HD lenses for 1/2″ Cameras like the EX3, PMW-320 and new PMW-300.

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.

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20 Responses to HD lenses for 1/2″ Cameras like the EX3, PMW-320 and new PMW-300.

  1. This article is really useful Alister. Thank you.

  2. Thank you Alister.

    Our PMW320K came with a 16x lens. The slightly longer reach is useful – just wish it had OIS like the EX1R. We leave steadyshot engaged even on a tripod – very useful at the long end. Not spotted any adverse effects. Does the PMW300 include OIS?

  3. Silver R says:

    Thanks Alister. What about using DSLR telephoto lenses instead of broadcast lenses with PMW-EX3/PMW-300? Do they produce also bad and unsharp image, because they are designed for larger sensor cameras?

    • alisterchapman says:

      Depends on the quality of the lens. DSLR lenses are designed for much higher resolutions than HD, so a good, sharp, DSLR lens can perform quite well.

  4. Michael Oates says:

    Thanks Alister. I have been debating upgrading from a PMW-200 to a PMW-300 and using my 2/3″ lenses. It would appear that I should consider the PMW-400 instead….a real 2/3″ chip camera.

  5. sergey says:

    If lens focus an image on 2/3 area, why the image will be bad on part of it of 1/2 inch area ? or size of chip affects somehow focusing ability of lens? meantime – 2/3 should give less abberation; for me the idea then 2/3 inch lens will work bad concerning the resolution on 1/2 cam looks ubsolutely unprofessional.

    • alisterchapman says:

      It’s down to the pixel size. A 1/2″ sensor will have much smaller pixels than a 2/3″ sensor. A 2/3″ lens only needs to be good enough to focus on the bigger 2/3″ pixels, so when you use it with smaller pixels the image may be soft as the lens isn’t sharp enough to focus on the very small pixels of the smaller sensor.

  6. A good Canon HJ18ex28 on an EX3 works well in my experience. But I would not assume therefore that any broadcast HD 2/3″ lenses will be good enough too.

  7. Markus says:

    Can I use a Nikon DSLR lens on a PMW-400?

  8. Daniel Miranda says:

    Hi Alisterchapman,

    first of all thanks for all the informations and tips that you give us with your videos or either blogs like this.

    i have some questions that i except you can help me , I hope so đŸ˜‰

    i recently bought MTF adapter 2/3 to 1/2 to use my CANON J17EX7.7 BIRSD DIGITAL on my SONY EX3 ( i know that is an SD lens on HD Camera ) but what i notice is that when i’m using 1.8f stop the image goes complete SOFT near of Blur Image, and my backfocus is set properly . but on the viewfinder the image appear prefect, but on the recorder footages you see those bad results.

    I wouldn’t expect that the image will come exactly like the stock lens but why so SOFT.

    the other question is i had order a Sony FS7 and thinking using the same lens on it after purchasing the adapter mtf 2/3 to emount the results will be exactly like they appearing on Sony EX3 !?

    Because the Color Aberration dont bother me but the softness yes :(

    Thanks for all

    Daniel Portugal

    • alisterchapman says:

      2/3″ lenses don’t work well on 1/2″ sensors as the pixels on the smaller sensor are much smaller, so you need a lens that can produce a much sharper projected image.

      Going the other way to a larger sensor the pixel size is less of an issue but you are looking at trying to use an SD lens on a 4K camera and that’s not really a good combination. It might be OK for HD, but will be no good for 4K. Either way it won’t look as nice as a dedicated DSLR lens or cine lens.

  9. Udayjbhaskar says:

    i have sony pmw 300 cam. what is the difrence of ex mount to e mount. what type of 1/2 inch mount suitable my cam.

    • alisterchapman says:

      They are very different mounts. E-mount is only found on Sony cameras with APS-C or larger sensors. The EX3/PMW-300 mount is specifically for 1/2″ type zoom lenses although it can be adapted to 1/” and 2/3″ B4 mounts for use with 1/2″ and 2/3″ ENG lenses. You can also get EX3/PMW-300 to Nikon or Canon adapters but in this case the field of view becomes 5x narrower so a 25mm Nikon lens on a EX3/PMW-300 is quite a long telephoto lens.

  10. maurie says:

    Hi there Alister , I realise this is a year down the track…..but…I have been using an HD Fujinon 16x lens with the acm21 adaptor on my ex3 UP UNTIL NOW, I’ve shelved this package as I have now had seven re shoots and a couple of cock ups which just lost me a client with that weird 2/3″ lens on EX3 back focus issue particularly in low light! , now instead of this I’m looking at buying a good second hand SD 1/2″ lens with acm 18 adaptor instead, what do you think of that idea mate?

    • alisterchapman says:

      There shouldn’t be a backfocus issue. Backfocus simply focusses the lens for the correct lens to sensor distance. If your focus is shifting then it means that either the backfocus isn’t correctly set (maybe the macro ring is in the wrong position) or the lens is faulty. I never had backfocus issues with an EX1 and ACM21

      • maurie says:

        Hi again Alister, can’t really tell whether it’s back focus, it’s a mysterious SOFT look which just kicks in under low light, I was wondering if it’s this ex3 compensatory thing which is trying to work against the lens? I can ride it out through the range as I go which of course is a giant pain, but I was figuring as the ex3 is 1/2″ then perhaps the 1/2″ eng lenses with adaptor might eliminate this prob as it should be reading the pixels better?? one other factor , you mentioned that the lens might be faulty….now…Fujinon here in Sydney closed down it’s maintenance dept and brought techs in from Japan…..disaster…. however, I had the hd lens in after an accident TWICE to check it over, they said they checked it both times but I still have the problem (and a lot less money in the bank) , I use this lens with my F3 and on XDCAM’s …. no problems there. Any thoughts you have would be appreciated, the work this camera does is conference type wk and the set up is perfect for long lens, I’m trying not to have to get another camera, cheers mate.

        • alisterchapman says:

          I don’t understand what you mean by EX3 compensatory thing.

          There are no optics other than a piece of clear glass in the ACM21, so any softness is down to the lens. If it’s a good high end HD lens it should reasonably well.

          A 1/2″ lens is a better match for the EX cameras with their 1/2″ sensors but it is hard to find good 1/2″ HD lenses. You might be lucky and find a very good SD lens.

  11. maurie says:

    the compensatory “clever electronics in the camera and lens” mentioned in your beginning blog…..thought the camera in trying to focus a lens which doesn’t need to be focused through the zoom range, I’m just grasping at straws here as it’s been costing me money and we all need that. I’ve just re tested ALL my eng lenses HD & SD against the native ex3 plastic jobbie and they all get a murky look to them compared to it. I have read a bit about this phenomenon from various people around the world and it seems to be luck as to whether you get a good one or not, I’m hiring in quite often and don’t have the same story with other ex3’s ….it’s very frustrating … and expensive, appreciate your thoughts, thanks very much.

    • alisterchapman says:

      When you used the supplied kit lens the camera knows what the exact zoom and focus positions on the lens are and the adds electronic compensation for known defects in the lens at those positions helping produce an image that is better than it would be without compensation. When you use any other lens you don’t get these corrections, so the quality of the image is entirely down to the quality of the lens.

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