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Old Jul 26, 2005, 9:56 PM   #1
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My understanding is that the lower F stop lets you have faster shutter speed so is this something that is actually useful, or is it very situational, e.g. low light at long zoom, something like a rock concert?

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Old Jul 26, 2005, 10:09 PM   #2
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It is true that a lower f-stop will let you increase shutter speed or allow for lower light situations. ....BUT... The longer the zoom, the more light that's required. To provide a low f-stop on large zooms, the lenes have to be large.
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Old Jul 26, 2005, 11:43 PM   #3
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F2.8 to f3.5 is a little over a half f-stop. That means the shot you can take at 1/100 sec with 2.8 would probably be about 1/70 sec with f3.5. 1/100 works fine with stabilization at 420 mm eq and you could probably get by with 1/70. I would use a burst to be sure.

I regularly get 1/100 at f2.8 on bright sunny days aiming at something in the shade. And something back in the trees on an overcast day can push the limits of what I can handhold with stabilization at f2.8. The difference isn't just for rock concerts unless you take all of your shots out in the sun.

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Old Jul 27, 2005, 2:27 AM   #4
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So it's not exactly a make or break feature to have F2.8 at the long end vs. F3.5? (e.g. FZ20 vs. S2 IS) Not sure if this should be in the "what camera should i buy"...
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Old Jul 27, 2005, 6:18 AM   #5
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420 mm @ f2.8 with a C of C of .025mm at a distance of 50m will give you a DOF of less than 2m. If thats what you want.
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Old Jul 27, 2005, 9:49 AM   #6
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Quote:
So it's not exactly a make or break feature to have F2.8 at the long end vs. F3.5? (e.g. FZ20 vs. S2 IS) Not sure if this should be in the "what camera should i buy"
I wouldn't think so. There are times with my FZ10 that maintains f2.8 that I am using burst mode trying to hit a null moment in movement because I'm pushing the handheld capability. And it would be that much harder with f3.5.

If it were buying a superzoom today it would be a S2. The FZ20 has a better lens for both aperture and CA, but the S2 has better controls and movies that approach camcorder quality.

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420 mm @ f2.8 with a C of C of .025mm at a distance of 50m will give you a DOF of less than 2m. If thats what you want.
Unfortunately none of the non-DSLR digitals can give anywhere near that small a DOF. The 420mm focal length is a 35mm equivalent as a reference. The actual focal length of both cameras being discussed is 72mm at 12X, and you have to use that for the DOF calculations.

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Old Jul 28, 2005, 1:31 AM   #7
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I currently own both a Panasonic DMC-FZ20 and a Canon S2 IS. They're both excellent cameras, but I bought the Canon last month to replace the Panasonic, fully aware of the aperture limitation at full zoom on the Canon. The Panasonic has the better lens, although the Canon's lens is no slouch, and it's plenty good enough for me. Had the Canon been on the market at the time I bought the Panasonic, I would have gotten it instead of the Panasonic, but I hadn't heard a word of its existence at that time. I knew the Panasonic was larger and heavier than I really wanted (it's not huge, but I was used to an Olympus C700), and used proprietary Li-Ion batteries, which I wasn't particularly fond of. I knew I didn't want to go the D-SLR route. Not finding anything else on the market that I liked better, I bought the Panasonic and was quite happy with it. Then I discovered the Canon. Such are the trials and tribulations of buying digital toys.:G I use long zoom a lot and have not (yet) encountered a situation where having the extra half stop would have made a serious difference, and I've taken over a thousand pictures with each in the short time I've had them. I've been in situations where not having access to spare batteries would have been a huge problem. I can carry four sets of NiMh batteries for the Canon for the cost of a single spare for the Panasonic. And if I drain them all in a single day, I can find AAs almost anywhere I might be. Since the Canon is smaller and lighter, I tend to have it with me more often than the Panasonic, so I end up getting photos that I would otherwise have missed. So, for me, lacking half an f-stop at full zoom is not a major concern. Sure, if I could get it without the extra bulk and cost, I'd go for it. Who wouldn't?

You can see some photos I've taken with each at my gallery.
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Old Jul 28, 2005, 1:52 AM   #8
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The original focal length mentioned at the start was 420mm ,that was the correct calculation.
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