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05-16-2010, 07:22 PM   #16
ogl
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QuoteOriginally posted by RuiC Quote
Would you be happy with a High-zoom ratio Zoom 30-350mm F5.6 20 elements in 5 groups for APS-C ?

United States Patent Application: 0100033838
I see 30-350/3.6-5.8 for DSLR

05-16-2010, 07:34 PM   #17
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QuoteOriginally posted by ogl Quote
I see 30-350/3.6-5.8 for DSLR
Quote the section it says that in using the quote button. I don't see the focal length of the short end stated clearly. I do see 350 for the long end and an f5.6 which looks like it could be referring to the short end but is unclear. See the quoted sections above. The discussion about aps-c is regarding a previous design and patent number and uses a wide focal length of 35 and AOV of 45 whereas this one states a AOV of 60 at the wide end.

QuoteQuote:
[0009]The zoom lens system disclosed in JUPP No. H04-186212, in which optical performance at the telephoto side is particularly improved, achieves a focal length of 350 mm at the long focal length extremity and an F-number of 5.6; however, the focal length at the short focal length extremity is 35 mm. If such a zoom lens system is used in an APS-C sized digital SLR camera, the angle-of-view at the short focal length extremity is only around 45.degree.

Last edited by Blue; 05-16-2010 at 07:41 PM.
05-16-2010, 10:56 PM   #18
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05-16-2010, 11:06 PM   #19
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QuoteOriginally posted by Blue Quote
Quote the section it says that in using the quote button. I don't see the focal length of the short end stated clearly. I do see 350 for the long end and an f5.6 which looks like it could be referring to the short end but is unclear. See the quoted sections above. The discussion about aps-c is regarding a previous design and patent number and uses a wide focal length of 35 and AOV of 45 whereas this one states a AOV of 60 at the wide end.
yes. 350 mm/f5.6 for long end and 60° at short focal lenght, zoom ratio - 13.2.
30 mm is ~ 70° AOV at 24*36 mm.
35 mm is ~ 63° AOV...
52 mm is ~ 45° AOV...

I didn't catch....


Last edited by ogl; 05-16-2010 at 11:16 PM.
05-16-2010, 11:37 PM   #20
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Can we rule out the possibility of a 20-350 zoom för aps-c? Haven't read all, but if only an AOV is given on the wide side it seems uncertain?
05-16-2010, 11:40 PM   #21
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So is it variable aperture, or fixed? The fixed 5.6 @30mm would be somewhat of a killer, IMO.

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05-17-2010, 02:11 AM   #22
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Pentax DA[*] 26-340mm f/3.6-5.8

QuoteOriginally posted by falconeye Quote
350mm, 13x points to 27mm and 60° points to 30mm image diagonal (APSC).
I just repeat my post.

You all must have missed it. Since I already made clear that the patent describes an APSC lens.

To repeat and make it clear as water:

Pentax DA[*] 26-340mm f/3.6-5.8 for APS-C designed in first half of 2008.

From data provided in Table 5 on p.8 of the patent, one can derive the lens is made for a crop factor of 1.53 (the 100mm figure is the tightest). Moreover, the patent does mention APS-C in saying that a 35mm wide end would not be wide angle for APS-C.

I added a possible *-designation because the patent says it adds a fifth lens group (a second with negative refractive power) to improve optical quality and speed of autofocus. On the other hand, DA*-lenses have been fixed aperture so far. 340mm/5.8 is 59mm so it may be fast enough for a DA* or not.

I thank RuiC for posting the link. However, better read the original document as available here:
HIGH ZOOM-RATIO ZOOM LENS SYSTEM


P.S.
The fact that the lens wasn't released yet may mean that all new DA designs are on hold as far as production releases are concerned. 2008 to March 2009 was the last period where new DA designs were rushed out. The above lens optical design was complete by about that time.

Last edited by falconeye; 05-17-2010 at 02:31 AM.
05-17-2010, 03:19 AM   #23
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More lenses

So, I decided to finetune the search parameters for recent Pentax patents and used the following query string:

Code:
AN/"Hoya" AND AGT/"Greenblum" AND CCL/"359"
on Patent Searching Database
with sort order "Chronological".

Note that categories 354 to 359 all relate to cameras.

Then, a number of known lenses pop up:
- DA 35 Ltd.
- DA* 300

BTW, one is learning that the DA*300 is 290mm f/4.1 and Table1 applies a crop factor of 1.00. It isn't the FA*300/4.5 as the patent describes an 8 element in 6 groups lens. The FA*300 has 9 elements, the A*300 has 8 elements but 7 groups. And the original patent is from April 2007, a year before the DA*300 was released.

So, we now may officially learn from Pentax that the DA*300/4 is a full frame lens.

You may find other interesting patents, like
Camera system and interchangeable lens
which explains how an SDM lens switches between screw drive and ultrasonic. Some may want to check it out because it may answer the question if a lens with broken SDM would still be useable with screw drive.


Others may look at the 61 entries of the list and find more gems ...

P.S.
The "HIGH ZOOM-RATIO ZOOM LENS SYSTEM" is missing from the list although the search parameters fit (bug...).


Last edited by falconeye; 05-17-2010 at 03:30 AM.
05-17-2010, 04:25 AM   #24
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That sounds like an undesireable lens to me. Who'd buy such a lens?
05-17-2010, 06:30 AM   #25
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QuoteOriginally posted by kevinschoenmakers Quote
That sounds like an undesireable lens to me. Who'd buy such a lens?
I might. I like a wide angle but not too wide. I had a lens with a 28mm (42mm on my digital) wide angle for quite a few months and it was fine for me.
05-17-2010, 06:44 AM   #26
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QuoteOriginally posted by jct us101 Quote
I might. I like a wide angle but not too wide. I had a lens with a 28mm (42mm on my digital) wide angle for quite a few months and it was fine for me.
Still though, nearly everyone looking for an APS-C superzoom would get one that goes to 18mm.
05-17-2010, 07:08 AM   #27
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The 250-270mm these lenses now sport is way out there for travel needs and it usually is the weak point. Please give me 17-170mm that performs well at the long end.
05-17-2010, 07:44 AM   #28
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QuoteOriginally posted by kevinschoenmakers Quote
That sounds like an undesireable lens to me. Who'd buy such a lens?
It sounds the same to me, too. I prefer my zooms to be wide rather than long. On APS-C, I'd gladly shorten the long end to 100 or 150 in order to get the wide-end down to 10 or 12.

I don't think that'll ever happen though :-/
05-17-2010, 08:23 AM   #29
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QuoteOriginally posted by falconeye Quote
I just repeat my post.

You all must have missed it. Since I already made clear that the patent describes an APSC lens.

To repeat and make it clear as water:

Pentax DA[*] 26-340mm f/3.6-5.8 for APS-C designed in first half of 2008.

From data provided in Table 5 on p.8 of the patent, one can derive the lens is made for a crop factor of 1.53 (the 100mm figure is the tightest). Moreover, the patent does mention APS-C in saying that a 35mm wide end would not be wide angle for APS-C.

I added a possible *-designation because the patent says it adds a fifth lens group (a second with negative refractive power) to improve optical quality and speed of autofocus. On the other hand, DA*-lenses have been fixed aperture so far. 340mm/5.8 is 59mm so it may be fast enough for a DA* or not.

I thank RuiC for posting the link. However, better read the original document as available here:
HIGH ZOOM-RATIO ZOOM LENS SYSTEM

The didn't say whether it was 60 for a horizontal or diagonal AOV. If it is for horizontal, it would put it in the ball park for a DA* for the 645d system. The time line fits for that also.
05-17-2010, 08:54 AM   #30
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But Auch high ratio doesn't fit usual MF usage though
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