Looking for answers on Photography Life lens testing. LP/PH, picture height is the camera oriented
horizontally or vertically? Frame positions Center, Mid, Corner - what percentage of the frame do
each of these occupy?
Sure thing, @jthomps. The unit is not LP/PH but LW/PH (line widths per picture height). Picture height actually refers to the longer dimension of the sensor - don't ask me why, I didn't invent the term. The camera is oriented horizontally.
The section of the chart that we analyze does not occupy a large percentage of the frame. Nor should it - if it did, the measurements could be very different within that section.
At this link from Imatest, the first image under the header "Multi-ROI summary display" shows the one region that we measure in the center, the six regions that are averaged to form our Midframe measurement, and then the four corners regions: https://www.imatest.com/docs/sfrplus_instructions3/
It's technically not even the whole red box, just the slanted line itself. (Also, we don't use the two measurements from the center of the left and right edges.)
Let me know if you have any more questions!
Hey @aaronfeldman and welcome to our forum! The links didn't show up properly in your comment because you're a new member (need two approved posts first) so I slightly modified your post. But the answer is that we always fill the frame with the test chart, so we don't take into account the nominal focal length, only the true focal length. You're right, we should be able to measure it as part of our lens testing. That would be a cool thing to try out.