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Just a few Pentax XW questions

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#1 zakry3323

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Posted 27 July 2021 - 11:28 AM

I'm on a budget and am considering purchasing either the XW30 or XW40 eyepiece as my widefield/finder to replace my Baader Asperhic 31mm, as it's just shy of having enough eye relief for me to be comfortable using it with my dioptrx. I've found a lot of great information about them, but I'd appreciate it if those in the know could confirm a few things for me. 

 

1. Are the 30/40mm SW's the same optical design as the 30/40-R eyepieces? I've read that they have some difference in weight, but I'm unsure if this is due to a change in the housing. 

 

2. If the housing has been changed since they've begun to be produced again, is it still easy to install a dioptrx by removing the eyecup and metal ring, then replacing the eyecup?

 

3. If you've used a dioptrx with either of these yourself, please let me know your experience. Is the field stop visible and sharp with good eye placement, or does one need to look around for it? 

 

Thanks for your time folks smile.gif


Edited by zakry3323, 27 July 2021 - 11:30 AM.

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#2 Starman1

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Posted 27 July 2021 - 02:47 PM

1) Yes, they're the same.

2) The DioptRx fits the same as it does on the shorter focal lengths.

3) That depends.  The DioptRx sacrifices about 8mm of eye relief.  Without glasses, the resultant eye relief

feels comfortable, but don't expect the eye relief to feel long.  Whether you can see the entire field easily depends if you feel comfortable at that distance from the lens.

I can, but I don't know if you can.

 

You could just wear glasses.  If you wear your glasses at the eyepiece, then the APM 30mm Ultra Flat Field becomes another alternative, and it has a slightly longer eye relief than the 30 XW.

It isn't compatible with a DioptRx, however.


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#3 j.gardavsky

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Posted 27 July 2021 - 03:31 PM

I'm on a budget and am considering purchasing either the XW30 or XW40 eyepiece as my widefield/finder to replace my Baader Asperhic 31mm, as it's just shy of having enough eye relief for me to be comfortable using it with my dioptrx. I've found a lot of great information about them, but I'd appreciate it if those in the know could confirm a few things for me. 

 

1. Are the 30/40mm SW's the same optical design as the 30/40-R eyepieces? I've read that they have some difference in weight, but I'm unsure if this is due to a change in the housing. 

 

...

 

Thanks for your time folks smile.gif

The Pentax SMC XW 30 (and  the new R) have the front meniscus for the field correction.

The pentax SMC XW 40 (and the new R) are without the front meniscus.

 

In the new R version, the last four lenses have been regrouped, and possibly redesigned with some new glass materials.

Bonding the lenses might have removed two air-to-glass reflections, and eventually a shorter buildt saving some weight.

 

So, they are not the same.

 

I have still the old Pentax SMC XW 30, to use as a finder EP.

In past, I used to have the Hyperion Aspheric, and sold it after a while.

 

Best,

JG
 


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#4 Greg77

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Posted 27 July 2021 - 03:46 PM

...redesigned 2" XW? There is no official (Pentax- Ricoh) information about that.
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#5 Starman1

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Posted 27 July 2021 - 03:59 PM

Old versions of eyepieces:

30mm--from field lens, 1-2-1-1-1-1 lens arrangement

New version of 30mm eyepiece:

30mm--from field lens, 1-2-1-1-1-1 lens arrangement

This was recently told to me by the sales manager at the Ricoh Sport Optics division.

Only one pair of lenses is cemented.

He did not know if the glass types were changed.

I have no reason to doubt the Pentax person, and I see no conflicting published information.

Older version:

https://www.cloudyni...-buy/?p=9535540

New version:

https://us.ricoh-ima...duct/xw-series/

The configuration image is too small to see well and pixelates if enlarged.

Pentax says: 30 XW-R is 7 elements in 6 groups.  740g.  That's the same weight and lens configuration they quoted a decade ago.

It appears to be neither lighter, nor differently configured.

The -R at the end of the designator, I'm told, refers to "Ricoh", where the others are merely continuations of the eyepieces made when Hoya owned Pentax.

 

Let's not continually beat this dead horse.  The new ones are the same as the old ones.  What kept the prices low was assembly in the Philippines instead of Japan.

That move happened back when Pentax sold to Hoya.


Edited by Starman1, 28 July 2021 - 08:43 AM.

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#6 russell23

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Posted 27 July 2021 - 04:07 PM

Don is right. I've compared old and new XW's. No difference.
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#7 areyoukiddingme

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Posted 27 July 2021 - 04:44 PM

Don is right. I've compared old and new XW's. No difference.

Do you mean the 30 and/or 40?

 

If so, good to know, as I was slightly tempted to try out a 30-R.



#8 Starman1

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Posted 27 July 2021 - 05:18 PM

If you have an older 30mm or 40mm, no reason to buy a 30-R or 40-R.

There might be a reason to try an APM 30 or a Nagler 31 as an alternative, but not a more recent production of the same eyepiece.


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#9 zakry3323

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Posted 27 July 2021 - 06:27 PM

Thank you, this helps a lot!
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#10 SandyHouTex

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Posted 27 July 2021 - 06:28 PM

Here are the new lens configuratins which confirm what JG said above:

 

https://us.ricoh-ima...duct/xw-series/


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#11 Starman1

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Posted 27 July 2021 - 07:00 PM

That's the link I posted above, and the pictures are too small to see and do not blow up well.

Please see my post #5.   I choose to believe what Pentax has directly told me

and what they print in the spec sheets.  There are no new lens configurations.

Ricoh made a mistake adding a -R to the end of the description of the 30mm and 40mm.

Look at the details below the pictures.  Same as they always were.


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#12 j.gardavsky

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Posted 28 July 2021 - 04:02 AM

Back to Pentax XW and XW R in 30mm and 40mm

 

You can see the the difference already on the pictures,

and finally when you ray trace the optics with the green laser pointer beam.

As simple as it is, do it.

 

Regarding the manufacturing,

the Ricoh Imaging plant in the Philippines makes assembly of the digital cameras,

assembly of optics/eyepieces is there not known.

The eyepieces are shipped to the U.S. via the logistic center in the Philippines,

to Europe via the Ricoh Imaging logistic centers in Europe.

 

How many times did we already have this discussion?

 

JG


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#13 Greg77

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Posted 28 July 2021 - 06:05 AM

Green laser points is not the right method to proof redesign of an eyepiece, like XW vs XW-R. Diferent coating and optical material afther a decade or even more?...yes. Redesign...? I don't think so.
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#14 russell23

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Posted 28 July 2021 - 06:58 AM

I doubt there are any changes in the optical design.  In terms of performance the gray box Richoh XW's perform the same as the green box Pentax XW's from what I have seen.  I'm not going to debate it - my eyes are good enough for me on this one.


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#15 j.gardavsky

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Posted 28 July 2021 - 08:28 AM

Don't worry,

 

I have right now contacted the engineers at Teleskop Service in Munich, and we will get the resolve.

 

Otherwise, I am checking all eyepieces I get in my hands with the ray tracing, even those makes which don't disclose the design, like this one,

 

https://www.cloudyni...er-ray-tracing/

 

and not only ray tracing,

but sometimes also on the visibility of the Newton rings in the cemented doublets,

 

https://www.cloudyni...s-newton-rings/

 

and on the thick fluorescent cements,

 

https://www.cloudyni...-the-eyepieces/

 

Best,

JG


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#16 25585

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Posted 28 July 2021 - 08:33 AM

Only real way to find out is to disassemble one of each, and examine them in detail. With XWs, that would nix their waterproofing I expect.


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#17 SandyHouTex

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Posted 28 July 2021 - 08:57 AM

I doubt there are any changes in the optical design.  In terms of performance the gray box Richoh XW's perform the same as the green box Pentax XW's from what I have seen.  I'm not going to debate it - my eyes are good enough for me on this one.

If they changed the glass, which they did in the 30 and 40 XW R, it would have caused a design change.


Edited by SandyHouTex, 28 July 2021 - 08:57 AM.

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#18 j.gardavsky

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Posted 28 July 2021 - 08:58 AM

Only real way to find out is to disassemble one of each, and examine them in detail. With XWs, that would nix their waterproofing I expect.

Not necessary,

as we already have the cut drawings published by the marketing.

And a cemented doublet shows different ray traces, if compared with two air-spaced lenses,

 

Look up the first pic in post #15.

 

Another way is to take an X-Ray pic, to see if 2 lenses are cemented or not.

When X-rayed, you get the lens thickness and radii, which is another helpful info.

 

Best,

JG


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#19 russell23

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Posted 28 July 2021 - 09:22 AM

If they changed the glass, which they did in the 30 and 40 XW R, it would have caused a design change.

I just really don’t see any substantive difference between the new and the old XW’s.   IMO worrying about this is pointless.  

 

But here on CN we sometimes like to over analyze. Based upon my experience with both Pentax and Ricoh XW’s - including the 40mm XW for both, I see no reason to worry about whether or not they made small changes. 

 

The most substantive difference between them is that the Ricoh XW’s have a much weaker rubber smell than the Pentax XW’s.  lol.gif


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#20 Starman1

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Posted 28 July 2021 - 09:23 AM

By definition, if Pentax says "7 elements in 6 groups", only one pair can be cemented.


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#21 M44

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Posted 28 July 2021 - 10:38 AM

I fail to see the difference in both old and newer drawings. May be I need to update my reading glasses.  bugeyes.gif


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#22 csrlice12

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Posted 28 July 2021 - 10:52 AM

By definition, if Pentax says "7 elements in 6 groups", only one pair can be cemented.

This leaves 5 groups of 1....only in astronomy is 1 a group.wink.gif


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#23 M44

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Posted 28 July 2021 - 11:01 AM

This leaves 5 groups of 1....only in astronomy is 1 a group.wink.gif

One element is a group when we consider the air gap. grin.gif


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#24 csrlice12

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Posted 28 July 2021 - 11:05 AM

One element is a group when we consider the air gap. grin.gif

Between the lenses or our ears?lol.gif


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#25 M44

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Posted 28 July 2021 - 11:14 AM

Should be our ears, otherwise we will identify the difference in the views between old and new XWs. :-)


Edited by M44, 28 July 2021 - 11:15 AM.

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