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Old August 3rd, 2004, 02:34 AM   #16
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<<<-- Originally posted by Duncan Wilson : The technicalities of this are way beyond my knowledge, but it is worth noting that you can use non-Canon "EOS-fit" lenses with the EF adapter. I use Sigma lenses, and the XL1 does recognise these lenses. As has already been noted, this may indicate that the "fault" lies with P+S rather than the XL1.

On a different subject, could anybody tell me how "T" values relate to "f" stop values on still lenses. Is T2 the same as f2, and what does the "T" stand-for?

Cheers
Duncan -->>>

Hi Duncan
I'm definately no expert but as far as I am aware a T spot is esentially an F stop that has been calibrated for the lens. Because the lense glass absorbs some light the F stop values are slightly wrong. T stops are F stop measurements that have been adjusted to correct this. So a T stop would be an F stop with a perfectly transparent lense. I i'm trying to say they are like F stops but more accurate.

Anyone know if this is correct?

Brent
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Old August 3rd, 2004, 02:57 AM   #17
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T stops are light-transmission stops. They are a more accurate way to judge exposure.

F/stops are a mathematical derivation of the size of the lens opening in relation to the focal length of the lens, most useful for calculating depth of field, etc., but not as accurate for judging exposure as a T/stop.
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Old August 9th, 2004, 12:26 PM   #18
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The Canon XL2 and the Mini35 will indeed work just fine together. In fact, Canon had a Mini35 unit in their possession during the their design phase. That being said, what P+S Technick is working on now is a small adjustment to accommodate the thicker platform of the XL2.

This re-engineered section will be incorporated into future 400 series Mini35 units and will be available as an optional replacement kit for existing Mini35 units, 300 or 400 series.
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Old August 10th, 2004, 02:57 AM   #19
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Thank you for this information Barbara!
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Old August 11th, 2004, 03:25 PM   #20
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Given that native 16:9 in the XL2 will provide a slightly wider angle of view, will that effect the XL2's ability to work harmoniously with the mini-35 system? Wouldn't you have to zoom through slightly further? That aside, I too am anxious to see how Canon does 24p and cine-gamma!
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Old August 11th, 2004, 04:34 PM   #21
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Devin, the angle of view will remain almost exactly the same with the XL2 since it still use 1/3 CCDs. Anyway you can't zoom any further since you have to remove the lens to put the mini35 directly in front of the CCDs
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Old August 11th, 2004, 05:30 PM   #22
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Ahso, thanks for the insight Jean-Philippe, just goes to show how much I've been fooling around with my home-made mini-35 on my GL1! Forgot that one needn't use the lens on the XL series with the mini-35. Thanks for the help!
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Old August 12th, 2004, 03:45 AM   #23
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Jean-Philippe is basically correct, but let's clarify this a moment!

The field-of-view on the XL2 in 16:9 mode is basically the same
as 4:3/16:9 mode on the XL1!!! It is *NOT* the same as 4:3
mode on the XL2 which has a narrower FOV!

So this will indeed not be a problem with the mini35 as long as
you shoot 16:9. If you shoot 4:3 it will give you a narrower FOV.

The mini35 has been tested a lot with the XL2 already and works
perfectly with the above note applied.
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Old August 12th, 2004, 07:50 AM   #24
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Thanks for clarifying Rob!
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Old August 13th, 2004, 08:26 AM   #25
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Barbara Lowry, any idea when the optional replacement kit for XL2 will be available along with how much? Or am I better off shimming any difference with some cardboard or old baseball cards? (I was trying to be funny)

Thanks.,

Dennis
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Old August 16th, 2004, 02:23 PM   #26
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Soon. Very soon. That question just came up today at ZGC, in fact. I don't have a fix yet, but it will be counted in days, rather than weeks. I'll announce it here when it's ready.
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Old August 18th, 2004, 04:40 PM   #27
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Duncan,

The 'T' in T Stop is for transmission.

A 'T Stop' TRANSMITS the same QUANTITY of light as an f-stop.

The difference is that the f-stop number is the product of a formula: focal length divided by lens diameter, while the t-stop is represents a measurement of the actual amount of light that makes it through a lens. Most lenses are more complicated than just a focal length and a diameter...they typically have numerous pieces of concave and convex glass glued within the barrel of the lens. All these things subtract light...so the t stop, which is measured by the manufacturer, is a more accurate value. So if you're using a light meter and it tells you to use f/5.6, just dial in t/5.6 instead.

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Old August 24th, 2004, 04:38 PM   #28
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Quote:
A 'T Stop' TRANSMITS the same QUANTITY of light as an f-stop.
Minor clarification: a T-stop transmits the same quantity of light as an f-stop IS SUPPOSED TO. Due to light losses within the lens, the f-stop may not be delivering 100% of its potential, but a T-stop is calibrated to show that it's delivering exactly as much as you'd think it should.
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Old August 25th, 2004, 09:39 AM   #29
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Barry,

Yeah, you're right except for the fact that a very simple lens, like a short focal length prime, might in fact have f5.6 on the barrel and indeed deliver f5.6 because of the very simple design of that lens.

So it is true that sometimes the f-stop on a lens delivers the quantity it says it does.

More complicated lenses have T-stops right on the barrel because the additional elements within the lens subtract some light.

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Old August 25th, 2004, 12:06 PM   #30
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Especially zooms...
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