mike_halliwell Posted February 25, 2021 Share Posted February 25, 2021 (edited) Z6ii Nikon | Download center | Z 6II Firmware Z7ii Nikon | Download center | Z 7II Firmware Z6ii update adds 4K 60P, with the added card details.. < CFexpress/XQD Memory Cards >A card with a maximum* data transfer rate of 250 MB/s or faster is recommended for recording and playback of movies at a frame size of 3840 x 2160 (4K UHD) 60/50p. < SD Memory Cards >A UHS Speed Class 3 or better card with a maximum* data transfer rate of 250 MB/s or faster is recommended for recording and playback of movies at a frame size of 3840 x 2160 (4K UHD) 60/50p. With added better Eye AF for both. * I guess they mean MINIMUM! Edited February 25, 2021 by mike_halliwell 1 Link to comment Share on other sites More sharing options...
ilkka_nissila Posted February 25, 2021 Share Posted February 25, 2021 I don't think there is any SD card with minimum data transfer rate of 250 MB/s or faster available. For example, Sandisk's UHS-II cards have 300 MB/s specification which refers to maximum read speed, there is also U3 which means minimum sequential write speed of 30 MB/s. There are also V60 and V90 classes for 60 MB/s and 90 MB/s minimum write speeds (Prograde makes those at least). I am sure that Nikon are referring to the most visible speed rating which is probably the maximum read speed, this is because it's the easiest figure on every card to see. Speed Class | SD Association I think the Nikon 4K 60 should produce around 36 MB/s of data, nowhere near 250 MB/s. I haven't actually tested this but am just doubling the quoted 144 Mbps for 4K in Nikons. If someone has the camera and can confirm (or give a more accurate figure) that would be welcome. :) 1 Link to comment Share on other sites More sharing options...
mike_halliwell Posted February 25, 2021 Author Share Posted February 25, 2021 I don't think there is any SD card with minimum data transfer rate of 250 MB/s or faster available. I'm guessing the incorrect use of MAXIMUM, may indicate a completely wrong set of figures written by a non-technical person...? A cut-and-paste cock-up maybe? _________________________________ I personally think Mb/sec should be completely removed from all data rate spec regarding imaging. It's an historic anachronism. Everyone (!) now works with MB. Modest JPEG 1.8 MB, monster D850 NEF 58MB. How long to transfer it down a 20Mb/s cable connection... no idea. Divide by 8 to get MB/sec is it?? Link to comment Share on other sites More sharing options...
Niels - NHSN Posted February 25, 2021 Share Posted February 25, 2021 That 4K 60p is cropped, right? Niels Link to comment Share on other sites More sharing options...
mike_halliwell Posted February 25, 2021 Author Share Posted February 25, 2021 That 4K 60p is cropped, right? Yup, cropped to DX AFAIK. 1 Link to comment Share on other sites More sharing options...
rodeo_joe1 Posted February 25, 2021 Share Posted February 25, 2021 How long to transfer it down a 20Mb/s cable connection... no idea. Divide by 8 to get MB/sec is it?? The reason for using megabits per second is a serial transfer thing. There are several protocols for serial transfer, some using start/stop bits, and some using additional parity checking or handshake exchanges. So the translation from Mb/s to useable MB/s can be anything from a simple divide by 8, to divide by 11 or 12, depending on the protocol and how many bytes there are in a transfer frame. Just FYI. Of course, most of those protocols are now obsolescent, but it takes a long time for these old 'habits' to disappear from use. Strange in an industry that thrives on change and update. Link to comment Share on other sites More sharing options...
ilkka_nissila Posted February 25, 2021 Share Posted February 25, 2021 (edited) I'm guessing the incorrect use of MAXIMUM, may indicate a completely wrong set of figures written by a non-technical person...? Typical 250 MB/s cards have adequate write speed (U3) for 4K 60 for this camera, so it makes some sense to use this figure as it is easy to find on any card. They may have decided it's too complicated to ask the user to figure out about the U and V speed classes that address the requirements of high bit rate video in a more specific way. Note also that XQD and CFexpress cards don't have minimum sustained write speeds as a specification provided by the manufacturers. Probably manufacturers should give more information about the write capabilities of their cards now that high quality video is becoming more common. Anyway, users tend to network online and pass on information about their experiences regarding video recording in these modes with different memory cards. I personally think Mb/sec should be completely removed from all data rate spec regarding imaging. It's an historic anachronism. In video bit rates, and internet connections, (mega)bits per second has stayed as the unit. Canon seem to have used V and U classes to designate requirements for SD cards for video recording on their R5. Compatible Cards (EOS R5) Edited February 25, 2021 by ilkka_nissila Link to comment Share on other sites More sharing options...
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