Several people have said that the IBIS algorithms on the a7RIV are improved over those of the a7RIII, and have cited some vague Sony marketing materials as their justification for their beliefs. I admit to some skepticism, but was sufficiently intrigued to run a test. I used a Zeiss Batis 135 mm f/2.8 lens on each camera. I set up on this target:
I used the following test conditions
I ended up with about 600 images. I developed them in Lightroom, with default settigs except for the following:
I spent an hour or so crunching the data in Excel. Here's what I got for the a7RIV:
The vertical axis is the MTF 50 in cycles per picture height. The horizontal axis is the denominator of the shutter speed -- 1/100 second is plotted as 100. The heavy lines are the mean (aka mu, aka average) values. The thinner lines are the mean minus the standard deviation (aka sigma). at 1/400 second, the results are about the same. But all lower shutter speeds aren't so hot with IBIS off. 1/200 seco0nd with IBIS off is, on average, about the same as 1/30 second with it on. I know some of you are fond of thinking about IBIS improvement in stops; the span from 1/30 to 1/200 is a bit less than 3 stops.
Here are the a7RIII results:
The improvement is somewhat less.
Here are the IBIS-on results for both cameras:
The reason that the a7RIV is sharper at high shutter speeds is that the camera has a smaller pixel aperture due to its finer pixel pitch. It's go nothing to do with IBIS. But the a7RIV curve is flatter, indicating that the IBIS is working a little better. Not night and day, but not nothing, either. Note that when things go to hell with the a7RIV, they do so more dramatically.
Because the Zeiss Batis 135 has built-in optical stabilization, neither camera is using IBIS for yaw and pitch, but they are using their stabilization algorithms. I may try again with a lens that has no built-in stabilization, but I may not, because I expect roughly the same results, and thanks to the manual alignment required, this test is labor-intensive.
Continuous shooting is not a particularly good way to minimize shake. If you use single shot shooting, you can probably do a lot better than I did, but the differences between the cameras is likely to be more or less the same.
I'd be happy to answer questions.
Jim
--
blog.kasson.com
I used the following test conditions
- AF-C, medium spot
- Continuous low drive mode
- EFCS
- Uncompressed Raw
- ISO 100
- f/4
- Exposure mode A
- Aputure 120d II LED, 12-inch parabolic reflector, remotely controlled
I ended up with about 600 images. I developed them in Lightroom, with default settigs except for the following:
- White balance set to flash
- Sharpening turned off
- Noise reduction turned off
I spent an hour or so crunching the data in Excel. Here's what I got for the a7RIV:
The vertical axis is the MTF 50 in cycles per picture height. The horizontal axis is the denominator of the shutter speed -- 1/100 second is plotted as 100. The heavy lines are the mean (aka mu, aka average) values. The thinner lines are the mean minus the standard deviation (aka sigma). at 1/400 second, the results are about the same. But all lower shutter speeds aren't so hot with IBIS off. 1/200 seco0nd with IBIS off is, on average, about the same as 1/30 second with it on. I know some of you are fond of thinking about IBIS improvement in stops; the span from 1/30 to 1/200 is a bit less than 3 stops.
Here are the a7RIII results:
The improvement is somewhat less.
Here are the IBIS-on results for both cameras:
The reason that the a7RIV is sharper at high shutter speeds is that the camera has a smaller pixel aperture due to its finer pixel pitch. It's go nothing to do with IBIS. But the a7RIV curve is flatter, indicating that the IBIS is working a little better. Not night and day, but not nothing, either. Note that when things go to hell with the a7RIV, they do so more dramatically.
Because the Zeiss Batis 135 has built-in optical stabilization, neither camera is using IBIS for yaw and pitch, but they are using their stabilization algorithms. I may try again with a lens that has no built-in stabilization, but I may not, because I expect roughly the same results, and thanks to the manual alignment required, this test is labor-intensive.
Continuous shooting is not a particularly good way to minimize shake. If you use single shot shooting, you can probably do a lot better than I did, but the differences between the cameras is likely to be more or less the same.
I'd be happy to answer questions.
Jim
--
the last word the last word - Photography meets digital computer technology. Photography wins -- most of the time.
Photography meets digital computer technology. Photography wins -- most of the time.
blog.kasson.com
