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03-24-2009, 12:51 PM   #16
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QuoteOriginally posted by jensm Quote
All things being equal, it should be easier to do such a design for a cropped sensor than full frame. Perhaps Four Thirds would be the place to look for anybody dreaming of such wide ranges at larger apertures.
True - remember that Panasonic for a while had something like a 28-400 (35mm equivalent FOV) constant f/2.8 on the FZ series cameras.

03-24-2009, 11:38 PM   #17
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QuoteQuote:
Marc Sabatella: True - remember that Panasonic for a while had something like a 28-400 (35mm equivalent FOV) constant f/2.8 on the FZ series cameras.
Marc, can you please tell me which Panasonic model this was? I own an FZ, which covers 27mm to 486mm (35mm equivalent), but in no way at a constant f2.8. The 2.8 is reserved for the shorter focal lengths. At the long end, you are shooting a max aperture of f 4.4, which is wider than the competition, but nowhere near a 2.8.

I do not recall this model you mention, but would like to know which one it is. Thanks.
03-25-2009, 12:21 AM   #18
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To make a 17-70 f2.8, there would be too many compromises in image quality, not to mention the size and cost of such a lens. I would imagine that it would have a huge front element for both the 17mm wide angle, to avoid vignetting, and also for the 70mm end for the large f2.8 aperture requirement. I am not saying that it can't be done, or even that it won't be done, but I think that a 17-70 f2.8 lens would be quite monsterous and monsterously expensive.

Due to the large maximum aperture of f2.8, these lenses need to have very exacting requirements and therefore cost big $, so if you are going to charge big $, you need to make sure that they are optically of the very best quality.

Pentax's best quality lenses have always been limited to 2.5x to 3.5x zoom ratio. Look at the FA*28-70 f2.8, the FA*80-200 f2.8, the DA*50-135 f2.8 which are all 2.5x to 2.7x zoom ratios. The DA*16-50 f2.8 is a 3.125x zoom ratio and even that lens has image quality compromises.

The upcoming DA*60-250 f4 was probably delayed so long due to the fact that they had to get it right with such a large zoom ratio. The other consideration with this lens is that it is a little easier to design long tele zoom lenses with bigger zoom ratios than wide to tele zooms.

The lenses which do have large zoom ratios are usually kept to apertures of f4-5.6 etc as this allows them to be physically smaller and therefore cheaper to manufacture.
03-25-2009, 02:44 PM   #19
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QuoteOriginally posted by Jewelltrail Quote
Marc, can you please tell me which Panasonic model this was?
FZ20 for sure; not sure about the predecessor or successor.

03-25-2009, 09:38 PM   #20
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QuoteQuote:
Marc Sabatela: FZ20 for sure; not sure about the predecessor or successor.
Thank you--just did quick research on it--apparently it was a big hit and took great images. So much to learn, so little time.
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