Tilt/Shift Helper Charts

[Wil_Bloodworth]

For those of you who shoot landscapes or anything that requires a lot of depth-of-field, you're probably using a tilt/shift lens. Well, determining the precise amount of tilt or shift needed can be a little bit difficult "on the fly".

There are charts out there but they're usually in millimeters... and my brain "don't work too good" in millimeters like all of our friends' do across the big pond. Therefore, I've created a little chart that uses feet as the unit of measure.

To calculate the angle (number of degrees) of tilt (up/down) or swing (left/right) required to get everything in focus from near to infinity, you have to take the arcsin of the focal length divided by the distance from the "object plane" to the lens axis. Sounds complicated but think of it this way, if your focal plane is the ground you're standing on, then the "object plane" is the ground. So that last part of the equation would be the distance from the ground to the middle of your lens. If your camera is mounted on a tripod, you're using a 24mm t/s lens, and it's roughly 5 feet (which is 1524 mm) off the ground, then the formula is arcsin(24 / 1524) = 0.015748683... but that number is in radians. To convert it to degrees multiply it by 180 and divide by Pi. 0.015748683 * 180 / 3.14159235 = 0.90233317... or 0.9 rounded.

Formulas in the field are a PITA so just carry a chart instead.

Here are the charts... do with as you like.

I've included a link to the Excel spreadsheet I created to create these charts... play with them if you like: Excel Spreadsheet

17mm (for the Canon guys)








Enjoy!

- Wil

[KdLaneJr]

Your post has caused me to pause, reflect, review and contemplate the difference between shooting landscapes and shooting large groups with a tilt-shift lens. What I really want.. is to tilt the DOF across the three or four rows (or more, in the case of stadium seating) of folks I'm photographing and have them all crisply in focus without going greater than f/16

I've reoriented my 24mm tilt so it's parallel to my shift. This allows me to not only lay my focus plane along the angle of my group, but to also control the amount of foreground. I've done one set of group shoots this way so far and I like the results.

I'm not sure why excel outputs the arcsine in radians, requiring conversion to degrees. When I use a standard calculator, in degree mode, it's only necessary to take the arcsine of the lens (mm) divided by the height above the ground (or distance from the plane I desire to start being in focus via the wedge shaped DOF, in mm's) to get a degree setting to start at.

[Wil_Bloodworth]

Ken,

I would assume that since you're using your calculator in degree mode, it is already doing the conversion for you.

Interesting idea about how your're shooting the group shots. I'll have to give that some thought. Thanks.

- Wil

[venchka]

Thanks Wil! Now, for your next assignment, how about 4x5 cameras and 75mm, 90mm,125mm, 150mm, 180mm, 210mm and 250mm lenses. Please!

Did I miss any lenses Kevin & Westley?

[Wil_Bloodworth]

You're welcome Wayne. Unless I am mistaken (which has been known to happen), the formula is constant regardless of the size of the film plane (35mm, 4x5, 5x7, 8x10, etc). If that is the case, then here are those charts:















- Wil

[Wil_Bloodworth]

I'm currently reading Bob Wheeler's "View Camera" paper and I'll get back to you if the formula is different. Here's the paper: http://www.bobwheeler.com/photo/ViewCam.pdf

- Wil

[Wil_Bloodworth]

Wayne,

Yes, these charts hold for any size of film/image plane. Here is a great read that confirms this: http://www.trenholm.org/hmmerk/VuCamTxt.pdf

And here is another good (closely related) link: View Camera Focus

If you use the easier calculation of Angle = f / 5 * j where f = focal length in mm and j = distance from lens axis to the focal plane (ground) in feet, you'll get close to the precise value. For example, I've added the f/5*j formula to the 90mm chart:



If you find yourself in the field without the chart, the f/5j formula will definitely do!

- Wil

[Murph]

Thanks.

[Wil_Bloodworth]

You're welcome Murph!

- Wil

[bomboman]

Thanks.

[venchka]

Thanks Wil.

[Wil_Bloodworth]

Absolutely! Let me know if this comes in handy in the field!

- Wil

[jeffkohn]

Charts like these are a big help. I keep electronic versions on my phone rather than printed copies. The only thing that can get tricky is determining where your desired plane of focus is, because along the ground is not always what you want. Sometimes I want my DOF to cover a foreground subject that's a foot or two off the ground and very close to the camera, as well as some trees or other features in the mid-ground. In that situation it's easy to use too much tilt and have things be soft at the top of the frame. Live-view is a big help in checking that you're getting the result you want.

[Wil_Bloodworth]

Thanks for pointing out that issue Jeff. I wouldn't have thought about that unless you mentioned it.

- Wil

[Lexie]

Thanks!! I the 17mm Tilt/Shift lens!...........Sort of! Seriously, I do love this lens, but it takes LOTS of practice to get EVERY THING correct!