PD: Take a look to the link posted by Rodolphe, I found it very interesting.

My french is a little rusty, but it illustrates very well what I was able to see using a flashlight - 4 blade diamond shaped iris with 2 NDs at various positions in the f4 range. I attempted to photograph it this weekend but there are so many reflections from the flashlight in the various lens elements that it's difficult to get a shot which shows the NDs - their method is certainly much more effective.

It also explains something I'd noticed occasionally in a few shots, especially one long focal length shot of a bird with water behind it - the bokeh has a noticeable geometric texture to it when there are a lot of out-of-focus highlights.

My french is a little rusty, but it illustrates very well what I was able to see using a flashlight - 4 blade diamond shaped iris with 2 NDs at various positions in the f4 range. I attempted to photograph it this weekend but there are so many reflections from the flashlight in the various lens elements that it's difficult to get a shot which shows the NDs - their method is certainly much more effective.

It also explains something I'd noticed occasionally in a few shots, especially one long focal length shot of a bird with water behind it - the bokeh has a noticeable geometric texture to it when there are a lot of out-of-focus highlights.

Sony's US patent no. 6,533,473 describes a diamond-shaped iris with two ND filters. Figures 3 and 6 in the patent illustrate the progression as it stops down. Is this what you were seeing?

http://www.google.com/patents?vid=USPAT6533473&id=U1UNAAAAEBAJ&dq=6533473

Good Work, Mike.

Are you a patent attorney : )

No, but for both the Sony camcorders and the Canon HV10 (thread titled 'HV10 - ND Gradation feature'), the patent descriptions provide more detail than is available elsewhere.

Sony and Canon have pursued different physical implementations of the iris / ND filter assembly. But the design rationale is similar -- apparently the iris can't be stopped down beyond f8 without causing diffraction problems on the sensor chip. So steps of ND filtration are added to provide the effective aperture control range that otherwise would be obtained simply by stopping down the iris to f16, without using internal ND filters.

Excellent find, Mike. I hadn't seen that document; it provides very useful information. It's an oldie, but a goodie!

Using the Google link below, you can search for terms in the text of patents -- something that isn't possible on the US Patent Office site.

Search terms such as "ND filter," "ND filter Sony" and "ND filter Canon" turn up many interesting results, both old and new, which give insight into the manufacturers' thinking, and quite a few specifics of the physical mechanisms and control schemes.

http://www.google.com/patents

Evan - I think you're seeing a two bladed iris inside the Sony - the top blade is an upside-down V and the bottom blade is a rightway-up V. This is much simpler and cheaper to produce than the nice 6 bladed iris as used on the VX, FX etc, but it does the job, albeit with less attractive highlights and flare when used into the light. Out of focus highlights are noticeably less attractive too.

The internal ND filtration of the PDX10, the HC1 etc is designed to stop the cameras working at any stop smaller than f/4, regardless of the focal length. Of course if it gets brighter than even the internal ND can soak, then smaller apertures are used - but this is seen as an emergency getUhome, as diffraction with 1"/3 chips becomes quite noticeable at f/5.6 and smaller - and especially so at the wide-angle end of the zoom.

Cameras with this undocumented internal ND often 'make up something the punter will believe' when 'display' is hit on tape replay. Panasonic are also guilty of this, displaying silly f/22 readouts on many of their cameras.

tom.

Hello again after some years,

I am using a HVR-A1 and would like to know, if anybody knows how the three (?) internal ND filkters work togehter with external ones. Has anybody used them in combination?

In addition, am I correct with the following assumption regarding the exposure steps of the A1?

f4: 0db/None ND
f4: 0db/ND2
f4: 0db/ND4
f4: 0db/ND8

Thanks,
Peter

I'm not sure if the A1 has separate ND filters - I would expect it to have a varying density filter so that the more it moves into the light path the more light is absorbed. I don't know though _ I haven't looked down into its lens.

So what happens is this. You're filming at f/2 (say) and it gets brighter. The iris closes to f/4. It gets brighter still and now the ND absorbs the light. If it gets brighter than a theoretical f/11 (with max ND in place) the iris will start to close again, or in some cases the shutter speed will shorten.

It's far better to do this yourself (film at 1/100th rather than the default 1/50th) if it's very bright and avoid the use of external ND filters altogether. They cause flare spots with such short focal lengths and reduce the hood's efficiency. Not good.

tom.

Thanks a lot Thom for you explanation and advice!

Another question is what will happen when the varying density filter work together with an IR filter or circular Pol filter I am also considering to use.

You plan to use an IR filter? Maybe you mean a UV? Whatever - the internal ND will make no difference at all - it's neutral as the name suggests. If you attach a polarisor that absorbs 1.5 stops, the internal ND will simply move to allow 1.5 more stops of light to the chips.

Before you buy the circular polarisor it's worth trying a linear polarisor. Much cheaper and will probably work just as well.

I'm reading this thread getting on for 20 years after it was started !

The reason being I have just agreed to accept an HVR-A1E , as part of a bundle of bits and pieces as a swap for a PDW-F70 XDCAM deck ; I don't expect to get the stuff until after the holidays , whenever I next see my friend who has the stuff , but I thought I'd read up on the camera here .

Like the OP on this thread , I first shot moving pictures on film , although I can hardly call myself a cinematographer ; I just started out as a kid borrowing my dad's standard 8 Bolex , then later got a Minolta Super 8 .

When I was a little older I got some very secondhand U-Matic kit , before moving on to Video-8 , Hi-8 and eventually Mini-DV with a DCR-VX700 then a VX-1000 . Later , after the two smaller cameras had died , I got a JVC GY-DV500 and a second one , then a DSR500 , which at least shot in 16:9 natively .

I moved into HD with an HVR-V1E , again a used camera , chosen because it was both small enough to use for holidays and home use , but gave good enough results to use for work from time to time . A bit later I picked up a JVC GY-HD251 .

More recently , around 2 years ago now , I spotted a PDW-F350 on eBay for a very reasonable price , and having used the same camera at work , picked it up for my own interests , I then got the F70 deck to capture from , rather than using the camera . Just last year , after we upgraded to 4K at work , I was given the other PDW-F350 from there , along with the mint PDW-F70 from the edit suite ; hence my disposing of the one I already had .

To come right up to date , although I used to shoot weddings at weekends to make extra cash when I had the VX700 and 1000 , I hadn't done any in several years . Then last month a colleague at work asked if I knew anyone who might film his sister's wedding in April next year ; I said I didn't but that I'd be happy to do it as a favour .

I have done a couple of weddings with the V1E over the 10+ years I've had it , and know it to be OK , but wanted another 'small' camera to use alongside it , so bought the cheapest HVR-Z7E I could find on UK eBay about a week ago ;. On arrival I had to sort out a couple of small issues , but I'm happy with it now , and one of the deciding factors , besides I knew it would be capable in low light ( haven't yet seen the venue ) is that it uses the same batteries and accessories I already have for my V1E .

I didn't want to use my PDWs for the wedding as I know that in low light , if you put gain on they can get noisy , besides they are just a bit too big and heavy to lug around and have to set up quickly . While I have plenty of lighting I could take along , I don't want to go OTT , besides working by myself I have limited time for setup , and at most might just put in a Paglight set to wide beam and with diffuser to lift the faces a little if at all needed , and hopefully not .

Plan is to set the Z7 up on a tripod to capture the ceremony , shooting both on to tape and capturing continuously on my Firestore FS4 HD , and using the V1 handheld for guests arriving etc . I will have an ECM-MS2 stereo mic on the Z7 to capture ambience , this will go into my audio technica field mixer and back to the camera in stereo , whilst adding a single radio microphone down near the couple , panned centre to pick up the vows etc . While the other cameras will capture on board sound , I will only use the audio from the Z7 . The big advantage of my PDWs is that they have four channel audio , but I can mix the audio from the ceremony live to get a good recording .

Anyway , when my friend was going through stuff he had to swap for the deck , he mentioned he had about half a dozen A1Es , so I agreed to take one as long as it was in good working order , and he assured me at least two of the ones he has are . My thinking being that it is small enough to be hidden somewhere for a reverse angle shot of the vows , rings etc ( although I will try to place the Z7 on the tripod where it can also capture that ) , and since I have three Firestores , all can be left running to capture the full ceremony without missing anything .

Now that I'm reading up and learning about the A1 , I have found out a few things I hadn't considered about the camera - first it uses different batteries than the V1 and Z7 ; a nuisance but I will just make sure I get a few , besides I may be able to plug in and use mains power . The business about auto exposure is also a minor inconvenience , but it is very much going to be a 'C' camera and only used for a few cut-ins , as long as the image quality is not markedly inferior to the other two cameras .

From my perspective , the main benefit of the A1 is its small size , and there have been plenty of comments about its excellent picture quality .

I do appreciate all the dialogue in this thread about exposure control and display , but since it will only be used as a third camera , or for casual use if out hiking etc , then this won't matter . Both the V1 and Z7 display all parameters on their LCD displays , and the controls on the Z7 are especially nice ; I can even mount the Canon and Fuji lenses from my JVC onto it and have 'real' focus , zoom and iris rings , but the supplied Zeiss lens just works so nicely . I can also use my Manfrotto pan bar remote with the Z7 , as I have done with the V1 and the VX1000 before it , although I have a Canon zoom demand which I've used for years with my larger cameras .

As I was reading the thread , and all the discussion about aperture controls and alternatives , I don't think the V1 existed in 2006 , but it is quite compact , maybe a bit bigger than the A1 - I shall see when I get it . Taking size aside , and bearing in mind the €2700 cost of the A1 , I can't help wondering what a GY-HD100 series camcorder would have cost back then ? I'm sure it would have been more , but how much more ? Although very much a 'prosumer' product , it was very much engineered to be a compact camera for people used to using professional ENG type cameras , and possibly unique at the time ; the only let down being it was 'only' 720p rather than 1080i as the Sonys and Canons of the time were . I still like my GY-HD251 and can't bring myself to part with it .

I can fully appreciate the comments about aperture and shutter speed , having done photography as a hobby ( never had any formal training but I learned a lot in the camera club I went to as a boy ) before I ever shot even 8mm cine , and having had many 35mm SLRs , as well as medium format both TLR and SLR , then both APSC and 35mm DSLRs , I can also appreciate how much the sensor size influences the way the lens parameters affect DOF . I have four digital still cameras with the capability to shoot video , yet I very rarely ever do so . The main exception being my little Canon Powershot G11 , and that is only because it as my 'always with me' camera , just as my old Rollei 35S was back in the film days ; so the Canon gets used to photograph things or film occurrences that I just happen across . My three Pentax cameras K-01 , K-3 and K-1 are just used for photography , although the first , being a mirrorless camera just somewhat larger than the Canon , and with a larger sensor , is the one I tend to take on family outings , or to places where carrying a large SLR would be too conspicuous , so again it might be used to shoot the odd video clip .

I have almost come round in a circle since I got a Bolex H16 REX4 cine camera a couple of years ago , but have never yet got around to shooting any film on it ; it is a lovely thing with fully manual controls , variable frame rates ( which must also influence shutter speed ) , a fade/dissolve gadget that closes down or opens up the shutter angle and of course fully manual focus and aperture controls on the lenses , besides the three small primes I got with it , there is also a large zoom lens , which will no doubt be optically inferior , but perhaps much more convenient in use . I also have a couple of period Weston Cine meters , as well as my several Weston exposure meters for still photography , although I only use my Master V or Euro Master when shooting stills on my Bronica , which I don't often do these days . At some point , after I retire , I will get some film and begin to learn to use the camera .

The main reason I do not use still cameras to shoot video is that is just not what they were designed to do ; the form factor is all wrong , the controls are all wrong , they don't have proper audio inputs or controls - yet you see these people with Heath-Robinson cages and all sorts of contraptions bolted on to the point that they probably spent more than a proper digital cine camera would've cost , and they still struggle to carry and operate them . Many still cameras also have serious restrictions resulting from memory card storage , or sensors overheating and shutting down after so many minutes ( and not so very many minutes ) of operation , because they were just not designed for that purpose . When I see people trying to shoot video with still cameras , I just get a sense that they are making a virtue out of awkwardness !

So , it has been 18 or 19 years since this thread started , and 15 years since the last comments ; I wonder if any of the original posters will see this , and perhaps even reply ?