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04-01-2021, 11:46 AM - 14 Likes   #1
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The challenge of the new Pentaprism

One of the Challenger stories, High-grade viewfinder system, reveals a particularly difficult development -- the new pentaprism. From previous product stories, we gained some insight into its motivation. Now we hear from the designers. The pandemic hampered the development for a reason that might not be obvious immediately.


High-grade viewfinder system Designed to achieve high standards | Challengers | PENTAX K-3 Mark III | RICOH IMAGING

"Development of high-refraction glass pentaprism"

"It was only after we began developing this new pentaprism, though, that we realized that we were faced with a formidable task, especially at the processing and assessment stages. High-refraction glass is a highly rigid and fragile material. It was extremely hard work to cut the prism’s edges at specific angles. Initially, we were planning to develop and process this pentaprism at our main pentaprism production factory in Vietnam, and started testing more than 200 production methods. But things didn’t go well.

Of course, when we relocated our pentaprism production facility from Japan to Vietnam, this also involved transferring our expertise and craftsmanship. It’s usually the case in situations such as this that Japanese engineers visit the overseas factory and go through a detailed, repeated verification process with the local staff. Because of the coronavirus pandemic, however, it was impossible for us to make this trip. In the end, we decided to set up a new facility in Japan where our engineering team could develop the technologies necessary to perfect the finishing process, the production step which demanded the largest amount of time. For instance, our engineers experimented with many different production methods and minute testing conditions, finding solutions through a trial-and-error approach in the end."

[my emphasis]


Incidentally, the physical characteristics of the prism suggest a plausible answer for the omission of GPS.

High-refraction glass is rigid and fragile > Need to protect it with a strong metal housing > Replace the conventional plastic prism cover with magnesium alloy > But the RF antennas would be shielded at the prism location > Move the antennas > Only have space for the wireless antennas > Could obtain location info from smartphone > Omit onboard GPS

Of course, there could be other reasons.

- Craig


Last edited by c.a.m; 04-01-2021 at 01:11 PM. Reason: grammar
04-01-2021, 12:03 PM   #2
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I must read that stuff - that's interesting!
04-01-2021, 12:05 PM - 4 Likes   #3
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The prism in the K-3iii is significantly larger than the one in the K-3ii. Not much room for the GPS antenna without making the housing much larger.

K-3ii

k-3iii

Last edited by Not a Number; 04-01-2021 at 12:11 PM.
04-01-2021, 06:27 PM - 2 Likes   #4
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One might think the now characteristics Pentax Pentaprism shape which was originally thought to be homage to heritage Asahi Optical pentaprism styling for the K1 launch could possibly have been implemented to make room for this new pentaprism technology. As others used mirrors or have eliminated the pentaprism altogether Ricoh Pentax forges into a unique specialization/ USP.

Unfortunately the communication of that USP is difficult because the average customer doesn’t care. Especially if it results in higher cost.

04-01-2021, 06:34 PM   #5
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QuoteOriginally posted by Not a Number Quote
The prism in the K-3iii is significantly larger than the one in the K-3ii. Not much room for the GPS antenna without making the housing much larger.
My phone has a GPS, I suspect if I took it apart it is so small I likely would be able to identify it. Maybe your right though, or maybe the just want to sell some of those GPS units.
04-01-2021, 06:51 PM - 2 Likes   #6
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QuoteOriginally posted by Belnan Quote
My phone has a GPS, I suspect if I took it apart it is so small I likely would be able to identify it. Maybe your right though, or maybe the just want to sell some of those GPS units.
The GPS processor chip is quite likely very small. The GPS antenna is dealing with reception of radio frequencies so size-wise it needs to be of certain dimensions to be tunable to GPS radio frequencies and be able to pull in sufficient signal to provide reliable signal input to the GPS processor. This limits how far the antenna can be shrunk. Phones have plenty of room to run antenna around the interior of the case. Given the metal construction of the K3iii, the potential locations of antenna is limited as they need to be outside the metal frame of the camera.
04-01-2021, 07:02 PM   #7
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Don't get me wrong, I think Pentax built a camera that they can be really proud of. It does seem to me that Ricoh is more profit oriented, and it may not be a bad thing if more profit means more development.

04-01-2021, 07:40 PM - 1 Like   #8
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QuoteOriginally posted by Belnan Quote
Don't get me wrong, I think Pentax built a camera that they can be really proud of. It does seem to me that Ricoh is more profit oriented, and it may not be a bad thing if more profit means more development.
What’s to get wrong - your gripe about profit motivation is crystal clear. And IMO off topic from the OPs appreciation of the effort behind the new pentaprism. Surely building a new factory came at cost that will put a dent in the large surplus from selling OGPS1 units to the vast customer base. To be fair, many already have one. (I sold mine).

Love to see a little more love so the glow of this launch lasts a little longer.
04-01-2021, 07:49 PM - 11 Likes   #9
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The very idea of putting the larger, FF-equivalent OVF in an APS-C body was genuinely innovative from the start. Where was the pressure to even think of such a thing? The few optical finders left among other makers mostly had pentamirrors, not pentaprisms, and no one was trying to make those larger or brighter.

There was no competition to drive this costly new development, other than Pentax's own drive to make a better camera.
04-01-2021, 08:59 PM   #10
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QuoteOriginally posted by Marktax Quote
The very idea of putting the larger, FF-equivalent OVF in an APS-C body was genuinely innovative from the start. Where was the pressure to even think of such a thing? The few optical finders left among other makers mostly had pentamirrors, not pentaprisms, and no one was trying to make those larger or brighter.

There was no competition to drive this costly new development, other than Pentax's own drive to make a better camera.
The Nikon D500 (2016) has a pentaprism OVF nearly as large as the K-3 III's.

The pressure comes from EVFs which are growing larger and higher-res.

Over the last 5 years, Nikon has released 9 DSLRs. 3 with pentamirrors, 6 with pentaprisms.
04-01-2021, 09:16 PM   #11
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:"High-refraction glass is rigid and fragile" Does it mean we may expect higher probability of pentaprism destruction. So under the same mechanical impact K3 may survive but K3ii may not?
04-01-2021, 09:27 PM   #12
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QuoteOriginally posted by Belnan Quote
It does seem to me that Ricoh is more profit oriented
Doesn't that apply to ALL businesses?? (excluding non profits of course).
04-01-2021, 11:03 PM   #13
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QuoteOriginally posted by Sqideyes Quote
Doesn't that apply to ALL businesses?? (excluding non profits of course).
Of course, but there a many different strategies. For example you may price something lower to get consumers interested in your products. Or you may overprice all of your products and then gradually lower them as demand diminishes. I'm a scientist, not in marketing so I really dont know the best approach. I'm just suggesting than Pentax is know longer a value oriented brand, at least not the way they used to be.
04-01-2021, 11:29 PM - 2 Likes   #14
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Let's not confuse 'value oriented' with 'cheap'.
A small Toyota is no more value oriented than a Lexus (small same company) just because it is cheaper.
'Value' is more than price. 'Value' is as relevant to quality, features, durability, fit-for-purpose, etc, as it is to price.

Last edited by rod_grant; 04-02-2021 at 04:40 AM.
04-02-2021, 04:22 AM   #15
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Wrong analogy.

Lexus is NOT a small company. Lexus is a HUGE company, or at least a part of one.

From Wikipedia :
"Lexus is the luxury vehicle division of the Japanese automaker Toyota. "
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