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03-15-2007, 11:51 AM   #1
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ID'ing weather-sealed lenses; aperture adjustment question

Hey folks -- two unrelated questions. I'm still waiting to receive my K10D so they're somewhat moot, but here goes:

First, are there any Pentax lenses which aren't weather-sealed? If so, are they in the majority or the minority? What are the limits of the K10D's weather-sealing (the "weather-sealing ceiling", if you will) anyhow?

Second, I know that both tele converters and extensions tubes eat light and require aperture adjustment, but that doesn't affect the lens' focal "sweet spot" aperture, does it? In other words, if a lens has good focus wide open but is best a few stops in, that doesn't change (get worse) if it's on a converter or extension, does it? I can't explain why I think it might, but I just felt the need to ask.

Thanks for indulging the newbie!

03-15-2007, 11:55 AM   #2
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All of the Pentax lenses currently available in stores and fleabay are NOT weather-sealed. Only the new DA* zooms (16-50/2.8 and 50-135/2.8) are weather-sealed. I dunno about extension tubes -- I use a DFA 100 macro lens for close up shots.
03-15-2007, 04:08 PM   #3
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no weather sealed lenses yet, they will be out around may or so (DA*)

and those are the only ones that will have weather sealing for the time being.
as far as the sealing on the k10, you can take it out in the rain and stuff, but still err on the side of caution. the mount is still a big weak spot. one website put it under running water (faucet) and they said it still works. I wouldnt use it on any harder than normal rain.

as far as the extension tubes and TC's cant answer you there, all i know is max aperture gets reduced by 1 to 2 stops (depending if it's a 1.4 or 2x etc, etc.

so if you have an f/2 lens, your widest f/stop would be f/4 (if I calculated correctly)

so if you had a lens w/ a sweet spot @ f/2, then your out of luck
03-16-2007, 03:53 AM   #4
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Thank you both! So, out of curiosity, how much "weather" will an unsealed lens take? Heavy fog? Light rain? I used to shoot with an N2000, so I should know, but that was back in the late 80s. I've been out of the game for a while.

QuoteOriginally posted by -=JoN=- Quote
so if you have an f/2 lens, your widest f/stop would be f/4 (if I calculated correctly)

so if you had a lens w/ a sweet spot @ f/2, then your out of luck
Yep, got it, but not quite the question I meant to ask -- I'll try again. If I'm using an f/2 lens with an extension tube or converter, and my sweet spot was at f/5.6, that doesn't change for some strange reason, does it?

03-16-2007, 04:31 AM   #5
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[QUOTE=amateur6;36999]Thank you both! So, out of curiosity, how much "weather" will an unsealed lens take? [QUOTE]
Lenses are better than cameras, they are cylindrical which sheds water pretty good and they don't have all those indentations that collect water, (not to mention all the buttons etc) I would say that it depends on the lens how weather proof it is. A prime is more weather proof than a zoom. Internal focus more weather proof than external focus etc. I've used my DS and the kit lens in a light rain/mist with no problems, tho I wasn't out for more than 45 minutes to an hour and I wiped the camera down carefully several times.

NaCl(hope that helps)H2O
03-16-2007, 05:27 AM   #6
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QuoteOriginally posted by amateur6:
Yep, got it, but not quite the question I meant to ask -- I'll try again. If I'm using an f/2 lens with an extension tube or converter, and my sweet spot was at f/5.6, that doesn't change for some strange reason, does it?
It shouldn't and I believe it doesn't. However in the case of TC the image quality degrades more or less.
03-16-2007, 06:56 PM   #7
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It does indeed, salty.

QuoteOriginally posted by Matjazz Quote
It shouldn't and I believe it doesn't. However in the case of TC the image quality degrades more or less.
Thank you -- although that does, of course, bring up another question: it seems like extension tubes have the edge over TCs, then -- so why make and/or buy such a thing as a teleconverter?

<--- already bought TC, no tubes.
03-16-2007, 08:28 PM   #8
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QuoteOriginally posted by amateur6 Quote
It does indeed, salty.



Thank you -- although that does, of course, bring up another question: it seems like extension tubes have the edge over TCs, then -- so why make and/or buy such a thing as a teleconverter?

<--- already bought TC, no tubes.
did you see mo's post on his recent acquisition on a 1.4x TC?
he had his sharpest shots yet..

https://www.pentaxforums.com/forums/post-your-photos/4269-my-sharpest-700mm-tele-shots.html


TC's work well with some lenses, and works bad with most.
thing is, it's easier on a wallet to spend around 200 dollars on a TC than buying a 700-1000mm lens.

cheap alternative to super tele shots, and picture quality in some cases does not get degraded

03-17-2007, 08:25 AM   #9
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No, I'd missed those -- fantastic detail on that antenna.

Thanks for the info, as always!
03-17-2007, 09:58 PM   #10
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QuoteOriginally posted by amateur6 Quote
It does indeed, salty.



Thank you -- although that does, of course, bring up another question: it seems like extension tubes have the edge over TCs, then -- so why make and/or buy such a thing as a teleconverter?

<--- already bought TC, no tubes.
They serve completely different purposes, a tele-converter magnifies the central portion of the image, effectively increasing the focal length. They also will magnify the flaws that the lens has at given apertures ie softness and fringing.

While extension tubes are just that, they extend the lens away from the camera, thus allowing the lens to focus closer then it would normally be able to, turning a standard lens into a macro lens (or making a lens "more" macro), mainly used for close-up/MACRO photography.
03-18-2007, 06:46 AM   #11
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QuoteOriginally posted by Cideway Quote
They serve completely different purposes, a tele-converter magnifies the central portion of the image, effectively increasing the focal length. They also will magnify the flaws that the lens has at given apertures ie softness and fringing.

While extension tubes are just that, they extend the lens away from the camera, thus allowing the lens to focus closer then it would normally be able to, turning a standard lens into a macro lens (or making a lens "more" macro), mainly used for close-up/MACRO photography.
Aha! Thanks for that further clarification. Looks like I want to get a good set of tubes, then...
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