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Old Feb 28, 2005, 10:37 AM   #21
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NHL wrote:
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coontie wrote:
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You call this soft ? - http://www.pbase.com/fstopjojo/image/37784093/original
(i.e. not the PBase scaling...)
besides, this one seems to be more sharp:

Sigma 18-125mm F3.5-5.6 DC IF ASP
and more zoom to boot.
... and I agree - f/5.6 is two-stop down from f/2.8!

It's apple vs orange comparison between the two lenses - It's like saying the obvious such as the 70-200 f/4L is sharper than the 70-200 f/2.8L (but what about when the lenses are stopped down to comparable aperture?) :?
Like this: http://www.pbase.com/fstopjojo/image/37805736
Ok, that's what I don't understand. If I take lens A and focus it on a flower at f/2.8. Then I take lens B and focus it at f/22 on a hyperfocal, where half that to infinity is in focus. Now, why shouldn't I be able to compare the sharpness of A vs B within their respective DOF??

What am I missing here? That to me seems apples to apples. Whatever is in focus in whatever lens should be sharp.
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Old Feb 28, 2005, 10:46 AM   #22
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peripatetic wrote:
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You want good Depth-Of-Field even at wide apertures.
when did I say that? I don't want a camera to do what's physically impossible or next to it. Wide apertures have shallow DOF, fine. I know that. But having a sharp picture is not too much to ask. Some lenses take sharp pics some don't. I don't think I should have to pay 1500 for glass to take sharp pics.
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Old Feb 28, 2005, 12:31 PM   #23
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coontie wrote:
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Ok, that's what I don't understand. If I take lens A and focus it on a flower at f/2.8. Then I take lens B and focus it at f/22 on a hyperfocal, where half that to infinity is in focus. Now, why shouldn't I be able to compare the sharpness of A vs B within their respective DOF??

What am I missing here?
What you are missing is 'sharpness' is not a constant - Let take a look at a $1200 lens MTF such as the 24-70 f/2.8L @ 70mm:




The black lines are recorded @ f/2.8 and the blue lines are @ f/8: the same identical lens is clearly sharper when closed down than wide open (regardless of DOF)!
FYI - http://www.canon.com.hk/myContent/Pr...ow_to_read.htm


You are comparing two lenses @ two different apertures - kind of an oxymoron A vs B comparison!
... at f/22 it'll be sharper still - up to a point.
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Old Feb 28, 2005, 2:09 PM   #24
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coontie wrote:
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peripatetic wrote:
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Coontie,

You want good Depth-Of-Field even at wide apertures.
when did I say that? I don't want a camera to do what's physically impossible or next to it. Wide apertures have shallow DOF, fine. I know that. But having a sharp picture is not too much to ask. Some lenses take sharp pics some don't. I don't think I should have to pay 1500 for glass to take sharp pics.
Consider: there is no such thing as DOF really - as you get further away from the focal plane the image progressively loses focus. DOF is a convention whereby it is agreed that the focus is "good enough". This can be (and is) specified in terms of contrast and resolution.

It's not impossible to have large DOP at wide apertures - it all depends on the sensor size. Smaller sensors, like that in the Digilux, will have larger DOP at any given aperture.

( I just had a thought - you weren't using Internet Explorer with automatic resize were you? If so then you should hover the mouse over the bottom-right corner of the image to get the full-size image. IE makes a horrible mess of scaling images. )

Another thing to keep in mind is that Canon DSLRs have an aggressive low-pass (anti-moire) filter in front of the sensor. Images direct from the 20D are quite fuzzy compared to most pro-sumer cameras, and compared to the Digilux they're positively blurry without post-processing.

That's not to say that they don't have the detail required for excellent post-processing however. "Sharpness" of image is a very subjective matter and depends on a whole range of variables.

See this link for some details:

http://www.luminous-landscape.com/tu...harpness.shtml

There is only one objective measure of "sharpness" and that is what is shown on the MTF charts.

One more thing to mention about lenses is that they all have an optimum aperture - usually around f8 or so. If the lens is open wider or narrower things get worse. On an APS-C sensor like the Rebel or 20D for example image quality starts to degrade at around f14 and by f22 can be quite poor. This is due to the circle of confusion being larger than the sites of the photosensors.

I meant no disrespect when I suggested the Leica Digilux 2, it's an excellent camera with an astonishingly good lens. It seemed to me to match your requirements better than a DSLR would. I worry that you might spend $1500 on an XT plus lens and be horribly disappointed in the results.

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Old Feb 28, 2005, 2:57 PM   #25
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hmm.. Ok. I get it. So, then the 18-200mm f3.5 lens is fine for me.

Now, as far as do I really need the dSLR? Good question. I like the freedom to use multiple lenses. I would get 1 lens only because that's all I can afford at this time. That's not to say I will NEVER get another lens, ever.

And that Leica camera. Dude, that's one UGLY apparatus.

Besides, I've a consumer camera now. It takes fine pics, I guess. I'd like to take more action shots during low light and things like that. so I need clean, high ISO capabilities.
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Old Feb 28, 2005, 3:16 PM   #26
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coontie wrote:
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That's not to say I will NEVER get another lens, ever.
Welcome to the slippery slope. :-)
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Old Feb 28, 2005, 3:39 PM   #27
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peripatetic wrote:
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That's not to say I will NEVER get another lens, ever.
Welcome to the slippery slope. :-)
you know what it is, my first camera (that lasted me 7yrs) was a cheap plastic piece of s*** i got at a st. petersburg bazaar because I forgot mine in the states. One button, it kinda took pics most of the time. Not a problem. Take 30 shots, 4 are good, great. Then mrs sees a 10x zoom on a friend's camera -- "we must get that." OK. Got it. Now I tried taking pics of dogs playing -- can't use anything above iso 200. Tried long night shots -- no bulb setting. Tried cropping the trash can -- 3.2mp is not good enough. Kids going down the slope, subject too close, too far, light too dim -- can't focus. Bloody hell!

It's a scam, a SCAM I TELLS YA.
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Old Feb 28, 2005, 3:59 PM   #28
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I hear ya. I actually went back to my film camera (EOS Elan)since I got so tired of digital p&s cameras. Now that it looks like a decent dSLR can be had for a reasonable price, I'm getting back into digital.
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Old Feb 28, 2005, 6:59 PM   #29
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Coontie doesn't want a DSLR, he wants a miracle. The parameters he's seeking don't exist on this planet.

The advantages of a DSLR (no shutter lag, low noise at higher ISO, control over DOF, flexibility in lenses) are offset by cost, complexity and weight. There's no free lunch (or even a cheap one you'd like to eat :-)).


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Old Feb 28, 2005, 8:25 PM   #30
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Wildman wrote:
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Coontie doesn't want a DSLR, he wants a miracle. The parameters he's seeking don't exist on this planet.

The advantages of a DSLR (no shutter lag, low noise at higher ISO, control over DOF, flexibility in lenses) are offset by cost, complexity and weight. There's no free lunch (or even a cheap one you'd like to eat :-)).
alright, alright.. Miracle. Can I get one for less than $600?

at least I'm not one of those suckers that paid $1500 for a 20d 2 weeks ago.
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