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Old November 9th, 2005, 07:03 AM   #16
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Let me rephrase, "Crazy glue was used to apply a strip of velcro on the rim of a 72mm UV filter." :-)
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Old November 10th, 2005, 12:06 PM   #17
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Out of interest, does a UV filter help the image in any way? I do like the idea of some glass to protect the (expensive) WA adaptor
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Old November 10th, 2005, 12:28 PM   #18
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They say it does in some conditions, but I didn't notice it at all when I used one on my GS400 and it more like messed up the video, because when powerful light like sun entered the lens from appropriate angle, the picture got a big reflection of the UV filter. I'm now trying to skip the filter with my VX2100 and am using it only in conditions where the lens could get dirty for some reason. Instead I apply lens cap whenever I don't film.
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Old November 10th, 2005, 08:44 PM   #19
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Old November 16th, 2005, 11:04 AM   #20
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Alex - I'll say it again - a 72 mm filter costing 11 won't be coated at all, believe me. You go to your Panasonic shop and hand over 1200 for your new cam. The salesman smiles and tells you matter of factly that the front element of this fine 12x zoom lens is completely uncoated. How do you feel now? Would you still buy this model when the fully multi-coated version cost just 13 more? No you would not, and for very good reason.

I have a test I show people. I have two VX2ks. One has an uncoated UV and the other has a Hoya S-HMC UV. In less than 3 minutes I would have you skimming your 11 UV out over the lake, and you'd be smiling as you did it.

Ignore the UV side of things as all glass absorbs UV. The mechanical insurance protection offered by another slab of glass in front of the lens has to be weighed against the disadvantage of adding two more (dust-attracting) surfaces and the fact that converter lenses require you to take the filter off. Don't filter the front of the Raynox - the threads are there for attaching a hood. The massive DOF means however clean your filter, it's never clean enough.

Use the aspect ratio hood that came with your cam and dispense with the filter. This is my recommendation.

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Old November 16th, 2005, 11:18 AM   #21
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Thanks for the reply, Tom, and sorry to be dense, but I don't understand what you are advocating!

What is the purpose of coating?

BTW - I didn't get any hood with my cam, and I'm mostly worried about a hood for WA adaptor use.
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Old November 16th, 2005, 02:02 PM   #22
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You're not dense Alex, you're learning. Nothing wrong with being a student, and the brightest ones are the ones who ask all the questions.

Lenses are coated to increase the amount of light that is passed through the glass. There's also coatings to harden the surface of plastic elements, but we'll ignore those.

If you take a sheet of ordinary glass and shine a light at it, about 8% gets reflected back and doesn't pass through. This 8% comes off the front surface (entry) of the glass as well as the second (exit) surface. If lenses are coated - or better yet multi-coated, this reflection is reduced to about 0.5%, meaning that now 99.5% of the light gets through. The very best coatings (Zeiss T*) pass 99.9% of the light.

We're not overly concerned with losing 8% of the light - it's almost impossible to spot in an A/B test. But your average 12x zoom will have 13 or so elements making up the zoom, and you can imagine what would happen if each element reflected back 8% of the light that struck it. If the windows of your house comprised 13 panes of glass the outside world would be take on a nasty dim green colour.

The problem with uncoated optics is the reflection causes the light to 'bounce around' inside the lens cylinder, and this ends up washing over the image and causing what's known as veiling flare. The very best coatings are delicate, so spectacle wearers have to settle for 2nd best just to allow them to survive without scratching.

Do get a hood for your cam, and especially for the w'angle Raynox. That lens (to save money) only has a single coating, and a hood is a real necessity I find.

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Old November 17th, 2005, 03:35 AM   #23
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Thanks for that, Tom.

I presume that what you've left unsaid (as an exercise to the reader!) is that some of the problems of lack of coating can be significantly reduced through use of a lens hood.
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Old November 17th, 2005, 03:52 AM   #24
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Perfectly correct, star pupil.

What you want to avoid is non image-forming light hitting the front element. Once it hits it gets ducted into the lens, bouncing around and degrading your image. Sometimes this can be used to effect, and Photoshop, PSP etc include this 'failure' filter simply because modern coatings are so good.

So first off, ensure to the best of your ability that this doesn't happen. Use a hood (aspect ratio shadowed ones are best, petal hoods are good, cylindrical ones are better than nothing as is your hand held up, or ensuring the front element is held in a tree's shadow or something).

It takes but a few extra seconds to look down at your shadow when shooting into the light. You might only have to move a couple of feet to shadow the front element, and look - much better image quality at a stroke. Not only that but hoods that come fitted to zooms are only efficient at the wide-angle end. They're horribly inefficient at telephoto.

Pop over to www.cavision.com. They do a few good hoods and flags and matt boxes.

And lastly, remember this. Any imperfection in the lens coating will negate its effect almost entirely. One single fingerprint (greasy by its very nature) will allow light to enter the lens element, even if it's T* coated.

And point two. A lens hood is the cheapest, lightest, simplest way to improve your picture quality. The next accessory up - the tripod - is many times dearer.

tom.
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Old November 17th, 2005, 10:33 AM   #25
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Alex, the Raynox .66's 72mm face just loves to introduce flare of several types into your images...some of it not obvious like the veiling Tom refers to. In my opinion, this lens absolutely requires the largest hood you can find or make. If you look at my design you'll see that it is fairly large, and it observes a 16:9 ratio of width:height. Quite frankly, a french flag should be added on. Don't bother with a screw on plastic hood. None of them will be big enough to be worth buying.

I regulary use a 72mm Tiffen .6ND, and a Tiffen 72mm circular polarizer on this lens. The filters were not cheap! You do need to keep things clean, but getting the GS400 into the F5 range pays off when you examine your images. If you are using auto mode in bright conditions, the camera will peak at F16 and 1/60s so you must either add the filters, or switch to manual and crank your shutter speed. If you check out the pics and clip here you will see the lens flare fire up as the crane'd GS400 with .66 WA turns toward the sun, even with my large hood attached.
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Old November 18th, 2005, 10:12 AM   #26
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OK, so what's your latest mad invention?!!!

I see that was back in January - are there any other new clips around showing use of the crane?
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Old November 18th, 2005, 10:42 AM   #27
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Chuckles quietly to himself ... Here's the latest.
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Old November 18th, 2005, 11:17 AM   #28
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Nice rig Dennis, and good to see you're using a 16:9 hood - and I presume you're then shooting 16:9?

Just a reminder that your Panasonic may well indicate f/16 while recording and on replay later, but this is just an extrapolation of the figures of course. The automatic internal ND filters won't allow apertures as small as this as the diffraction losses would be quite unacceptable in a camcorder with such tiny chips. It's much more likely that you're shooting at f/4 or f/4.8, and the internal ND is soaking 4 stops of light.

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Old November 18th, 2005, 04:18 PM   #29
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Yep, pretty much 100% 16:9. I've done a fair bit of testing on the cam in auto and manual mode, and judging from the blown out footage in bright snow, it just maxes at F16 then overexposes in auto mode. Although the internal ND filters have been documented in Panasonic's PV953, I've yet to see anything in official print on the GS400...although it is assumed they are there. Have you found anything on this?

I did some carefull analysis on the GS400 at F8 vs F16 (using a .6ND and CP) and did observe noticeable image degradation at F16. Ever since then I've tried pretty hard to stay in the F5 to F8 range.
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Old November 18th, 2005, 05:29 PM   #30
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Manufacturers are very coy about their automatic internal ND filtration. My MX300 has a ND attached to the lower aperture blade and at small apertures this comes on axis automatically. Stupid thing is that at full telephoto there's ALWAYS ND in place, so making the camera even worse in low light if you use any tele at all. No wonder they keep quiet.

I tested the Sony PDX10 for Computer Video magazine here in the UK, and found (completely undocumented) that it contained 3 ND filters. These are slotted into the light path one after another as soon as the aperture blades hit f/4.8. But the PDX10 doesn't give aperture readouts (and this is supposed to be a pro camera?) and on replay the display figures are just wrong. This is a polite way of saying Sony lies to us.

The MX350 and 500 both give made-up figures for aperture values - going as far as f22. Nonsense of course, but the punters feel happier to read figures on rec and replay. I'm betting the GS400 uses exactly the same technology, but I've yet to see it for myself. I write not a word till I've seen it for myself.

Sony's TRV900 insisted you inserted the ND manually, but folk would often forget and the camera would then have to up the shutter speed to compensate. But even so, using f/9.5 (when the higher shutter speeds were brought into play) would still give soft images at wide-angle. This is because very short focal lengths are much more susceptible to diffraction losses.

So yes, do try and shoot at f/4 or wider with a 1/5" chipped camcorder, and certainly with a 1/6" camcorder consider f/4 as the smallest aperture you should ever use.

Not too that the C-Mos chips of Sony's new A1 don't require internal NDs.

tom.
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