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03-09-2009, 07:48 PM   #31
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QuoteOriginally posted by Miserere Quote
I think it would be a very wise move by Pentax to bring out a 600mm f/8 AF MIRROR lens for around $600 street price. Having AF, this lens would not be difficult to shoot with, and given it would be light, a simple monopod would suffice.
Please allow me to be a bit skeptical here.

At f/8 (and, with a central mirror obstruction making the lens effectively even "darker" than f/8 would seem, and with the obstruction lowering the overall contrast to further cripple any chance of AF succeeding), I think that AF would likely be slow and/or erratic even in bright light, and would be very problematic in even just moderate light. I just don't think a 600/8 ~AF~ mirror would work...

[Furthermore, using a monopod with a lens with a razor-thin DOF, with the monopod tilting forward and back, drifting in and out of the plane of decent focus (something that wouldn't happen with a tripod) would also make using a monopod with such a lens a less than ideal solution.]

Don't get me wrong - cat lenses have their place as sometimes necessary compromises (and I enjoy using both a heavy VS1 600/8 and a light Tamron SP 500/8 on occasion). But I don't think that Pentax development should pursue AF mirrors, that's all.

03-09-2009, 07:52 PM   #32
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QuoteOriginally posted by Digitalis Quote
looks at the bokeh of the pic posted above *shudders* it's like they made a telephoto version of the M42 Pentax 55mm f/2 * I think I need to wash my eyes*

What, you mean horrible bokeh and OOF transitions like this?

(Super Takumar 55 f/2)






I love that stuff!

Anyway, This thread at dpreview has a lot of great Africa shots from the Tamron mirror.


.
03-09-2009, 08:52 PM   #33
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QuoteOriginally posted by CFWhitman Quote
As fwcetus pointed out, you should try aperture priority mode.
Already did, works exactly as P mode (doesn't work).
03-09-2009, 08:52 PM   #34
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Now allow me to disagree with you

QuoteOriginally posted by fwcetus Quote
Please allow me to be a bit skeptical here.

At f/8 (and, with a central mirror obstruction making the lens effectively even "darker" than f/8 would seem, and with the obstruction lowering the overall contrast to further cripple any chance of AF succeeding), I think that AF would likely be slow and/or erratic even in bright light, and would be very problematic in even just moderate light. I just don't think a 600/8 ~AF~ mirror would work...
I have a Sigma CAT 400mm f/5.6, which works great on its own. I tested it with a Pentax AF 1.7x TC to produce an equivalent 680mm f/9.4, and it autofocused on a cloudy day. It hunted a little, but not much, and not always. Of course, we've grown up being told that a lens has to be at least f/5.6 to be able to autofocus, but we're also told Christmas presents are from Santa and the Easter Bunny is real. An actual 600mm f/8 would probably have better IQ than my combo too.

QuoteQuote:
Furthermore, using a monopod with a lens with a razor-thin DOF, with the monopod tilting forward and back, drifting in and out of the plane of decent focus (something that wouldn't happen with a tripod) would also make using a monopod with such a lens a less than ideal solution.
If you're using 600mm, I'm going to assume you're shooting something far away, but let's start close at 20m (65.6 ft). At this distance, with an aperture of f/8, the DoF is 0.34m (13.4 inches). I don't know how much you swing your monopod back and forth, but I only move mine at most 1 inch either way, which means that if I focused on an object 20m away it would remain in focus as long as the base of the monopod stayed in the same spot. If you're shooting anything further away than 20m, then your DoF only gets larger, making things even easier for you. DoF increases with the square of the distance, so at 40m your DoF is 1.36m (53.4 inches), or 4 times what it was at 20m (65.6 ft).

Because of all this, I still believe Pentax should release an AF CAT 600mm f/8.

03-09-2009, 09:16 PM   #35
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QuoteOriginally posted by Miserere Quote
Now allow me to disagree with you [...] Because of all this, I still believe Pentax should release an AF CAT 600mm f/8.
Well, Miserere, you do make a good case ("on paper", so to speak). However, I still don't think that an AF 600/8 mirror makes sense as a direction for Pentax to go. (Nonetheless, if Pentax did come out with such a lens, I would be one of those interested in trying it - <g>.)

When you ran your AF test, did you also confirm that the resulting images "nailed" the focus satisfactorily?

Hmmm... I wonder how focus confirmation might work with my mirror lenses... That might be an interesting test...

Now, as for Santa Claus and the Easter Bunny, I do hope you're not gonna disillusion me now... ;-)
03-10-2009, 07:57 AM   #36
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Fred, how about we agree on an AF DA CAT 500mm f/5.6 for $500 street price?
03-10-2009, 08:28 AM   #37
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QuoteOriginally posted by Miserere Quote
Fred, how about we agree on an AF DA CAT 500mm f/5.6 for $500 street price?
That sounds good. It might remind me a bit of the ol' VS1 450/4.5 aspherical cat lens - <g>. Just a bit slower, but with AF - could be interesting... :-)

I might even try it out on the water on whales (something I'd never do with a manual focus 500/8 or 600/8, for example)...
03-10-2009, 08:42 AM   #38
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Ben I don't think any one has pointed out that there is a classic Pentax Reflex 400~600mm f8-f12 lens in the MarketPlace right now. I wish I had the scratch to buy it. Nice and compact for the focal length.

03-10-2009, 10:15 AM   #39
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QuoteOriginally posted by kristoffon Quote
Already did, works exactly as P mode (doesn't work).
It's really odd that it works in manual mode with the green button yet not in Aperture priority mode. If it works with the green button there should be no reason for it not to work just as well with aperture priority. I wonder what's going on there. Again, that's just really strange.

Last edited by CFWhitman; 03-10-2009 at 11:32 AM.
03-10-2009, 12:58 PM   #40
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QuoteOriginally posted by CFWhitman Quote
It's really odd that it works in manual mode with the green button yet not in Aperture priority mode. If it works with the green button there should be no reason for it not to work just as well with aperture priority. I wonder what's going on there. Again, that's just really strange.
Might this be related to same kind of problems with M42 lenses? My 3.5/35mm Auto-Takumar underexposes in Av but works flawlessly with "green button" (AE-L on my K100D). This was discussed here .

Last edited by ovim; 03-10-2009 at 12:59 PM. Reason: typo
03-10-2009, 04:46 PM   #41
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QuoteOriginally posted by jsherman999 Quote
What, you mean horrible bokeh and OOF transitions like this?

(Super Takumar 55 f/2)






I love that stuff!

Anyway, This thread at dpreview has a lot of great Africa shots from the Tamron mirror.


.
Absolutely Gorgeous!!! Bravo...Love these photos. Images often speak louder than words and sometimes to compensate words have to be louder than ones capacity to to be creative. Or should I say over compensate. We have to accept that there are those that judge images purely from a technical stand point. There seem to be laws in creativity, that I personally have never heard of but seem to be in place for those who need to be convinced that for an image to be good, it has to fit some kind of criteria set up by anally retentive under achievers...

None the less, great imagery. ;-)
03-11-2009, 02:11 PM   #42
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QuoteOriginally posted by Rico Quote
Ben I don't think any one has pointed out that there is a classic Pentax Reflex 400~600mm f8-f12 lens in the MarketPlace right now. I wish I had the scratch to buy it. Nice and compact for the focal length.
Thanks. I did have a look at it. I find it to be rather slow at 600mm. If you want a great 600mm f8.0 try to find a Sigma. I had that for a while way back. That and the Tamron are my two favorites.

Ben
03-11-2009, 04:14 PM   #43
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QuoteOriginally posted by benjikan Quote
Absolutely Gorgeous!!! Bravo...Love these photos. Images often speak louder than words and sometimes to compensate words have to be louder than ones capacity to to be creative. Or should I say over compensate. We have to accept that there are those that judge images purely from a technical stand point. There seem to be laws in creativity, that I personally have never heard of but seem to be in place for those who need to be convinced that for an image to be good, it has to fit some kind of criteria set up by anally retentive under achievers...

None the less, great imagery. ;-)
Thank you very much!
03-11-2009, 06:36 PM   #44
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Jsherman999, love those images. Beautiful backgrounds. The images have a great feel to them. Good job.

Like mirror lenses quite a bit. Always wondered how history decided that mirror doughnuts were so bad, while putting up with hexagons from refracting lenses. Hexagons seem as unnatural to me as doughnuts.

Exploring bokeh to the max, I often put odd shaped apertures in my Lens Baby Composer. Some amazing back grounds can be achieved. Benjikan would love it! Try it. Making your own custom apertures - priceless.
thanks
barondla

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03-13-2009, 06:51 AM   #45
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QuoteOriginally posted by barondla Quote
Jsherman999, love those images. Beautiful backgrounds. The images have a great feel to them. Good job.

Like mirror lenses quite a bit. Always wondered how history decided that mirror doughnuts were so bad, while putting up with hexagons from refracting lenses. Hexagons seem as unnatural to me as doughnuts.

Exploring bokeh to the max, I often put odd shaped apertures in my Lens Baby Composer. Some amazing back grounds can be achieved. Benjikan would love it! Try it. Making your own custom apertures - priceless.
thanks
barondla

Check out POINT & SHOOT CONTEST #16 WINNERS in P&S forum. Enter #17. Any brand camera. Any subject. Enter now!
I have been putting off getting a Len Baby. I think it is now the time to give it a shot.

Thanks for reminding me...

Ben
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