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Old Sep 3, 2005, 5:36 AM   #31
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I'm still with peripatetic on this and here some larger MTF's from the same japanese site:

http://cweb.canon.jp/ef/lineup/stand...f18ii/mtf.html
http://cweb.canon.jp/ef/lineup/ef_s/..._56ii/mtf.html
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Old Sep 3, 2005, 10:04 AM   #32
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i honestly don't find the 50 1.8 to be anything special either.. i mean, for 75 bucks it does its job and is a cheap way to add some speed.. but its not an optical masterpiece..
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Old Sep 3, 2005, 10:27 AM   #33
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I don't find the 50 to be particularly special either. In terms of sharpness I can agree that the kit lens and the prime is close. But the thing is (that I know so well after all these months) is that the max aperture you can have at 50mm is 5.6 on the kit lens. That's against 1.8 on the prime. You can stop down twice and it'll still be faster than the kit lens (And if you stop down, there's a possibility that the picture will be sharper than the kit lens wide open).

But I'd rather save up on something else than get this lens, even when it's so cheap :roll:

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Old Sep 3, 2005, 11:30 AM   #34
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peripatetic wrote:
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[ Take it as read that both lenses need to be stopped down, the kit performs not at all at f1.8! And that we are talking about the performance out to 13mm from centre because once again the kit is rather poor 25mm out.]
There was no indications in NHL's post that he was taking these steps, in fact he compared the f/1.8 performance of the prime to the kit's, saying that you need to stop down the prime to get parity with the kit's performance. Comparing the prime's f/1.8 performance to the kit's "wide open" performance is enough to irriate many people, as it did me.

I read this as a different position from yours. You seem to be saying two different things as well -- that technically, the prime is a bit superior, but that in practice, you can't see the difference.

I read NHL's post as implying that technically, the kit is superior, but if you need a low light/bokeh lens, then the prime will fit the bill. Maybe my reading was simply flawed, and that's OK except for others who might have no better reading comprehension than me

Technically, the prime is superior. Let's be clear on that to start. In practice, you may not see a difference, because that depends on a lot of factors, and shooting different subjects with different lighting, etc., which is what one would expect from casual photographic lens comparisons, you do not have strong basis for detailed comparison.

If you have real sharpness tests -- e.g. of buildings at a distance, covering the frame and ideally with some objects at varying distances, taken using a tripod with careful focusing, the prime is visibly superior. Yes, I own these lenses, yes, I've done these tests, and that's why I got upset about the apparent claims that the prime is inferior to the kit. Show me samples that conform these reasonable constraints, and I think I can identify the prime 100% of the time -- it is sharper, and that's what's shown by the data, not the other way around.

The dashed line is the sagittal line, and it's a mistake to ignore this line IMO. If you look at Zeiss or Leica MTF's, they make the sagittal lines solid, and the tangential lines dashed. I might guess that Canon made the tangential lines solid because they often come higher than the sagittal lines, and higher lines look better. Now I doubt that you can make a solid argument one way or another about which lines are more important. I tend to think that sagittal lines more often correspond to practical evaluations, but it's probably more accurate to think that they both matter. So ignoring or minimizing the import of the dashed lines in Canon's chart, is IMO another mistake that tends to be made, together with the other factors identfied and ruled out recently above.

So let's be clear on this: The 50 is technically superior optically, and these can be seen in (my) practical detailed sharpness comparisons. It's not news if some lens comes close to its performance at f/8. It would be news if the 50 prime was inferior to the kit lens.

Some people have reported that they have much more expensive lenses and don't find the 50 1.8 to be remarkable compared to the expensive lenses. I recall the 24-70 f/2.8 L being mentioned in this context, and I see the EF-S 17-85 f/4-5.6 being mentioned in this way above. Fair enough, I say. The domain of recommendation of the prime is not against much more expensive pro/semi-pro lenses, but against consumer lenses.

I often mention that 50 primes can be used as a benchmark for comparison -- that if you don't see an improvement with this lens over another lens, then it's likely you won't see an improvement with an even more expensive lens. Frankly, to me this is a much more interesting statement than anything above, and I'd like to see some detailed comparisons showing some expensive zooms to be much better than the 50 prime. Again, if an expensive zoom matches its performance, it's not news. If it outperforms it, then I'm wrong about this lens being useful as a benchmark.


Edit: Corrected gramatical error that drives me crazy!

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Old Sep 3, 2005, 4:20 PM   #35
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Most telling of course is that I was making a rather strong case for the f8 performance, as you say, big deal, most lenses of any grade can manage decent f8 performance.

Thanks too for the info about how you interpret the MTF sagittal lines, it may well be that Canon de-emphasise this aspect because their lenses are relatively poor in this regard. Certainly the Sigma MTF is generally far better in this respect.

You make good points, and I find myself convinced by your position.

NHL - you're on your own - I've just switched sides. :blah:


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Old Sep 5, 2005, 1:32 AM   #36
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Madwand wrote:
Quote:
The dashed line is the sagittal line, and it's a mistake to ignore this line IMO. If you look at Zeiss or Leica MTF's, they make the sagittal lines solid, and the tangential lines dashed. I might guess that Canon made the tangential lines solid because they often come higher than the sagittal lines, and higher lines look better. Now I doubt that you can make a solid argument one way or another about which lines are more important. I tend to think that sagittal lines more often correspond to practical evaluations, but it's probably more accurate to think that they both matter. So ignoring or minimizing the import of the dashed lines in Canon's chart, is IMO another mistake that tends to be made, together with the other factors identfied and ruled out recently above.
I have realized that some of the above is utterly wrong and indicative of a newbie mistake! That mistake is that reversal of terminology "sagittal" and "meridional"/"tangential" in the interpretation of the Canon charts. Canon does not reverse the convention of representing sagittal lines in solid and tangential lines dashed. This does not invalidate my previous post in any substantial manner, but I would like to offer my humble apology for that error.

The source of my error is apparently this statement:

"The solid lines are meridonial while the dotted lines represent sagittal measurements." from http://luminous-landscape.com/tutori...ding-mtf.shtml

The correct legend is:

"Solid lines on the MTF charts indicate the performance of sagittal lines (parallel to the diagonal of the film), dashed lines are for the perpendicular meridional test target lines."

From http://consumer.usa.canon.com/ir/con...&alpha=MNO

I once again humbly apologize to any who were misled by my statement and brief complaint against Canon.

To be clear, the substance of my argument was not that one line matters more than the other, but that both mattered -- I stand by this, and my opinion on the interpretation of performance of those lenses on the basis of MTF.


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Old Sep 5, 2005, 6:46 AM   #37
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peripatetic wrote:
Quote:
NHL - you're on your own - I've just switched sides. :blah:
Traitor !!! :lol: :-) :G


Madwand

You seem to have taken my post out of context and in isolation - The discussion was about 2 lens (and macro) to encompass a wide range of focal, and what I said was I agree with peripathetic in the overall usefulness of the 50mm f/1.8 against the 17-85mm

The reason that I took the 18-55 as an example is because of it's low price and worse MTF's at the tele as opposed to the 17-85. I agree with everyone as well at f/8 and beyond that the standard lens is sharper, but isn't it correct that this 'limit' the lens potential in the overall discussion (2 lenses and macro)? No one mentioned low-light photography...

I too started out photography with only 1 lens the FD 50 f/1.4 SSC. Zooms were a bugaboo, not the least they were slow too in general - but things has changed: some zooms are now quite good and most are available with f/2.8 and that was the secondary point I tried to get across - If one has a specific need that can be met by 1 focal lenght then by all mean a prime is still perfect.

Again it's just me but I rarely pack my primes anymore when I go on vacation...
(I know they are lighter, but still it's another lens change... and the need to carry many lenses)
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Old Sep 29, 2005, 6:14 PM   #38
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I had the same problem in selecting lenses for my Rebel and I did lots of research on theinternet for almost one year.

Finally I ended up having two lenses beside the one that comes with the camera:

Sigma 15-30mm F3.5-4.5 EX DG ASPHERICAL Price: C$1000

and

Sigma APO 50-500mm F4-6.3 EX DG/HSM Price: C$1500

I still want to buy a macro lens and another camera body before I can tell I am done building the technical lens. (It is frustrating changing lenses while being in a canoe)

The telephoto lens I have is heavy and require monopod in low light condition or after 300mm

but used with my DSLR give me almost 800mm zoom. For wild life photography is great

Though before buyingthe actual telephotoI used for almost one year a

Sigma 70-300mm F4-5.6 APO DG Macrolens.

I think is a goodvalue for the price. It has macro as well.

My website

http://www.hp-zone.com

Cheers


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