I’ve been testing a lot of different SD cards with the Sony FX6. I have been a long time user of Integral, Lexar and SanDisk cards and generally found them to perform well and to be reliable. But in my search for affordable v90 SD cards I came across a good deal on the ProGrade v90 64Gb SD cards.
I hadn’t ever used the ProGrade brand before and their pricing almost seems too low. But I decided to purchase one to test. Well I have not been disappointed. The card performs very well and has no problems at all with all of the XAVC-I frame rates up to and including 60fps.
If you try to use it to record UHD at 100 or 120fps you will get an “unsupported media” warning but the camera will try to record to the card. Most of the time the recording will be OK provided you keep the duration short and don’t try to stop and then restart recording too quickly. Of all the SD cards I have tried this seems to be one of the best.
However you will still see recording failures with this card at 100 and 120fps. Often resulting in the card suddenly becoming completely full. So I still would not recommend relying on any SD card for 100/120fps UHD. But, as I have said this is one of the better cards that I have come across and given the low price it seems like a winner.
Other cards I have been using successfully with the FX6 are:
Integral Ultima ProX v90 for all codecs including XAVC-I up to 60fps.
Lexar 1667x Professional v60 for all codecs including XAVC-I upto to 30fps.
Sony Tough CFExpress Type A 80GB for all recording modes and formats including UHD 100/120fps.
This came up on facebook the other day, how long do SD cards last?
First of all – I have found SD cards to be pretty reliable overall. Not as reliable as SxS cards or XQD cards, but pretty good generally. The physical construction of SD cards has let me down a few times, the little plastic fins between the contacts breaking off. I’ve had a couple of cards that have just died, but I didn’t loose any content as the camera wouldn’t let me record to them. Plus I have also had SD cards that have given me a lot of trouble getting content and files off them. But compared to tape, I’ve had far fewer problems with solid state media.
But something that I don’t think most people realise is that a lot of solid state media ages the more you use it. In effect it wears out.
There are a couple of different types of memory cell that can be used in solid state media. High end professional media will often use single level memory cells that are either on or off. These cells can only store a single value, but they tend to be fast and extremely reliable due to their simplicity. But you need a lot of them in a big memory card. The other type of cell found in most lower cost media is a multi-level cell. Each multi-level cell stores a voltage and the level of the voltage in that cell represents many different values. As a result each cell can store more than one single value. The memory cells are insulated to prevent the voltage charge leaking away. However each time you write to the cell the insulation can be eroded. Over time this can result in the cell becoming leaky and this allows the voltage in the cell to change slightly resulting in a change to the data that it holds. This can lead to data corruption.
So multi level cards that get used a lot, may develop leaky cells. But if the card is read reasonably soon after it was written to (days, weeks, a month perhaps) then it is unlikely that the user will experience any problems. The cards include circuitry designed to detect problem cells and then avoid them. But over time the card can reach a point where it no longer has enough memory to keep mapping out damaged cells, or the cells loose there charge quickly and as a result the data becomes corrupt.
Raspberry Pi computers that use SD cards as memory can kill SD cards in a matter of days because of the extremely high number of times that the card may be written to.
With a video camera it will depend on how often you use the cards. If you only have one or 2 cards and you shoot a lot I would recommend replacing the cards yearly. If you have lots of cards either use one or two and replace them regularly or try to cycle through all the cards you have to extend their life and avoid any one card from excessive use which might make it less reliable than the rest.
One thing regular SD cards are not good for is long term storage (more than a year and never more than 5 years) as the charge in the cells will leak away over time. There are special write once SD cards designed for archival purposes where each cell is permanently fused to either On or Off. Most standard SD cards, no matter how many times they have been used won’t hold data reliably beyond 5 years.
I recently reviewed the rather excellent Sonnet QIO I/O device that allows you to very quickly ingest material from SxS cards, P2 cards as well as SD cards to your computer. Along with the QIO I was sent a Sonnet SDHC to SxS card adapter to take a look at. Now I’m going to lay my cards on the table here and say that I strongly believe that if your going to shoot with an XDCAM EX camera you should be using SxS cards in order to get the best possible reliability. However as we all know SxS cards are expensive, although a lot cheaper now than they used to be, I remember paying £600 for an 8Gb card only 4 years ago!
So ever since the launch of the XDCAM EX cameras, users including me have been trying to find alternative recording solutions. I found that it was possible to use an off-the-shelf SD card to express card adapter (the original Kensington Adapter) to record standard frame rates on class 6 SD cards in the EX cameras. However the SDHC cards stick out of the end of the generic adapters so you can’t close the doors that cover the card slots in the cameras. Following that initial discovery various companies have brought out flush fitting adapters that allow the use of SDHC cards. Then about two years ago Sony openly admitted it was possible to use an adapter in the cameras and released their own adapters (MEAD-SD01 and MEAD-MS01) as well as making some firmware changes that made using adapters more reliable. The key point to consider when using an SxS adapter and SD cards is that the media, the SD cards, are consumer media. They are produced in vast quantities and the quality can be quite variable. They are not made to the same standards as SxS cards. So I choose to shoot on SxS whenever possible and I’ve never had a single failure or unexplained footage loss. BUT I do carry a couple of adapters and some SD cards in my camera kit for emergencies. You never know when you might run out of media or find yourself in a situation where you have to hand over you media to a third party at the end of a shoot. SDHC cards are cheap and readily available. You can buy an SDHC card just about anywhere. I’d rather switch to SDHC cards than try to do a panic off-load to a backup device mid-shoot, that’s a recipe for disaster!
Sonnet SDHC adapter for SxS Camera Slot
Anyway… on to the Sonnet SDHC to SxS adapter. It feels as well built as any other adapter on the market. It is mostly metal with plastic end pieces that are made from a nice high quality plastic. I have other adapters that use a very brittle plastic and these can break quite easily, but this one appears to be well made. The SDHC card slots into a sprung loaded slot in the end of the adapter making a reassuringly positive sounding click when it’s latched in place. Once inserted the SDHC card is slightly recessed into the adapter. This is good as it helps prevent the SDHC card from being released from the adapter as you put the adapter into the camera. It means that as you push the adapter into the camera you are pushing on the end of the adapter and not on the SDHC card like some other adapters I have used. To remove the SDHC card you simply push it quite firmly, further into the adapter until you hear another click and it then pops out far enough to be pulled out. This is certainly one of the better made adapters that I have come across.
To test the adapter I used some Transcend class 6 SDHC cards as well as some Integral Ultima Pro class 10 SDHC cards. I used the adapter in my PMW-F3 with firmware version 1.10 as some user have reported problems with other adapters and this firmware revision. I was able to completely fill the cards shooting using S&Q motion at 50fps or 60fps using long and short clips with lots of motion. This is I believe the toughest test for these adapters as the recording bit rate is close to 70Mb/s. I had no issues at all with either type of SDHC card and there was very little delay between finishing a recording and being able to start the next, a good indicator of the cards high performance. I also tested recording very long clips to ensure that there would be no issues when the camera breaks the recording into 4Gb chunks. Again, no problem.
So if you are going to use SDHC cards and an SxS adapter I would suggest you consider the Sonnet SxS adapter. It’s certainly cheaper than the Sony adapter. Sonnet are a large business with a wide range of products and a global distributor and dealer network, so you should have no problem finding a local supplier.
This a recurring question that I get asked about time and time again. The main problem being that the SD pictures, shot with an HD camera look soft. So why is this and what can be done about it?
Well there are several issues to look at. First there is camera optimisation. Sadly what works for HD doesn’t always work well for SD. Secondly there is the downconversion process. If your shooting HD and simply outputting SD using the cameras built in downconverter than you really don’t have many options but if your using a software downconverter you may be able to improve the results your getting.
Starting with the camera, what can you do? Well first off let me say that a camera optimised for HD will always be a compromise when it comes to SD. As the native resolution of HD cameras increases then the problem of getting good looking SD actually gets worse. The problem is that a good high resolution camera will normally only have a very small amount of artificial sharpening via the detail or aperture circuits, because in HD it will look nice and sharp anyway. SD cameras and the SD TV system with it’s inherently low resolution and soft pictures has always relied very heavily on detail enhancement to try and make the pictures appear sharper than they really are. When you take the minimal additional sharpening of an HD camera and downconvert it to SD it all but disappears, the end result is a soft looking picture. There is no easy fix for this, you can either add additional extra thick detail correction edges to the HD pictures, which risks spoiling the HD image or you can add additional detail correction in post production. On a Sony camera the thickness of the detail correction edges is controlled using the “frequency” setting. Setting this to a negative number will thicken up the detail edges, very often you need to go all the way to -99 to get an appreciable difference. As an alternative you can add extra sharpening or detail correction in post, after the downconversion process. This is the way I would go whenever possible as I don’t want to compromise my HD pictures for the sake of the SD images.
The second issue is the quality of the downconversion. A simple rescale from HD to SD rarely works well as it can create a lot of aliasing. Aliasing is the result of taking too much detail and trying to record or represent it with too few pixels. See this article for more on aliasing. Imagine a diagonal line running through your image.
Diagonal Line Sampled in HD
If you sample it at a high resolution, with your HD camera then the line looks reasonably good as you can see in the diagram to the left.
Simple SD Downconversion
If you then take that HD captured edge and simply scale it down to SD, you quarter the number of samples and the end result is a jagged, stepped line. Not pretty. In addition, if the line moves through the image it will flicker and “buzz”. This is far from ideal.
Same Line, Blurred Before conversion to SD
A better approach is to blur the HD image before down converting using a 4 pixel (or similar) blur, or to use a downconversion programme that will include smoothing during the conversion. The final image shows the kind of improvement that can be gained by softening the image before down conversion. The blur around the edges of the line soften it and make it appear less jagged. This will result in a much more pleasing SD image. Next you then add in some detail correction to restore the apparent sharpness of the image and viola! A decent looking SD image from an HD source. In compressor to get a good downconversion you need to activate the advanced scale tools and use the “better” or “best” scaling options.
Ever since the release of the XDCAM EX cameras users have been having problems getting good looking SD pictures out of downconverted HD.?Why is this and what can be done about it? This is an issue that effects all high resolution HD cameras and is not unique to the EX’s. There are two key issues. The first is the way basic software converters handle fields in interlace material and the second is the amount of information in an HD image that must in effect be discarded to get a SD image.?At first glance you would think that starting off with lots of picture detail would be a good thing, but in this case it’s not. Let’s see if I can explain.?Imagine that you have something in you HD picture that over 4 pixels goes from light to dark, in Hd you get a gradual transition from light to dark and all looks good. Now what happens when you take those 4 pixels and convert them to SD. The 4 pixels become just 2 and instead of a stepped change from light to dark the picture now goes instantly from a light pixel to a dark pixel. If these pixels were the edge of a moving object, as it moved the pixels would be switching instantly from on to off and unless the object moved at exactly one pixel per frame you will get a flickering effect. Clearly our nice gradual transition from light to dark has been lost and if there is any motion we may now be seeing flickering edges. Niether of these look good.
Take a look at these images:
Original Frame showing box with area of interest
Original HD Image
Same image, downconverted to SD
As you can see the down converted SD is very blocky and there is some strange patterning (aliasing) going on amongst the bricks of the houses in the background. This does not look good and if there was motion the brickwork would shimmer and flicker.
So what can be done?
Well the best way to improve the SD down conversion is to soften the HD image before it is down converted to prevent this single pixel light to dark switch from happening. You need to end up with an SD image where you go from full light to full dark over at least 3 pixels to prevent flicker (Twitter).
How much you will need to soften you HD by will depend on how sharp it is to start with. Simply turning down the cameras detail settings can be a big help, but even then the best results are often obtained by applying some kind of blur filter in post production. In FCP I find the flicker filter works quite well. As you can see from the frame grab below the difference in the quality of the downconvert is quite striking.
SD Image created by adding blur to HD before conversion.
I have also found that another problem is that the detail settings on an HD camera are not optimised for SD. The detail correction edges created in HD are very thin and when these are down converted to SD they all but disappear and can cause further aliasing. The solution is to make the detail correction edges thicker (on an EX turn detail frequency down to -60 to -99) but this then looks ugly in HD. The bottom line is that a camera optimised for HD works best in HD and SD will be a compromise.
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