This comes up so many times, probably because the answer is rarely clear cut.
Here’s a short clip to keep you going until later in the week when I will upload the full length version of my video “Dancers on the line” shot with the new Sony PXW-X70 camcorder. As well as the film there will be a behind the scenes video with some insight into what the camera is like to shoot with and how the images look. It’s all good stuff, this is a great little compact handycam and a pretty big step up from the AX100.
It has a nice big 1″ size sensor, built in ND filters and a nice power zoom lens. It records XAVC long GOP 10bit 422 at 50Mbps at up to 60fps. Also has AVCHD and standard definition DV. The ergonomics are brilliant, clearly Sony have done a lot of works on this area and it a delight to operate run and gun or when your pressed for time. You get great battery life and the pictures are pretty amazing for a compact handycam. You can even dial in your own picture profiles for a custom look. Dual SD card slots allow for relay recording or dual card recording, there’s an full size SDI and HDMI out too. LAst thing for now… it’s 4K ready. There will be a paid upgrade to 4K option in the first half of next year. More details to come as the week progresses.
Here’s the press release from Sony.
Basingstoke, July 29, 2014: Sony has today launched the 4K-ready PXW-X70, the first compact XDCAM professional camcorder ever produced. Expanding the popular file-based XDCAM family to a new smaller form factor and lower price point, Sony has combined stunning picture quality, speed of shooting and robust performance into a package which is ideal for a wide range of applications from news gathering and documentary to events work.??
The PXW-X70 features a 1.0 type Exmor® R CMOS Sensor with a resolution of 20 megapixels. The sensor, which is even larger than the Super 16mm film frame, delivers high resolution and fantastic low light performance, as well as offering more depth of field control as demanded by today’s diverse shooting requirements. The new camcorder has the ability to record High Definition in XAVC Long GOP, enabling 422 10-bit sampling at 50 Mbit/s. This in-turn supports a broadcast-quality workflow, increasingly adopted by productions in many different professional applications.
This addition to the expanding next generation XDCAM family follows the recently announced PXW-X180 and PXW-X160 and builds upon Sony’s successful heritage of compact professional camcorders. The PXW-X70 is the first professional compact camcorder from Sony to include Wi-Fi-enabled control via Smart Phone or Tablet using the Content Browser Mobile application. An upcoming release will also provide customers with the ability to upgrade the PXW-X70 to record in 4K Ultra High Definition, with file transferring, and live video streaming capabilities.
“This first compact member of the XDCAM family brings the performance and workflow benefits associated with XAVC to an even wider range of shooting scenarios,” said Robbie Fleming, Product Marketing Manager, at Sony Professional Solutions Europe. “Over the past couple of years we’ve seen the broadcast industry really embrace the picture quality benefits associated with large sensors; the one-inch sensor at the heart of the PXW-X70 sets a new standard for colour, depth and texture in a professional compact camcorder. Coupled with the ability to upgrade to 4K, this represents a multipurpose, future-proof option for customers looking for a tough camcorder which doesn’t compromise on image.”
Key features of the PXW-X70
• 1.0 type Exmor® R CMOS Sensor and Carl Zeiss Vario Sonnar T* lens for stunning picture quality. High sensitivity and fantastic resolution with 14.2 million effective pixels delivers striking detail and colours, even in low light conditions. The lens offers a 12x Optical Zoom, which can be increased to 24x with Clear Image Zoom while retaining full resolution thanks to Super Resolution Technology. Zoom performance can be doubled at any point with a Digital Extender by up to 48x.
• Compact, lightweight XDCAM camcorder packed with adaptable professional functions. The PXW-X70 weighs less than 1.4kg, including the XLR handle unit, battery (NP-FV70), lens hood and large eye-cup. It offers professional interfaces such as 3G-SDI and HDMI output connectors plus an XLR x 2 handle unit with zoom lever. Other professional features include a manual lens ring that can intuitively control zoom and focus, ergonomic palm grip with large zoom lever, two SD memory card slots for backup, simultaneous and relay recording, and a three-level switchable ND filter.
• Breadth of recording format capabilities. Provides multiple choices depending on application required, including XAVC, AVCHD and DV® file-based recording. When recording in XAVC, the PXW-X70 uses the MXF file format, efficiently compressing full HD (1920 x 1080) resolution using the MPEG-4 AVC/H.264 CODEC. Image sampling is 4:2:2 10-bit with high-efficiency Long-GOP compression at 50 Mbps, 35 Mbps or 25 Mbps.
• Built-in Wi-Fi control functionality for monitoring and remote control versatility. Near Field Communication functions enable easy, one-touch wireless LAN connection to a smartphone or tablet, while the Content Browser Mobile application allows confirmation of shot angles and operation of the camcorder by remote, including field angle setting, spot focus and iris adjustment.
• Upcoming announcements to add even greater, future-proof functionality. Sony is set to make upgrades to 4K and file transfer and streaming by Wi-Fi function available for the PXW-X70 in the coming months.
I was lucky enough to get to spend some time with a pre-production Sony PXW-X180 here in Singapore. I put it through it’s paces shooting around the botanical gardens, China town and Clarke Quay.
For a 1/3″ camcorder it produces a remarkably good image. Really low noise, very clean images, much better than anything I have seen from any other 1/3″ camcorder. The 25x zoom is impressive, the variable ND filter is very clever and it might seem trivial but the rear viewfinder was very nice. It’s a very high resolution OLED, much, much better than the LCOS EVF’s found on many other models.
The zoom lens has proper manual calibrated controls with end stops, much like a PMW-200. The ability to use a multitude of codecs is fantastic and perhaps better still is the fact that you can use SDXC cards for XDACM or XAVC at up to 50Mb/s, so even XDCAM HD422 can be recorded on this low cost media. This will be great for news or other situations where you need to hand off your media at the end of the shoot.
A more in depth review will follow soon, but for now here’s the video. Un-graded, un touched, straight from the camera footage. Looks very nice if you ask me.
I kind of feel like we have been here once before. That’s probably because we have and I wrote about it first time around.
A typical video camera has a special filter in it called an optical low pass filter (OLPF). This filter deliberately reduces the contrast of fine details in the image that comes from the cameras lens and hits the sensor to prevent aliasing, jagged edges and moiré rainbow patterns. It’s a very important part of the cameras design. An HD camera will have a filter designed with a significant contrast reduction on parts of the image that approach the limits of HD resolution. So very fine HD details will be low contrast and slightly soft.
When you shoot with a 4K camera, the camera will have an OLPF that operates at 4K. So the camera captures lots of very fine, very high contrast HD information that would be filtered out by an HD OLPF. There are pro’s and con’s to this. It does mean that if you down convert from 4K or UHD to HD you will have an incredibly sharp image with lots of very fine high contrast detail. But that fine detail might cause aliasing or moiré if you are not careful.
The biggest issue will be with consumer or lower cost 4K cameras that add some image sharpening so that when viewed on a 4K screen the 4K footage really “pops”. When these sharpened and very crisp images are scaled down to HD the image can appear to flicker or “buzz”. This will be especially noticeable if the sharpening on the HD TV is set too high.
So what can you do? The most important thing is to include some form of anti-aliasing to the image when you down scale from 4K to HD. You do need to use a scaling process that will perform good quality pixel blending, image re-sampling or another form of anti-aliasing. A straight re-size will result in aliasing which can appear as either flicker, moire or a combination of both. Another alternative is to apply a 2 or 3 pixel blur to the 4K footage BEFORE re-sizing the image to HD. This seems a drastic measure but is very effective and has little impact on the sharpness of the final HD image. Also make sure that the sharpening on your TV is set reasonably low.
I previously wrote about this very same subject when HD cameras were being introduced and many people were using them for SD productions. The same issues occurred then. Here are the original articles:
Remember to take a look in the TECH NOTES for info like this. There’s a lot of information in the XDCAM-USER archives now.
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.
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.
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.
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.
I was reminded of this by Perrone Ford on DVINFO.net. With HD cameras compared to SD cameras the depth of field appears shallower. Why is this and why is it important?
Visually depth of field is the loss of focus as you move away from the object that you have focussed on. If you have two cameras, one HD and one SD and they both have the same lens at the same aperture along with sensors of the same size then the change in focus with distance for both cameras will be exactly the same. However with the HD camera, because the image is sharper to start with, any small changes in focus will be more apparent than with the softer picture from the SD camera. So visually the HD camera will have a shallower depth of field. Now if you take that HD image and convert it to SD then the depth of field appears to increase again. This can be calculated and measured and is defined by the “circle of confusion”
So why is this important? Well lets look at what happens when you shoot an interview or face. The human brain is very good at looking at faces, we “read” faces day in and day out, taking in expressions, skin tone and subtle changes. We use these tiny visual cues to gauge emotion and see how someone is responding to the things that we do. Because of this any imperfection in the look of a face in a video tends to stand out (thats also why you normally expose for faces). With HD it’s quite possible to have a shot of a face where the tip of the persons nose or their ears are in sharp focus while the eyes are slightly soft. With an SD image we would be unlikely to notice this because of the greater depth of field, but HD with it’s visually shallower DoF can show up this small difference in focus and our brain flags it up. Very often you see the HD face and it looks OK, but something in your brain tells you it’s not quite right as the eyes are not quite as sharp as the nose or ears. So this apparently shallower DoF means that you can’t just focus on a face with HD but you must focus on the eyes, as that’s where we normally look when engaged in a conversation with someone.
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:
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.
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.
OK, here’s my take on the situation.
If money is no problem then the safest bet is to purchase a good quality HD lens, expect to spend at least £8k.
If you budget is restricted then the situation is much less clear. There are now several low cost 2/3? HD lenses designed for cameras such as the Panasonic HPX500. In my opinion these lenses are just not worth the money. They might be cheap (£4k ish) but the one’s I’ve played with have been pretty grim, suffering from lots of CA and soft corners.
If your on a tight budget the best thing you can do is take your camera to a good dealer and go through their second hand lenses, trying them on the camera. Check for resolution (use a chart), corner softness, CA and contrast. I did this and ended up with a Canon 16x8x2 IF lens. I found that lenses with lower zoom ratios tended to be better than those with higher ratios. I’m really pleased with my lens and when compared to the latest HD equivalents I can not tell the difference in real world use. It certainly outperforms all the budget HD lenses I’ve tried.
One interesting thing that I have discovered in my research into this subject is that Contrast is what makes the biggest difference in lens performance, not simply resolution as one might expect. Visually the next thing you notice is CA. This is a tough one as when you increase the resolution or sharpness of a lens you also tend to increase the CA.
Until lens manufacturers start to release MTF curves for their lenses the only thing we have as buyers to go on is the advertising blurb. It’s easy for a manufacturer to claim improved performance or new glass or other technology, but without accurate MTF curves it’s all pretty meaningless. You would only need the tiniest resolution improvement to be able to claim that you new HD lens range is sharper than your SD range, it could just be a fraction of a percent difference.