We recently added the Sony PXW-Z100 to our rental catalog, and one of the first things we wanted to test when we got it out of the box was real-world performance with N-series and S-series XQD cards. Since S-series cards are, at the moment, much more expensive than N-series cards, we wanted to know what that extra cost was buying, in performance terms. A scarcity of supply has driven the price of S-series cards up even further over the last six months. We also wanted to clear up some of the confusion around XQD card speed ratings in general. At one point, Sony offered H-series cards (with speeds similar to N-series), but those have been discontinued, so we did not test them here. The S-series cards come in several varieties, rated by their read speeds (which don’t necessarily correlate with write speeds). The S-series card we tested was the faster 180 MB/s variety, but Sony claims the 168MB/s S-series card is fully compatible with all Z100 video modes as well.
For our test, we used two N-series 64GB Sony XQD cards and one S-series 32GB Sony XQD card. We recorded with a Sony PXW-Z100 with firmware version 1.01. Each card was formatted in-camera before each test. As of this firmware version, the camera only supports recording in one codec, XAVC, the same format used in higher-end cameras like the Sony F55.
For the first test series (Test A) we recorded clips in mixed lighting, on a tripod with manual exposure and gain set to 0dB. For the second test series (Test B), we recorded clips in a very dark room, handheld, zoomed in to max, walking around, with gain at 18dB. We felt this was probably the most likely to max out the PXW-Z100’s bitrate, and represented a worst-case scenario for the cards. A test was marked as a pass (✔) if the camera recorded successfully for 6 minutes, and a fail (✖) if recording was automatically stopped. We tested each more than once, and used two different N-series cards, but we got identical results with each repeat test.
For all settings of the camera, the N-series card returned a message “Not Guaranteed Media,” and for all settings with the S-series card, there was no message. All of our failed tests stopped recording within the first 30 seconds of the clip.
|N-Series Card||S-Series Card|
|Guaranteed||Test A||Test B||Guaranteed||Test A||Test B|
|1920×1080 all framerates||✖||✔||✔||✔||✔||✔|
A quick peek at the file sizes indicated that the same 600Mb/s bitrate was reached for the 4096×2160 60p and 3840×2160 60p settings under all test conditions. To put it another way: the bitrate is based only on the video size and framerate, not what is being recorded.
The upshot is, if you’re recording in HD, or in 23.97p framerates, paying extra for the S-series cards will only buy you peace of mind. If you’re looking to stay budget-conscious, or want to wait out investing in extra media until the price drops, N-series cards may be the way to go. But N-series cards simply can’t handle 4K at framerates greater than 24p, yet. To keep things interesting, Sony is expected to support writing lower-bitrate formats AVCHD and XAVC LongGOP with a scheduled firmware update. The firmware update is also expected to enable the single SD/MemoryStick card slot, which is completely unused in the current version. For shooters comfortable with AVCHD files, XQD cards may become completely unnecessary after the update.
Posted by Jon Kline