IBIS Testing: A7RIII & Zeiss 55mm F1.8

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BrentSchumer
BrentSchumer Senior Member • Posts: 3,148
IBIS Testing: A7RIII & Zeiss 55mm F1.8
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So I recently picked up a Zeiss 55mm F1.8 off of a DPReview seller and an near-mint A7RIII from eBay and am putting both through their paces. I reached out to LensRentals to inquire about the most common A7RIII failure points, and was told the following:

The most common issues that we see with Sony bodies is broken IBIS systems and EVF issues.

As long as you check those two things out to make sure they are working and that you don't see any weird pixelization I think your other tests would give you a pretty good understand on the lifespan you would be getting out of the camera.

OK, it's time to test out the IBIS!

Test Methodology

I printed out a test chart on 8"x11" paper and taped it to the wall. This is obviously an undersized target but it will suffice for subjective sharpness testing.

My very amateur setup. Keep in mind how small this target is when evaluating the results below!

I tested out the IBIS by setting the camera to F2.8 and Auto ISO and taking six sets of shots:

  • 1/50s Handheld Continuous Burst Medium (x50)
  • 1/50s Single Shot (x50)
  • 1/50s Continuous Burst Medium (x50)
  • 1/25s Single Shot (x50)
  • 1/25s Continuous Burst Medium (x50)
  • 1/15s Single Shot (x50)
  • 1/15s Continuous Burst Medium (x50)

I then pulled up nine RAW files at a time at 100% on my desktop monitor in Capture One Pro. Each photo was graded on its subjective quality:

  1. Perfect - No flaws in resolution
  2. Very Good - Not quite perfect, but very good,
  3. Somewhat Blurred - Fuzzy enough to stand out from 1& 2
  4. Very Blurred - Prominent blurring of the image

Now these ratings were done very quickly, and there was probably quality overlap (e.g. sometimes I had a tough decision, especially between 1&2). I did not run images through an MTF analyzer or anything like that.

Example of Rating 1

Example of Rating 2

Example of Rating 3

Example of Rating 4

The Results

Here is a graph of my findings:

Why yes, graphs ARE a fun use of free time!

To normalize my results, you can look at the handheld shots. For my purposes I am grouping "Perfect" and "Very Good" together, as it would be very tough to find fault with either in the real world. You can see that my handheld "hit rate" was almost 2 in 3, compared to better than 9 in 10 with IBIS enabled.

One shocking finding for me was that continuous bursts were a bit worse than single shots, completely the opposite of my intuition! Typically I tackle low-light situations by taking increasingly slow bursts, but my single shutter shots were empirically superior.

The other depressing dataset is that IBIS only afforded me about 2 stops of improvement compared to Sony's claimed 5.5 stops of IBIS benefit. Now this could be due to the quantity and nature of my handshake or the fact that I was trying to "shoot casual" without managing my breathing or bracing my arms. It also could be my overly rigorous test of a 100% zoom on 42MP photos compared to industry testing that could have been designed for 20MP or 24MP bodies.

Overall, my IBIS mechanism does not appear damaged and I now know a bit more about the limits of my gear. How does this compare to your own experiences?

Oddities

One weird thing I am running into is that about 10% of my RAW files are wonky upon import to Capture One or Sony's Editor, despite looking fine when viewed with Window's "photos."

Does this mean that there is some sort of correct embedded JPG preview and the RAW is being mangled? The culprit may be my new UHS-II card, as a bunch of images taken on the same camera with an existing UHS-I card seem to be OK. Off to do further testing...

Edit: The corrupted files were due to a defective SD card reader that somehow was mangling files on transfer.

 BrentSchumer's gear list:BrentSchumer's gear list
Sony RX100 VI Sony a7R III Sony FE 55mm F1.8 Tamron 20mm F2.8 Di III OSD
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