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05-25-2012, 01:32 PM   #31
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QuoteOriginally posted by pingflood Quote
Saying that a lens is "slower" or "faster" because of DOF differences is just weird.
Fortunately, nobody said such thing. Unfortunately, this is all you understood from our comments.

05-26-2012, 01:07 AM   #32
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QuoteOriginally posted by Laurentiu Cristofor Quote
Fortunately, nobody said such thing. Unfortunately, this is all you understood from our comments.
Maybe you can explain how the 31/1.8 is "faster" than the 17/0.95 then, using your definition.

Since you fortunately understand (presumably!) that lens speed is directly related to aperture and focal length, this ought to be interesting.

QuoteOriginally posted by Laurentiu Cristofor Quote
twitch just means that the 17/0.95 is the equivalent of a 35/1.9 lens on FF. The FA31 being 1.8 makes it faster (ignoring actual light transmission factors).
So what exactly is "faster" here?
05-26-2012, 09:41 AM   #33
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QuoteOriginally posted by pingflood Quote
Maybe you can explain how the 31/1.8 is "faster" than the 17/0.95 then, using your definition.
I can just explain the difference between what I was saying and what you think I was saying.

The statement that I made (and which was to my knowledge reflecting what twitch meant to say) is the following:

"The FF equivalent lens of the 17.5/0.95 lens is a 35/1.9. A 35/1.9 lens is slower than a 31/1.8 lens (a FF lens). To recapitulate, the 31/1.8 lens is faster than the FF equivalent of the 17.5/0.95 lens"

I'll repeat the last statement:

Statement A: "The 31/1.8 lens is faster than the FF equivalent of the 17.5/0.95 lens"

Note that this statement is not identical to, nor does it mean the same thing as:

Statement B: "The 31/1.8 lens is faster than the 17.5/0.95 lens"

Statement A is what twitch and I are talking about. Statement B is how you read it. You are arguing against something that you made up yourself, so technically you are arguing with yourself, not with us.
05-26-2012, 11:10 AM   #34
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Thanks for clarifying that. I still think you are playing fast and loose with this, but at least I now understand your logic.

05-27-2012, 11:16 PM   #35
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QuoteOriginally posted by pingflood Quote
Thanks for clarifying that. I still think you are playing fast and loose with this, but at least I now understand your logic.
Keep in mind that I was just explaining what twitch meant. As I tried to point out, the FA 31 lacks a corresponding FF body, so there is little point discussing FF equivalents of MFT lenses. Pentax doesn't make FF bodies and MFT systems are not attempting to challenge FF systems - they just attempt to provide the same IQ that APS-C systems provide. By comparison, the APS-C systems never attempted to challenge FF.

What are the fastest zooms for FF? F/2.8 Did APS-C try to best that? Nope. Fastest zooms for APS-C are still F/2.8. But the FT format wanted to challenge APS-C, so what zooms did they provide? F/2. I expect they'll resurface for MFT in a few years. The reason they didn't yet is because MFT went first after P&S upgraders, rather than attempting to compete from start with DSLRs. So what we got so far are entry level offerings, instead of high end ones - but that is changing already with the E-M5.

I don't think FF will ever be mainstream. And I think the APS-C format managed to fell behind in the digital era as well - it may yet be saved by MILCs, but I think the competition of several systems is only going to make the progress harder to achieve. MFT has a great lens lineup and it keeps improving.
05-28-2012, 05:24 AM   #36
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There's some interesting math examples mentioned earlier in the thread.

Now here's me; I rarely use any type of built in automation on a camera - unless the subject has that much action that I somehow can't manually adapt to it as fast as the camera could - which is rare. But then again, I also have several thousands of dollars in meters from various eras; and almost always carry around at least two types of meters.

Minus a flash meter or color meter; when I take a light meter reading using any meter from a five dollar one, to a Minolta 1% Spotmeter, to ones costing onver 1k more than that... It gives me the light meter readings and then three settings to dial in; those three settings are basically - iso, aperature, and shutter, On none of the meters is focal length factored in, nor is the size of the sensor. Darn it would be a Kodak Disc sized sensor or even large format. The math simply soes not change.

So according to a meter; or what hits any image plane; the size of the image doesn't matter; nor does the focal length conversion between full frame and any other size frame; without the use of any type of teleconverter. Case in point; the lower aperature numbers of say f0.9 or even f1.8 will always be better than F4.5 on any format.
05-28-2012, 12:45 PM   #37
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QuoteOriginally posted by Medium FormatPro Quote
So according to a meter; or what hits any image plane; the size of the image doesn't matter;
Of course. The exposure is determined by aperture, ISO setting and shutter speed. But if you want more DOF or less, you will take those exposure parameters and start playing with them - you can lower the ISO and open the aperture or close the aperture and bump the ISO - same exposure, different results in terms of DOF. And of course, if you are playing with the same settings on different formats, they will produce very different results. Do you expect f/5.6 on medium format to produce the same result as f/5.6 on a P&S camera? If yes, then why are you MediumFormatPro and not PointAndShootPro?
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