Some people are struggling with lens options for the Sony half inch interchangeable lens cameras. Many try to use 2/3″ lenses via the ACM-21 with disappointing results. Lenses are designed to meet certain criterion. The lenses for the PMW-EX3 and PMW-320 actually perform very well, yet these are inexpensive lenses, so why when you use a much more expensive 2/3″ ENG zoom lens can the results be disappointing?
There is a very big difference between the way most typical ENG lens focus and the way an EX1/3, PMW-320 or PMW-200 lens focusses. An ENG lens will be a Par Focal lens, a lens that maintains constant focus throughout the zoom range. This is incredibly difficult to design especially with large zoom ranges and is one of the reasons ENG zooms are normally expensive pieces of glass.
The lenses used on the EX1/EX3, PMW-320 are not Par Focal, this makes them much cheaper, the focus shifts and changes as you zoom….. But clever electronics inside the camera and lens compensates for this by adjusting the lenses focus as you zoom so that in practice the lens appears to stay in perfect focus. An electronically compensated lens like this is lower cost to produce than a sophisticated typical ENG type zoom and makes the lens compact and lightweight as well as much cheaper.
Another factor is that as you increase the resolution of a lens, trying to bring everything in to focus on an ever smaller point, you run in to more and more problems with chromatic aberrations. Different wavelengths (and thus colours) of light get bent by different amounts when they pass through a glass lens. As you make the focussed light for one single colour smaller and sharper, the other colours of the spectrum become more dispersed. As a result, generally a softer lens, for example an SD lens (lower MTF) will exhibit fewer colour aberrations than a sharper HD lens. To compensate for these aberrations lens manufactures use very exotic types of glass with different refraction indexes to try to cancel out or at least minimise CA (chromatic aberration), but this glass is extremely expensive. The higher the resolution of the lens, the more expensive the glass gets.
With a camera like the EX1/EX3, PMW-320, PMW-200 when you know the exact characteristics of the lens (as they all use essentially the same lens) instead of employing exotic glass, you can program the camera to electronically remove or reduce the appearance of the CA and this happens inside the EX1/EX3, 320 and PMW-200 etc.
Next you must take in to account pixel size. In simple terms to work with the resolution of the cameras sensor, the lens has to be able to focus a point of light small enough to hit only one pixel. A typical 2/3″ HD camera has much bigger pixels that the pixels on the 1/2″ sensor of the PMW-320. As a result a lens that is only just able to achieve HD resolution on a 2/3″ camera, will not achieve HD resolution on the PMW-320 with it’s smaller pixels, it’s simply not designed to work with such small pixels. This means that you really need an HD lens designed for the 1/2″ sensor size and the corresponding pixel size.
These factors combined mean that the standard kit lens on the EX3, PMW-320 etc appears to perform very well and it takes a much more expensive, designed for 1/2″ lens to even match this apparent performance in most cases. Perhaps the new 16x lens coming for the PMW-300 will be available to purchase on it’s own. This would offer EX3 and PMW-320 owners the option of a high performing lens with a greater zoom range, probably for less than a similar performance conventional lens.
I’ve spend a couple of days putting a PMW-320 through it’s paces. The 320 is the latest addition to the XDCAM EX line up. It’s very much like the PMW-350 which I reviewed in depth last year, the principle difference is the sensor size. The PMW-350 is 2/3? while the PMW-320 is 1/2?. The camera can be purchased with or without a lens, the supplied lens is a Fujinon 16×5.8mm HD lens that has both autofocus and manual focus. The lens mount is Sony’s standard 1/2? hot shoe bayonet, so owners of DSR300? or PDW-350?s etc can use their lenses directly on the PMW-320. As with the 350 the lens that comes with the 320 is pretty good. Nice and sharp and with a good feel to it considering the cost. It does however suffer from flare under harsh lighting and this can soften the picture a little. A good lens shade or matte box with flags would really help this lens.
Externally the 320 and 350 are almost identical. The give aways are the rubber strip under the handle, EXMOR badge on the side and lens mount ring are dark blue on the 320, black on the 350. Off the shelf the stock PMW-320 actually has more features than the 350. SD is included as standard and it can output to both HDSDi and HDMI at the same time. Buttons and switches are the same on both camera as is the excellent high resolution colour viewfinder. On switching on and looking through the menus they appear to be the same as the 350, no there surprise really, so just like the 350 instead of the pictureprofiles and Cinegammas found on the EX1R and EX3 we have Scene Files and Hypergammas more like a PDW-700 or other high end Sony cameras. Talking of the EX1R and EX3, there has been a little confusion over the sensors used in the 320. At first I got the impression that the 320 used new sensors, but I was told at NAB that was not the case and the 320 has the same sensors as the EX1R/EX3. So I was somewhat surprised when I started looking at the images from the 320 to see less noise and a different looking picture.
On the PMW-320 there is a wider range of camera adjustments compared to an EX1R. For example as well as detail settings there is also a section for adjusting the Aperture correction which can also sharpen and soften the look of the camera by boosting high frequencies. Out of the box I didn’t think the 320 was quite as sharp as my EX3. But after a few minutes on the bench and with a few tweaks to the detail and aperture settings the camera was looking very good indeed (detail -8, aperture +20). While not a quiet as the PMW-350 the 320 does appear to have less noise than an EX1 or EX3. It’s not a big difference, but every little helps. My guess there is additional signal processing going on to reduce the noise.
The use of scene files for the PMW-320 and PictureProfiles on the EX1 does make it harder to match the cameras if your using non-standard settings. It can be done, but it takes a little more work.
The power consumption of the 320 is, once again remarkably low. I was powering it with a 95Wh battery and it lasted most of the day. There are no fans to make noise and it’s very light yet well balanced. The big question on my mind when I heard about it was, why buy a 320 when you can get an EX3 for a lot less or a PMW-350 which has amazing image quality for another £2k to £3k. Well obviously the form factor is very different from an EX3. The 320 is a full shoulder mount camera, complete with slot for a radio mic that runs on V-Lock batteries. The EX3 is a semi-shoulder handy-cam running on small batteries. Both will take 1/2? interchangeable lenses, so no great difference there. But as well as the form factor, which can be very important, the PMW-320 also adds SD recording and HDMI output. There is also the small improvement in image quality to consider. I like the 320, not as much as I like the PMW-350, but it is a fair bit cheaper so could prove to be very attractive for those on a tight budget that want the shoulder mount form factor as well as those that may already have nice 1/2? lenses on their PDW-350?s or 355?s.
Click on the images below to see the full frame images. The small noise improvement is difficult to see in a frame grab. It’s more noticeable in a video clip.
Camera setup, reviews, tutorials and information for pro camcorder users from Alister Chapman.