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03-29-2009, 09:20 PM   #31
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QuoteOriginally posted by innovation Quote
50-135 on apsc equals to 76.5-206.55. So you needn't worried about missing the 135-200 range, on the contrary, the 50-70 range is need to consider.
while, 70-200 on apsc is 107.1 to 306. Think about it, if using the 50-135 you will miss the range from 200-300. If using the 70-200, you will miss the range from 70-105. Which one you need to buy, depends on which range you truly need.
I hear this sort of comparison regularly, and while I used to have a film SLR, I didn't use it that much or think seriously about it's use at the time, so I never really got used to the field of view represented by say a 70-200 on a 35mm format (and I did have a zoom in that range.) For me, when discussing focal lengths, I'm referring solely to their use on an aps-c camera, and for me, 70-200mm is a much more useful range on aps-c than 50-135mm. In fact when my Tamron 70-200mm comes back from warranty work, I may just sell my 50-135, as even now in the absence of the Tammy, I'm not using the Pentax.

If you have a background in film/full frame 35mm format, then it makes sense to think in those conversion terms, but for many of us, we don't think that way at all, and IMHO, it never makes sense to call a 50-135 a "76.5-206.55mm" when it is after all, just a 50-135mm. Crop factor does not change focal length which is a factor of optics, only apparent magnification and FOV are changed by the sensor size.

03-29-2009, 10:56 PM   #32
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QuoteOriginally posted by heliphoto Quote
<snip> Crop factor does not change focal length which is a factor of optics, only apparent magnification and FOV are changed by the sensor size.
It doesn't change apparent magnification either. That change is solely a result of enlarging the image more for a given print size.

[rant]Crop factor is just that: crop factor! I have prints on my wall that have used a crop factor of as much as 1/3 from Fuji slide film. It was a severe pain to me to have to spend money on a lens that went to 16mm because of that crop factor relative to my FA 24-90.
[/rant]
03-30-2009, 08:28 PM   #33
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I don't think the Pentax can be beat from 50 to 100mm but after that it's not the best.
04-08-2009, 12:59 PM   #34
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here are some first test shots + 100% crops









04-08-2009, 09:34 PM   #35
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QuoteOriginally posted by heliphoto Quote
<snip>

If you have a background in film/full frame 35mm format, then it makes sense to think in those conversion terms, but for many of us, we don't think that way at all, and IMHO, it never makes sense to call a 50-135 a "76.5-206.55mm" when it is after all, just a 50-135mm. Crop factor does not change focal length which is a factor of optics, only apparent magnification and FOV are changed by the sensor size.
True, but sometimes you need the field of view of one or the other. I am lucky enough to have good lenses that cover both. The DA*50-135 is fast, clean, sharp and covers the field of view I was used to with my A 70-210 on film. Comments to the contrary, I find that field of view perfect for soccer.

My 70-210 is now cropped to the fov of a 100-300, and it is an f/4 lens. It is manual focus, but does do all the exposure things possible. It also works quite well with the A 1.4X-S rear converter, which turns it into a 100-300/5.6, retaining all the auto exposure nice things.

I have all the bets covered. I have not yet tried the new-to-me 1.7X AF on the 70-210, but the snow is gradually going away. I just have to rake the gravel off my lawn and see if the grass survived another winter. I will soon be able to shoot robins at the feeders instead of deer.in the planters.
04-09-2009, 07:56 AM   #36
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Just received my DA 50-135 today. The handling is pretty good, AF is very fast. Still need to take some pictures before giving any comments. As heliphoto mentioned, the lens hood is quite annoying. I can't put the cap on when the hood is towards front, and I can't easily change the lens when the hood is reversed.
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