I’ve been using a 49/77mm Heliopan step-up ring to mount my 77mm Heliopan variable ND filter on the Zony 55mm f/1.8 lens. The female threads in the ring had developed a burr that made threading the filter on a little tricky. Sometimes it seemed like it was on firmly, but I noticed that I could… [Read More]
Real-world a7/a7R handheld images
Enough of these charts. I’ve been asked for some real-world handheld images from the Sony a7 and a7R . Happy to oblige. I made five images with each camera, using the Zony 55mm f/1.8 lens in single-shot AF mode. Drive set to single shot to get all 13 bits. ISO 100. 1/125 @ f/6.3. I… [Read More]
Comparing sharpness in cameras with different-sized sensors
A few posts ago, I showed you the results of running slanted-edge modulation transfer function tests on the Sony a7 and a7R, both handheld. Since the cameras have different resolution, and the test results for MTF50 were in terms of cycles/pixel, I multiplied the a7R values by 1.22 so that the MTF50 results were in… [Read More]
The intellectual underpinnings of MTF analysis for handheld images, part 2
Actually, this post applies to MTF analysis in general, whether the camera is on a tripod or not. In the previous post, I said: to get the system’s modulation transfer function (MTF), we perform a Fourier transform on the system’s impulse response, or point-spread function (PSF), and throw away the imaginary part. What do we… [Read More]
The intellectual underpinnings of MTF analysis of handheld images
A few days ago, I made a post with a handwaving defense of the use of slanted edge MTF metrics for analyzing handheld image sharpness. Today, I’d like to take another crack at it, this time with more rigor. The upside? A clearer basis for the capabilities and the limitations of the technique. The downside?… [Read More]
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