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Sony TRV950 / PDX10 Companion
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Old October 13th, 2003, 07:52 PM   #1
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Tom Hardwick > Paradox 10 :)

Tom,

Having read your thread on this camera, I have conducted tests and have come to some slightly different conclusions or at least conclusions which tally with my observations and wish to confer with you to see why they should be different, unless of course my cams are different.

ND filtration

When I got my cams over a year ago I too looked down the lens with a 6 inch spot focussed Maglite and found that the iris responded to the light as normal. So tonight, I repeated the test to try to understand what you have found.


AUTO LOCK mode

In this mode with zoom set to telephoto for ease of viewing and with a tape running in record and shining the above Maglite down the lens, I see the two bladed aperture converging until 1mm apart. Playing back the tape with data code display on, I see f numbers responding to the light f4,5.6,6.8,8,11,16 until f19 appears corresponding to the 1mm separation seen above. So this is basically the same as one year ago. I also see something move across the light path behind the iris. ..

AUTO LOCK RELEASE mode

In this mode repeating the above test, I see the aperture close down to f3.4. At an exposure reading of f4 centre scale, I see the aperture fixed at f3.4 and an ND move a third way into the light path. At further levels I see up to 3 NDs move across the light path in thirds which exactly corresponds to the 24 exposure clicks from f4 to f32 at which the aperture closes completely. Playing back the tape the data code does not go beyong f3.4

HOLD mode

The behavior is essentially the same as AUTO LOCK RELEASE mode in respect of indicated aperture being no greater than f3.4


CONCLUSION

Firstly I am gobsmacked to learn that the exposure operation of this cam is fundamentally different between AUTO LOCK and AUTO LOCK RELEASE/HOLD modes. However having accepted that it is, I conclude that this is a firmware bug for the following reason.

To my mind and logically, the introduction of ND filtration, whilst a good thing in certain respects, should be reserved only for AUTO LOCK mode to 'protect' inexperienced users from diffraction effects. In AUTO LOCK RELEASE/HOLD mode full control of the aperture through its full range should be permissable without the ND.

It would appear that the SONY engineers have reverse-wired this feature (auto versus manual) in the firmware since the aperture fully operates but only in AUTO LOCK mode.

Owners should complain and demand a firmware upgrade FOC/ASAP.
----------------------------

DATA CODE readout

I conclude the readout is reporting aperture size and not exposure which tallies with all the above observations and also in the telephoto/open aperture setting of f1.6

The spec value of f2.8 at full telephoto is the 'effective' aperture which is wholly due to the small object lens (25mm) appearing to get smaller (to f2.8) as the composite lens block moves back toward the CCD end of the barrel. The real aperture doesnt close down from f1.6 to f2.8

Here again a firmware bug - DATA CODE should report exposure and not aperture size.
-----------------------------

I would appreciate your comments
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Old October 14th, 2003, 01:40 PM   #2
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Thank you for your scientific approach John, and for your input.
Firstly mine is the PDX10P (P for PAL). Is yours?

My PD is indeed different from yours, and this greatly surprises me. My serial Nr is 1211***. In the Auto Lock telephoto mode mine goes from full aperture of f2.8 to f4.8. The blades stop closing at this point and more light just brings on the ND filter. More light yet and the second and then the third NDs slide gently into place.

AUTO LOCK RELEASE mode is exactly the same - as you would expect. Your data code does not go beyong f3.4 but mine goes to f4.8. More strange things, huh? HOLD mode simply holds onto this mode, so no changes or surprises there.

You say in your conclusions: In AUTO LOCK RELEASE/HOLD mode full control of the aperture through its full range should be permissable without the ND. .. and I can only agree with you 100%. If any of my other cameras refused to let me access 4 stops for DOF control I'd be cross. The PD100 was fine in this respect, and that camera allowed you to shoot in either shutter or aperture priority mode (AEA). Naturally the PDX won't allow this mode as you have so few apertures to access it hardly seems worth while including such a program.

You're correct in that the readout is reporting aperture size and not exposure. But does your Data readout also make silly claims as to maximum apertures at full tele that the camera quite obviously doesn't have? Mine regularily says I shot at full tele using f1.6, f2 and f2.5 - all nonsense of course.

You say: The real aperture doesn't close down from f1.6 to f2.8, but indeed it does John, as looking down the lens will show you. As you move away from full wide angle the two aperture blades never fully retract into the diaphragm housing, so effectively cutting the maximum aperture that's available.

You say: 'DATA CODE should report exposure and not aperture size' but I disagree. Data should display exactly what each frame was shot at - aperture and shutter speed - to the nearest half stop.

OK. Tech time over. Because of the difraction losses that people could experience with the PD100 the new designers have deemed it necessary to bar us from using anything smaller than f4.8. As such the pictures are pristine, but I'd still prefer manual control of my NDs, thank you very much. The *only* way I can access the smaller apertures is to film in light bright enough to need a *forth* ND filter - then the aperture blades will continue down to closed. The Display will indicate ..f22, f28, close.

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Old October 14th, 2003, 02:36 PM   #3
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yes

mine is several k older than yours, I put this down to differences in manufacture although the AUTO LOCK mode difference is surprising

it appears that Sony engineers have decided to give us exposure operation more akin to a mirror lens use in AUTO LOCK RELEASE.

besides shining maglights down the lens, I took a series of photos from the office window today to see what penalties if any, in telephoto depth of field, do these NDs have.

I am relieved to say that even though the picture below was shot at F19 with an indicated aperture of F3.4 the depth of field is similar to a 'real' small aperture

http://img.villagephotos.com/p/2003-8/348236/Untitle888d.jpg

the tree tops and the chimney are about 1 mile apart with the tree tops about 60 yards from the camera (spot focus to the chimney) - any blurrines in the rest of the image is due to motion

Seems like those Sony people have figured that the confines of the DV25 format make anything below F3.4 (in my case) redundant and you only need 'real' aperture below this.


Having reviewed this with real images - I am happer than before and can travel lighter without packing ND except for 1.6 type shots.



PS have you noticed the bug that in AE portrait mode the lens still stops down instead of holding at F1.6?
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Old October 16th, 2003, 05:37 AM   #4
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The portrait mode on my PDX10 won't allow a shutter speed any higher than 1/425 th sec. It will vary the aperture from f1.6 to f4 and if it gets brighter it simply introduces more and more ND. It won't up the shutter speed for good reason - any speeds higher than this cause vast CCD flare - sometimes obsuring the whole frame with splodges of red and green. Even at 1/425th the CCD flare is obvious in quite normal high contrast scenes (where the sky meets the horizon for example).

John - can you explain your line: the picture below was shot at F19 with an indicated aperture of F3.4 . It's much more likely to be the latter than the former.

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Old October 16th, 2003, 01:43 PM   #5
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the picture was taken in AUTO LOCK RELEASE mode, full telephoto, 4:3 for maximum magnification, no custom preset.

The reason for this is that when shutter speed and exposure are not shown in the LCD it is effectively AUTO LOCK mode, however by pressing the exposure button the camera will tell you what exposure is being used. In this case the scale indicated three clicks from the left-most position which is F19 (F4 is dead centre - at least in wide setting!). Playing back the tape at the exact spot of the moving ship, the DATA code reads F3.4

Clearly everything is in focus (within the limitations of handheld using the window sill as a brace) so the photographic performance from DOF standpoint does not seem to be compromised

taking into the discussion above where the DATA code reads F1.6 when it should read F2.8 then perhaps this F3.4 for the picture is really F5.6 - but then again all this is really trashing my head!

-------

Tom, I am more then curious about the apparent differences between our cams, can you please try this.... Shine the mag in full telephoto in manual mode (ALR) at an exposure setting of one click left of centre. I see the 'mimimum' aperture (which is indicated as F3.4 DATA code) with the first ND exactly bisecting the diamond formed by the blades. If yours is different maybe the chip sensitivities are different...
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Old October 16th, 2003, 02:05 PM   #6
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Ah, now I see what you mean when you say f19. In actual fact it's f3.4 (or more probably f4) with all three NDs in place, giving an effective f19 but with none of the diffraction drawbacks. The DOF will be the same as if you shot at f4 with no NDs in place of course. NDs don't affect DOF.

'then perhaps this F3.4 for the picture is really F5.6 - but then again all this is really trashing my head!'

Don't let it. When you look down into your lens with the zoom at full tele, use the exposure wheel to open the diaphragm blades fully. This is f2.8. next stop: f3.4, next stop f4. The blades on my X10 don't close further than this sweet spot; from here on in the NDs start arriving in droves.

OK, to your test. Dead centre on the silly bar chart is directly under the "i" of "min", and on my cam that's the smallest aperture you can shoot at. In fact in this position the aperture has closed to it's smallest value (f4) and the first ND has just started to rise up. Does that help you?

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Old October 16th, 2003, 02:20 PM   #7
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yes at the dead centre scale the first ND is just clipping the bottom of the diamond, the next click to the left bisects the diamond

PS. the position of the i in min will move at low battery charge
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Old October 16th, 2003, 02:40 PM   #8
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Yes, thought it might! What a stupid, unscientific, amateurish and feeble exposure display this is. It's reall 1995 Video8 stuff. This camera is aimed at aspiring professionals, is it not? Yet the bar doesn't tell you when you reach maximum aperture, when gain-up starts its degredation or when the NDs start arriving.

I love shooting faces at weddings, so I need to shoot at full tele and maximum aperture to minimise DOF. I need to keep away from gain up because of DVD encoding, so what do I do with this camera?

Sorry if you others out there find this a bit tedious, but I do love digging and getting the very best out of any camera that passes my way.

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Old October 16th, 2003, 02:56 PM   #9
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he he


thats the paradox, by trying to find out how this thing works it is teaching us more about something we thought we already knew.


for example I have calculated the ND strengths as 9db, 18db and 27 db

now at that position I mentioned above (halfdiamond) if the ND1 was a solid opaque it would mean a whole stop light reduction from minimum aperture since the light is cut by 50% but what is the exposure at one half clear and one half ND1 9db cut?? ---- I think Ive just blown a fuse :)
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Old October 16th, 2003, 03:19 PM   #10
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Because the NDs are used to infinitely vary the exposure (between the limits), the ND's have to slide in and out of the light path. In the auto mode they're constantly on the move of course, and tape is being exposed while the NDs are moving.

This is not good photographic practice because of the flare caused by reflections off the hard cut edges of the gelatin filters when they're only part way into place. That's why on the TRV900 and the VX2k the ND's 'snap' into place, and why photographers dont 'half fit' NDs in front of their lenses.

Another thing. Although the NDs are hugely out of focus being placed at the diaphragm position, they still reduce the exposure unevenly across the frame. But my guess is that's the least of Sony's worries.

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Old October 16th, 2003, 04:22 PM   #11
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Tom

your last reply would seem to suggest for the reasons you state that external use of ND would be preferable? In which case we have gone full circle, paradoxically :(
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Old October 17th, 2003, 01:43 PM   #12
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Oh it would certainly be photographically preferable. But think of the hassle factor. Think of the diffraction losses.
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