Unfortunately, the lens was not only delayed, but in the few areas where they have been released, the price was set at around $1000.  A thousand dollars for a Samyang lens???  WTH.

I started looking at other alternatives.  First, I considered a Nikon PB-4 bellows, which has a tilt and shift capability like a view camera.  However, a bellows user told me I would be limited to focal lengths of 135mm or longer (thanks Jurgen!).  Plus it's not exactly portable.

I considered Lensbabies as well.  The thing with Lensbabies is that the blur around the subject is not from being outside the area of focus but rather because the lens has extreme spherical aberration.  To me, the blur from aberration is not the same as the blur from being out-of-focus.

After some more searching, I learned about the Arsat 80mm Tilt-Shift lens.  They have a 35mm version as well.  They are a lot more affordable than the Canon or Nikon tilt-shift lenses.  But then I read about some complaints about the image quality of the Arsat 80mm lens.

Fortunately, Arax, the company that sells the Arsat lens, also makes a tilt adapter for Nikon and Canon.

ARAX TILT ADAPTER


A tilt adapter is used with a lens to allow the lens to be tilted.



The Arax tilt adapter is made of metal and feels very solidly made. It allows up to 8 degrees tilt, and can be rotated 360 degrees. The Arax tilt adapter is available for Canon or Nikon almost all mounts:

Nikon F (AI, AIs)
Canon EOS, Canon EF
Canon FD
Minolta A (Dynax, Maxxum, Sony Alpha)
Pentax K
M42 (Zenit, Practica, etc.)
Contax
Yashica
Leica R


Because the lens will be tilted, the adapter is intended for use with a lens that has a larger image circle. The Arax tilt adapter was designed to be used with full frame 35mm cameras, therefore it uses medium format lenses -- in this case, lenses that use the Pentacon Six mount.

Fortunately there are several lenses available for the P6 mount, and many of them are affordable. The one shown here is the Mir 26B, a 45mm f/3.5 lens that uses a similar design to the Carl Zeiss Flektogon 50mm f/4.  It came all the way from Russia!
To mount the lens on the adapter, you align a protruding screw on the lens mount to the matching receptacle on the adapter. Then you rotate a ring that locks the lens to the adapter.



Mounting the lens and adapter to the camera body is the same as any other lens. You just align the adapter mount to the camera body and turn it. A couple of notes: there is a lens mount indicator on the adapter but it is slightly off. Also, because the adapter can rotate 360 degrees, it may rotate just before it is locked on the camera body -- just be sure the adapter is really locked.



To tilt the lens, there is a stepless ring that you simply rotate. The ring is marked to show how many degrees it is currently tilted. The adapter will tilt the lens in only one direction therefore to set it to the desired position, you need to rotate it as well.

To rotate the lens, you hold the adapter firmly and rotate it. It takes some force to rotate the lens / adapter. Fortunately the adapter has a couple of dimples to facilitate gripping the adapter. There are detents for twelve positions (like a clock, which makes it convenient for me to remember the position I used) although it is theoretically possible to rotate the adapter to any angle.

FOCUS AND METERING

The adapter is completely manual. I find it easiest to focus with the LCD screen in live view.

Metering is also manual, with a couple of twists (pun not intended). First, when the lens is tilted, the metering indicator doesn't seem accurate. The meter may indicate '0' even though the scene appears underexposed. Second, the metering changes as you tilt and rotate the lens, even though the actual lighting conditions have not changed. Auto ISO and TTL flash can work, although I find I generally have to adjust exposure compensation or flash exposure compensation upward.



DEPTH OF FIELD CONTROL

Now we get to talk about DoF control. How much control can we get with a tilt adapter?

Here is a test scene. I positioned three Bakugan toys on a bed of pebbles. As you can see, the red and blue Bakugan are about the same distance from the camera.



Here is the baseline shot at f/3.5.



In this shot, I decreased the depth of field by rotating the lens upward to the 12 o' clock position:


In this shot, I increased the depth of field by tilting the lens down:



In this shot, the focus was shifted to the right. Even though the red bakugan is the same distance from the camera as the blue one, it is completely out of focus while the blue bakugan is in focus.



Here I shifted the focus to the left.



Note that I was on a tripod. As I shifted the focus, there was a change to the frame.



Here is a second test scene. I changed the positions of the Bakugan so that the blue one would be farther from the camera than the red one.



Here is the baseline shot.



With the lens tilted to 9 o'clock (tilted to the left), the black and blue toys are in focus while the red one is out of focus, even though the red one is closer to the camera than the blue one (!).



Here is a slideshow showing the changes to the depth of field and the position of the frame as I rotate the adapter from 12 o'clock, clockwise.





SUMMARY

I'm very pleased with the Arax tilt adapter. The tilt capability allows me to have a lot of creative control over depth of field. With it, I can not only increase or decrease depth of field, but I can also shift it to the left or right, or even bypass some subjects.  Best of all, the adapter is reasonably priced, and so are many of the Pentacon 6 mount lenses.

I haven't had the opportunity to shoot with it for real photos but am very much looking forward to doing soReal world sample shots now posted.  Meanwhile, I got a couple more lenses for the tilt adapter: a Carl Zeiss Jena Biometar 80mm 2.8 and a Carl Zeiss Jena Sonnar 180 2.8. I will also post results of those lenses with this adapter.

UPDATE: ALTERNATIVES
There are several alternatives to the Arax tilt adapter.  Among them:
1.  Arax has a new tilt adapter that uses Hasselblad mount lenses instead of Pentacon 6 mount.
2. Arax has a fixed tilt adapter for Nikon lens to Nikon body or Canon EOS lens to EOS body.  It is fixed at 11 degrees tilt but can be rotated 360 degrees.  I'm not sure if the image circle is wide enough for full frame.
3. Kipon has a new tilt AND shift adapter for Hasselblad lenses for Canon, Nikon or Sony bodies.  It allows up to "12mm" tilt (not sure how many degrees that is), up to 15mm shift, and 360 degrees rotation.  It's a little more costly than the Arax though.

UPDATE: Real world sample shots here