How could I know at which f-stop The HDR-A1 is shooting? - Page 2 at DVinfo.net

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Sony HVR-A1 and HDR-HC Series
Sony's latest single-CMOS additions to their HDV camcorder line.


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Old February 14th, 2006, 07:47 PM   #16
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Agree with Tom.

I have HC1000 which is essenitally the non-pro version of the PDX10, but has essentially the same mechanicals minus a few features like XLR etc.
My cam's reported aperture really doesn't vary that much. in good light it'll shoot at f3.4 or f4 or f4.5. Low light obviously it drops down to f1.8 max.

But i can't recall it ever *reporting* (via data code) an aperture of smaller than f4.5 -ish. Also you can *hear* it moving ND filters into or out of the optical path on power-up. At least i *think* that's what the 'clunking' noise is on power-up. Power-up with lens cap on, obviously it's going to move all ND filters out of the way, and go max.ap, max.gain due to pitch blackness.
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Old February 14th, 2006, 09:57 PM   #17
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Quote:
Originally Posted by Vincent Sanchis
However I am a bit concerned about its capabilities, due to my background as cinematographer.

... or to be more precised there is no information on the f-stop the camera is shooting.
I know why you must have control of the F-stop with SOME film cameras, but why would you need it with a video camera?

What are you trying to accomplish?
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Old February 15th, 2006, 01:59 AM   #18
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Stu, the HC1000 was the next model on from the TRV950, which itself was the PDX10. So your HC1000 (good though it is in auto) was a dumbded down TRV950.

I suspect the clunking you hear at switch-on is the OIS elements being pulled into position electromagnetically, not the internal ND filters leaping about. They are tiny slivers of gelatin, very small indeed and very light.

Steve - you would want control over the iris primarily for depth of field reasons. On a camera such as the VX2100 you can slot either or both of the NDs into the light path, each one altering the taking aperture, each one varying the amount of background bluring.

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Old February 15th, 2006, 02:17 AM   #19
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Well, I see I'm alone against 'Sony's way' to do marketing.
I know that for a bit more money I can get a FX1 (with many 'compromises' as well, like not having XLR and others), but right now the stronger point of the A1 is it's small size (very handy for shooting when you don't want to be noticed as a 'pro'). And I will pay even more money for the A1 if it will give me the information on f-stop.
Why am I so desperate asking to have the ability to set f-stop? Because I have been a photographer for many years, and I think like a DOP (depth of field is an important point as Tom says). I like to shoot manually unless it's imposible for any reason. If I have to shoot I use to take always my lightmeter. Like one book says 'every frame is a Rembrandt'. So I am one of this kind of cinematographer.
I start my jump to HDV with the A1 to make this camera the 'B camera' (if I like its footage and workflow of the 1080i format, and then buying a Z1) and for shooting documentaries, but right now it's the 'A camera' and I would like to test the HDV format doing some shortfilms with my friends, and at least for me it's imposssible to shoot a decent shorfilm without the f-stop information.

Besides I'm not sure that 1080i and HDV is the future, it's just a transition format. I think the future is progressive and tapeless.

Thanks for all your replies.
This thread is being very interesting with all your posts.
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Old February 15th, 2006, 03:12 AM   #20
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You're right Vincent. HDV is a transition format.

Some thoughts on the Panasonic HVX200, the 'DVX100 on P2 steroids'.
Remember this is genuine HD, not HDV.
The problem I see is that P2 doesn't actually offer a solution to any problem. The fact it is non linear is great. But it replaces the old problems of tape with new problems of its own. That being the risky business of having to trust that you can offload your footage every 18 minutes and that you don't have a hard drive crash or transfer error (as some people have had) before wiping the card to carry on shooting. You have to carry a laptop as well, of course.

As for the price, Top-Teks told me that they expected to be selling in (from
March) at £3,500+VAT, with 4GB cards going out for £430+VAT. Here's the
dollar prices:
4GB P2 High Performance Card $650.00
8GB P2 High Performance Card $1,400.00

That's eye-watering, even admitting their relevance in the dusty, bumpy
field.

The HVX200 is a bold step in the inevitable direction, but possibly a year
early. It makes sense for a new start-up, but much less so for a conversion
from tape. The next year should provide the experimental evidence either
way. My view is that P2 is a step along the inevitable road away from tape.

tom.
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Old February 15th, 2006, 12:11 PM   #21
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One little bit of info about A1 is that i've heard from several different places now that a certain George Lucas bought a truck-load of Sony A1's for use by him and his company. So i guess he copes without knowing too well what the aperture is !! (Unless Sony make a 'George Lucas' special version...).

Vincent - i do agree with you on the aperture reporting (well....non-reporting). I can see Sony leaving it off the consumer HC1 but why leave it off the A1. So i empathise with you there.

I suppose as Tom said, they KNEW they'd sell bucketloads anyway as there's just no current competition for a small light HDV camera for small-ish money.
I think their Ace of Trumps is there sensor-building expertise - this is the heart of a cam and allows them to get these sort of cams out before the opposition. Sony sells sensors to quite a lot of other companies. (like Minolta for example.)

ps. RIP Minolta cameras. :-/
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Old February 15th, 2006, 01:25 PM   #22
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Quote:
Originally Posted by Tom Hardwick
Some thoughts on the Panasonic HVX200, the 'DVX100 on P2 steroids'.
Remember this is genuine HD, not HDV.
I'm not sure that's an accurate statement - it implies that HDV isn't genuine HD and that DVCProHD somehow is - but both make compromises which put their specs at less than "true" HD. DVCProHD may have more color information and less compression, but it also has even less pixels than HDV. In fact, when talking about 720p HDV could easily be considered "more" genuine HD because it has the full resolution of the HD spec - 1280x720 - whereas DVCProHD is only 960x720.

This is not to say the HVX200 isn't a better camera than some HDV cameras, but neither one is necessarily more or less a genuine HD format - they simply make different compromises which reflect the varying needs of end users.
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Old February 15th, 2006, 06:03 PM   #23
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Quote:
Originally Posted by Tom Hardwick
Steve -- you would want control over the iris primarily for depth of field reasons.
If one had a DOF chart for the lens -- one could set a specific aperature -- but there is no chart. This is not a cine lens.

So one simply opens the iris wide which you can clearly see two ways: you can see the INDICATOR MOVE and you can actually see what's in focus -- and what's not -- in the viewfinder.

So are there are any other reasons why one would need to know the specific iris value?
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Old February 16th, 2006, 02:22 AM   #24
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You're right Steve - we all have wysiwyg viewfinders. They may be pretty small and of low resolution, but they do show us the shot at taking aperture, white balance, shutterspeed and gain settings. As such we do get to see the dof as we'll see it later, unlike with ciné lenses of old.

But as a photographer I do like to be in control, and by that I mean I like to know my settings. I might want to use max aperture and higher shutter speeds with absolutely no gain up. I might want to select f/4 so that I can pan in progressive scan and stitch the pictures together later without fear of vignetting giving the stitch away. I might well want to avoid f/8 and f/11 for the simple reason that diffraction means I lose sharpness.

And on the test bench for evaluating camera A against camera B it's invaluable to know exactly what's going on, even when the aperture and shutter speed readouts are only ever to the nearest half stop (which they are of course).

Cameras such as my three chip Panasonic fudge viewfinder information, telling me I'm shooting at f/16 when quite clearly I'm not. It may be an extrapolation of the f/4.5 + the internal ND, but I feel it's somewhat patronising and I'd really rather know the truth.

tom.

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Old February 16th, 2006, 03:20 AM   #25
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Quote:
Originally Posted by Tom Hardwick
I might want to use max aperture and higher shutter speeds with absolutely no gain up. I might want to select f/4 so that I can pan in progressive scan and stitch the pictures together later without fear of vignetting giving the stitch away. I might well want to avoid f/8 and f/11 for the simple reason that diffraction means I lose sharpness.
Your answers are all good ones, but I'm not sure they make sense given the way the A1/HC1 works. To prevent the shutter-speed from seeking it's own speed, you generally must lock it at 1/60th Sec. At 1/30th you'll have too much blur. At 1/120th you'll start getting strobing.

With video cameras, sensitivty varies because of gamma -- which you don't know and can't control -- so you cannot set the iris based upon a lightmeter reading.

In fact, because these cameras add/remove ND filters -- whose values you don't know -- as the AE system decides when and what, you really are NOT in control.

Moreover, the very limted iris range means you fundamentally only have about five exposure zones: GAIN-ON, OPEN, ALMOST OPEN, MIDDLE, and ALMOST CLOSED.

To avoid loss of image quality, avoid GAIN-ON and OPEN.

For minimum DOF, you need ALMOST OPEN.

Most of the time you want MIDDLE to avoid loss of image quality.

And, for maximum DOF you want ALMOST CLOSED.

Thus my question was a subtle way of saying the issue isn't the lack of visual F-stop indication, but that the lack of markings falls out of the way these cameras work.

Note, I'm not saying you can't use one of these camcorders. Only that you must translate your cine techniques to the camera's AE system. And, I think that is possible if you think in terms of ALMOST OPEN (F2>F4), MIDDLE (F5.6>F8), and ALMOST CLOSED (F11>F16).

My FX1/Z1 book covers much of this for the A1/HC1.

Other posts describe how you can mark the indicator.
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Old February 16th, 2006, 03:40 AM   #26
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Steve, you say: ''In fact, because these cameras add/remove ND filters -- whose values you don't know -- as the AE system decides when and what, you really are NOT in control.''

This is quite correct and CCD camcorders have been using internal (and undisclosed) ND filtratiuon for very many years as a solution to the 'tiny chip diffraction' problem. But I'm not convinced that the cmos chip used in the A1/HC1 uses any internal ND. Can you confirm or deny if internal ND is used on this model? I don't have one so am not in a position to find out.

No good asking Sony as the three internal NDs used in the PDX10 (to great effect I might add) were never mentioned anywhere, in any technical spec. Panasonic have been more open about it on the DVC30 however.

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Old February 16th, 2006, 05:25 AM   #27
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Originally Posted by Tom Hardwick
But I'm not convinced that the cmos chip used in the A1/HC1 uses any internal ND. Can you confirm or deny if internal ND is used on this model?
I can't prove it either. But folks have posted this -- and the limited iris range AND the fact you can lock shutter-speed sort of indicates that something must be done at very bright illumination levels to prevent over-exposure.
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Old February 16th, 2006, 10:56 AM   #28
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ND filters

i've *heard* that it is possible to see the ND filters move in and out by looking down the lens barrel. I suppose do it in dim light, and then shine a flashlight down the lens barrel and you can allegedly see the tiny ND filter swing into the optical path. only thing that may get in the way is the aperture leaves, but i don't know whether they're in-front of or behind the internal ND filters.

I know someone's done this and he said he can see the internal ND filters move about when he changes lighting levels.
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Old February 16th, 2006, 01:14 PM   #29
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Ok, I just checked my HC1 with a flashlight. The iris is wide open in the first 7 positions (starting at the far right of the onscreen exposure bar) of the exposure lever. From 8-12 the iris closes until it is about halfway closed (it's a 4 blade diamond shaped iris, by the way). From 13-19 it appears as if 2 ND filters slide in - each one stops at 4 different positions. From 20-23 the iris continues to close (with both ND's fully in place) and at 24 the iris closes completely.

This matches the results of the data code chart here: http://hdvforever.com/hdv/exposure/ and confirms in my mind that the theory there about mapping the bit values is incorrect. The NDs are used to allow the widest range of exposures at f.4 probably because that is the sharpest spot for this lens. R.P. Cuenco mentioned above that the service manual references 2 NDs so I think at this point we can consider it confirmed. I'll put together a new chart with the accurate f-stop and ND information for each position and post it up tomorrow.

Quote:
Originally Posted by Steve Mullen
I can't prove it either. But folks have posted this -- and the limited iris range AND the fact you can lock shutter-speed sort of indicates that something must be done at very bright illumination levels to prevent over-exposure.
Just to clarify though, if you lock shutter speed and exposure the ND's are not added automatically to prevent overexposure - the camera is perfectly happy letting you screw up your exposure completely if you wish, so you do have the ability to completely stop any automatic exposure. The NDs correspond to repeatable positions on the exposure bar.

Last edited by Evan Donn; February 16th, 2006 at 05:40 PM.
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Old February 16th, 2006, 07:17 PM   #30
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Just to clarify though, if you lock shutter speed and exposure the ND's are not added automatically to prevent overexposure - the camera is perfectly happy letting you screw up your exposure completely if you wish, so you do have the ability to completely stop any automatic exposure.
If you lock ONLY the shutter-speed -- do the ND filters continue to work?

I assume they do as part of the AE system.

+++++++

The iris is wide open in the first 7 positions (starting at the far right of the onscreen exposure bar) of the exposure lever.

Of these 7 positions -- how many are GAIN UP positions?

And what GAIN values do they represent?

Great job testing your camcorder!
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