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-   Sony TRV950 / PDX10 Companion (https://www.dvinfo.net/forum/sony-trv950-pdx10-companion/)
-   -   PDX10, smallest aperture is F4? (https://www.dvinfo.net/forum/sony-trv950-pdx10-companion/25607-pdx10-smallest-aperture-f4.html)

Love Mov May 5th, 2004 11:20 PM

PDX10, smallest aperture is F4?
Did some test in manual mode tdoay. The exposure has 24 steps, step 0 is 'close', step 13 to step 24 from F4 to F1.2(maybe F1.6, forget) and gain from 3db up to 18db. Now, from step 1to step 12, it's always F4...
Is this right? What was wrong? I remeber read somewhere, people have F9.3 or something...

Boyd Ostroff May 6th, 2004 08:17 AM

How did you do these tests? What was the shutter speed? Are you basing the results on the data code that's recorded on tape? The PDX-10 clearly gives some erroneous results that way. For example, when you're at maximum zoom it will sill report f 1.6 apertures even though that is physically impossible.

However, you could be right because we now know that there is an internal ND filter wheel that pops into the optical path as you turn the exposure wheel. The idea is evidently to force exposure to stay in that range around f4 in order to coax the best resolution from the lens. So instead of making the iris smaller the camera is putting in denser ND filters. Sony has never documented this.

Look back a ways in this group for lots of discussion on this topic.

Love Mov May 6th, 2004 06:23 PM

Just did some search, you're right, tons of simliar discussion here, very informative. Seems sony screw the data display, have to live with it...thanks.

Tom Hardwick May 7th, 2004 02:31 PM

Sony are not the only ones to be economical with the truth when the Display button is hit. The Pansaonic MX300/350 and 500 all use internal ND filtration instead of smaller apertures, yet all will happily report that you took this shot at f16 (say). Canon are on the same boat, and their MVX3i also makes up aperture figures that it thinks you'll believe.

Of course you can get the PDX10 to shoot at smaller apertures than f4.8. You have to disable the auto shutter and point the camera at a bright reflection of a lake or something. If you do this you'll see why the auto in-built NDs are so important with such tiny chips.


Love Mov May 7th, 2004 04:52 PM

Actually, all my testing is concerning that the build in ND filter is not that great. The ND is important, and sometimes a must have, but will be an external quality brand one is much better? If so, this explains why cloudy shot (all internal ND is off) is better than sunny day (some or even all ND is on).
Even the internal ND is good enough, there are situations that 2 or more (some said buid in ND is 3) ND is in the light path, this is certainly not a good idea PQ wise...

Tom Hardwick May 7th, 2004 11:57 PM

It's a good idea (movie) picture quality wise if the alternative is faster shutter speeds or smaller apertures. But I agree with you in that when all three NDs are in place then that's three extra elements in the lens line-up, as as far as I can see none of the NDs are coated, so they will add small amounts of flare and lose a tiny bit of sharpness.

But it's interesting to read your findings that you consider the picture quality better without the NDs in place. Of course this is theoretically so, so you might just have one ND with a crease or a smudge on it. Also note that the PDX10s filters slide gradually into place, so that at any given time you could be shooting through the cut edge of the filter. This is not nice, but is done to ensure that the aperture doesn't go smaller than f4.8. You might think that shooting through half an ND in this way might give you a 'graduated filter effect' on screen but this is not the case due to the filter's position within the lens element line up.

I've read the same on the VX2k forum where one person found that the two (manually operated) NDs on that cam diffused the image somewhat. On this cam you never shoot with 'half a filter' though. It's easy to test out of course. Buy yourself an expensive, coated, 37mm Hoya three stop ND. Firm tripod, test target. Applying the Hoya should cancel out one or two on the in-built NDs. See any difference?


Boyd Ostroff May 9th, 2004 01:07 PM

You still may want to use an external ND filter in order to shoot wide open under bright conditions where you want shallow depth of field.

Tom Hardwick May 10th, 2004 01:02 AM

Quite correct Boyd. Much better to force maximum aperture with an extra ND than it is to up the shutter speed. My big gripe though is not being informed when maximum aperture has been reached and gain-up takes hold. Why on Earth Sony didn't put a small marker line on the exposure bar to tell when this takes place I'll never know. After all they managed it with the changeover from optical to digital zoom.

My guess is they couldn't mark this line, and that the position varies depending on whether you're in auto or manual, different w/bal or program settings. Interestingly the TRV 900/PD100 had a -3dB setting on the gain-up, to lower the noise floor for all your shots that didn't require max aperture abd beyond. This is another loss in the changeover to the 950/X10, although the newer chips are inherrently less noisy anyway.


Boyd Ostroff May 10th, 2004 06:57 AM

Well when I'm shooting under low light conditions I just assume that the last 4 clicks are +3dB, +6dB, +12dB and +18dB.

Tom Hardwick May 10th, 2004 07:18 AM

Problem is that each click is half a stop Boyd, so you have to go up to +18, then back through 15, 12, 9, 6, 3, 0 to find maximum aperture. This is time consuming and filldy.

Ignacio Rodriguez May 12th, 2004 12:10 AM

> But I agree with you in that when all three NDs
> are in place then that's three extra elements in the lens line-up

Really? This is very alarming! I would have thought that there is a four position wheel with a non-attenuating piece of glass and three progressively 'darker' filters, so that internal focusing is not affected.

Has anybody actually dissasembled the camera and seen the way the filters are placed? Are they lined up for stacking or are they set up as I suggest?

BTW., there is a little something, possibly a particle of dust, just behind the front element of my camera's lens. It's effect sometimes shows up in my footage #@&%$/ I have been thinking about opening it up and using a can of air to try to blow it away... any opinions?

Tom Hardwick May 12th, 2004 01:09 AM

I haven't opened up a PDX10, I've simply used a focused maglight to look down into that lens. You can turn the exposure wheel and see the little NDs bumping into place, one after another. Fine control of the auto exposure (if f4,77 is required for instance) is done by the ND moving smoothly into the lightpath, but in the manual exposure mode this is not possible, and half stop jumps in the filter positions are made. You're often shooting through the 'edge' of a (wildly out of focus) ND filter.

I too was surprised that a single 'graduated' ND filter was not used by Sony. so that the more it moved into position, the more light it absorbed. This would have reduced the losses associated with adding extra elements (and three NDs = 6 extra reflecting surfaces). There must be a good reason for going the seperate filter route, and I suspect it's cost. Focusing is not affected simply because the automation is looking for the greatest contrast in the subject and not interested in the optical lineup.

If you point the camera at a plain white/blue sky the auto focus will hunt, sometimes (at small apertures and very wide angles) it will lock onto the dust on a UV filter for instance. It's simply found the greatest contrast out there.

Your foreign body sounds disturbing Ignacio. Can you shake it so that it drops out of the line of fire or is it 'stuck' to the glass element? Opening it up will not be something I'd recommend as my guess is (having taken camcorders apart) that the lens and chip-block is a sealed, bought-in assembly. No user adjustable parts inside, that sort of thing.


Ignacio Rodriguez May 12th, 2004 09:13 AM

> Your foreign body sounds disturbing Ignacio.
> Can you shake it so that it drops out of the line
> of fire or is it 'stuck'

Shaking does not move it. Actually now I see three particles :-(

Ignacio Rodriguez May 13th, 2004 09:40 PM

> Focusing is not affected simply because the
> automation is looking for the greatest contrast
> in the subject and not interested in the optical lineup.

Hmm yes, but this would not explain why focus is not affected in manual focusing mode.

Tom, the "auto shutter" menu setting turns off the auto ND thing but only in automatic mode, right? So there is no way in manual mode to disable the internal ND filters aside from adding an external ND, am I right?

Tom Hardwick May 19th, 2004 01:58 PM

Let's think this through.
Turning the auto shutter off in the menu stops the camera upping the shutter speed automatically, without telling you what it's choosing. When the light levels increase to the point where all three NDs are in place and the camera wants to stop down some more, normally this is the point where the shutter speeds start to rise. If you've disabled this function (good for movies), the camera has no alternative but to choose smaller apertures than the f4.8 that it normally defaults to.

"So there is no way in manual mode to disable the internal ND filters aside from adding an external ND, am I right?"

Correct Ignacio. There's no way of avoiding the internal NDs. If you use an external ND you're just delaying the onset of the internal ND utilisation. If it gets bright enough they'll be called into play - auto or manual, it matters not.


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