jcolwell Offline Dedicated FM Upload & Sell: On
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p.1 #6 · Any DOF charts for tilt lens exist ? | |
I made an Excel spreadsheet, LensTScalc, that uses the Hinge Rule (derived by Scheimpflug, see "About FOCUSING the VIEW CAMERA", http://www.trenholm.org/hmmerk/) to calculate how much tilt I need to get the horizontal ground plane in focus, as a function of focal length and height of the camera above the ground. It generally works pretty well. Note that it doesn't explicitly account for DOF variation as a function of distance from the camera.
Here's a few example images from some lens comparison tests I did recently with tilt on my Mirex M645 to EOS adapter, to help decide which of several M645 lenses I should sell. I first used the T-S spreadsheet to figure out how much tilt I should use (about 3 deg for an 80mm lens on a 1.64m tall tripod), and then dial it in on my Mirex. I didn't account for a small reduction in tilt due to the lens axis pointing down at about 30 degrees, but I was shooting at f/8, and so there was sufficient DOF. For shooting landscapes with tilt, I use the spreadsheet to get started, and then follow 'standard' LF focus techniques to focus for near and tilt for far, as it usually needs some tweaking.
The first image is the full image with an 80mm lens. The second image shows two 100% crops from the very top of the frame; on the left is f/8 with 0 deg tilt; on the right is f/8 with 3 deg tilt (from LensTScalc); both taken with M645 C 80/2.8N on 5D, 1/6 sec, ISO 400, MLU, tripod, etc. The third image shows basically the same top crop for the M645 A 150/2.8 lens; 0 deg tilt on left and 5 deg tilt on right. No sharpening, yes auto-contrast.
You can get a copy of LensTScalc at http://www.jcolwell.ca/photography/calc-info/
Remember, you get what you pay for. 



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