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Old May 28, 2006, 11:49 PM   #1
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D50 Lenses:

Sigma 18-70mm f/2.8-4.5 at US$360

vs

Nikkor 18-70mm f/3.5-4.5 at US$260


Has anybody used them and made the comparison?

Sigma has larger aperture (but only at the 18mm wide-end), and prices diff is quite small.

I tend to take the Sigma, for its larger aperture than I can shoot my never resting son using higher shutter speed.

But read some opinions that its AF is slow???

Or do you have any other recommendations of other lenses around the similar zoom range w/ large aperture?

Thx!



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Old May 29, 2006, 9:48 AM   #2
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What lenses do you currently have?? If you have the "kit" lens, aside from the extra reach, I don't know that either of these lenses are a significant upgrade. F/2.8 is only an extra 1/2 stop, and that disapears fairly quickly as you zoom in. So for most of the zoom range the aperatures will be the same for both lenses. If you need faster shutter speeds, why not shoot at 400 or even 800 ISO. Noise is hardly visible at 400 and only slightly at 800 (which cleans up nicely). I would definitely try this before spending $260-$360 on a lens that is only marginally better.
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Old May 29, 2006, 12:18 PM   #3
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Thanks for reminder about the overlapping zoom range with the kit 18-55mm lens. And the use of higher ISO !!!

In fact I want a semi-allround lense.

I've had these lenses already, each having their own shortcomings:

1. kit 18-55mm f/3.5-5.6
- too short zoom even for indoor,
- aperture too small.

2. Nikkor 50mm (fixed) f/1.8
- as a DC P&S user migrating to DSLR, not quite used to fixed-length lenses.

3. Tamron 18-200 f/3.5-5.6
- tele-end resolution is quite poor
- aperture too small

I know the extra 70-55=15mm gain in focal length is small, but is quite significant to me for snapshot.

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Old May 29, 2006, 12:43 PM   #4
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Most of the zooms that go to f 2.8, are constant aperature zooms and quite expensive. Otherwise, most primes go to 2.8, but are not as convenient to use. In reality, I rarely need that extra 1/2 stop f2.8 even indoors. I have a SB800 and Sb600 speedlight on almost all the time. Using a diffuser or a pocket bouncer softens the light and provides even lighting that allow me to use low iso's without needing f2.8. I think you're better off getting either flash (if you don't already have one) than spending money on another lens that probably won't give you what you need.
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Old May 30, 2006, 12:35 PM   #5
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Thanks for suggestion of SB800 flash!

I did borrow it for a few weeks and found it quite effective in allowing higher shutter speed.

Sorry, forgot to mention that my BB is only 2.5 yr old (he's my primary target). And I don't want to flash him too often. Even for the built-in flash, I also adjust the flash level to -1.0 most of the time.

Perhaps as when he has grown older (that I feel his eyes won't be harmed by the flash), then I'll use more flash.

That's why I wanted to try larger aperture.

But sometimes when it's a must to flash, I may use the "ceiling-bouncing" method (with external flash only), or cover the flash with some thin white clothes or tissue paper, so not to flash him directly.
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