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11-23-2018, 11:53 AM - 1 Like   #1
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Lens Oddity: desert days with a sharp and smudgy Ricoh Rikenon P 28-110 2.8-3.8

Like falling trees in a forest, some lenses are never heard of: no user reviews or even empty specs sheets on the web, no mention even as a bullet point in product listings per manufacturer here in PF or in camera-wiki and other more or less exhaustive archives. So they might just as well not really exist, right? Here's one such that accidentally surfaced from neverland:



Apparently Ricoh made a 28-110mm zoom at one point, presumably a few years after and ?modified from the designs of? their 2-touch 28-100 f4 and especially the 1-touch 28-105 f3.5-4.5 ... but with a half to full stop wider aperture at the 28mm end! The wider front end and 2.8-3.8 max aperture are quite reminescent of various manufacturer's 1-touch versions of 28-90 2.8-3.5 or 28-105 2.8-3.8 "stovepipe" zooms sold by Vivitar under its Series 1 designation towards the end of its higher-quality era. Without any information on the production years of this odd Rikenon it's impossible to know, but perhaps both the Rikenon 28-110 and the 28-105 were Ricoh's efforts to take wind out of the sails and sales of the Vivitar stovepipes. They are not reverse engineered reproductions however: the highest magnification of the Vivitars required zooming to 28mm, while the Rikenons do so when zoomed at their longest instead.

They're not particularly likely to be optical gems, but I happen to have a soft spot for lenses with oddly numbered zoom ranges (pun intended). And I happened to be looking for a budget-friendly 24-x or 28-x zoom to take out for field work with my recently acquired K1. So when this mysterious specimen showed up on ebay for $65 it provided a perfect opportunity to satisfy not just my own curiosity, but also let the web discover a lens that until now wasn't even a blip on the radar.

For purposes of soil-related research, I'm currently using the K1's excellent gps capabilities for mapping patches of one of the more iconic desert shrubs of the southwest: Fouquieria splendens aka Ocotillo aka Jacob's staff (aka several other colorful names referring to its stick- and cactus-like appearance). It looks a lot like some of the plants endemic to Madagascar's spiny forest, but belongs to an entirely unrelated group of several species found only in NW Mexico and the southwestern US.

Thanks to their unusual shape they're easy to spot with the naked eye, but mapping them photographically with wide angle lenses tends not to work well with focal lengths under 24mm, because plants that are further away than just a few meters disappear more often than not in the background of more traditionally shaped shrubs such as creosotes, mesquites and jojobas. Also, soil surface details matter for my purposes and it would therefore be great to have a zoom that can capture good detail in the corners at the wide end, but also allow me to zoom in on the surface around my feet without having to get down on my knees every time.

In terms of build, size and weight, the Rikenon 28-110 is very pleasant to work with and it's very similar in dimensions and heft to an SMC DA 16-45, both when zoomed in or at its longest:



Its build is good but not excellent, and the moving parts of its shell all seem to consist of black polycarbonate. The 1-touch zoom is fairly tight, but it nevertheless does slip when pointing down. I'll list the detailed specs below in the following post and show examples of how it performs viz image quality, but for now it's worth pointing out that the "macro" part of its zoom/focus action isn't really macro at all (an underwhelming maximum of 1:6.8x magnification); the green line marking its "macro" range corresponds to a segment of the focus action that is only accessible with the zoom at 110mm, and while you're in this segment it isn't possible to zoom out unless you first turn back the focus into its normal "non-macro" range.


Last edited by pdeley; 11-23-2018 at 04:47 PM.
11-23-2018, 02:41 PM   #2
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As long as the Ricoh pin on the lens does not foul the AF drive pawl one's camera, this might be just the lens for someone needing a good wide-to-short-tele (on FF) fast zoom.

I bring up the pin, mostly because it is always good to do so when considering Rikenon-P lenses and 3rd-party stuff compatible with program exposure Ricoh cameras with the pin on their mount. Many have a fairly benign and generally safe ball-type contact similar to "A" contacts on Pentax lenses. Many others have an actual spring-loaded pin that may drop into the AF drive well, effectively locking the lens to the camera. Sad...very sad...


Steve
11-23-2018, 04:14 PM   #3
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As far as the pin and baffle are concerned, neither interfere with my K1's front bits inside the mount. Being new to Pentax DSLR's though, the only way I could figure out how to make the aperture stop down is to not turn the lens in all the way until the mount lock clicks.

dimensions etc

The lens weighs 460g (16oz and a smidgen), has 8 diaphragm blades, 72mm filter thread and minimum focus distance about 0.75m (just under 30") at 110mm versus 1.5m at other focal lengths. Its maximum length equals 135mm and minimum is 98mm.

performance: the good, the strange and the ugly

Here is an example of several ocotillos in the wild at 28mm and f11:



Clearly there's good news and bad news: the enter is extremely sharp and has no problem resolving all the detail the K1's sensor can handle. On the other hand, things turn soft at the top and bottom edges, and from about the left and right quarters of the image width they go from soft to goddawfully mushy. Here's a crop of the center and some of the softening towards the left quarter. The tip of the second foreground branch is almost exactly at the image's centerpoint:



And here's one of the hot messes in the corners:



The extent of the left and right-side mush varies in complex ways with focal length, aperture and focal distance, in a somewhat strange interaction that I haven't figured out yet. Although the corners never become great, subjects that are about 3-6m away, longer focal lengths and f8 seem to suffer the least. Here's a chain link fence at 5m, f8 and 110mm:



In this case the central circle of sharp and CA-free detail seems to extend just about from top to bottom and the leftmost sixth to the rightmost sixth of the image. The corners are still not great, but they're a lot less mushy than above. Note also that there's a hint of pincushion distortion, this is true across most of the zoom range and gets a little bit more noticeable at its widest end.

Here's the tallest individual ocotillo i've come across in 15+ years, shot at 70mm f8 from about 30m away. Meet Shorty:



Typical ocotillos mostly get to about 4-5m or so, but this handsome fellow (or gal?) towers to 8m. In this shot the top (which was the right side in previous examples) looks pretty much sharp all the way to the tips of the soaring canes, while the bottom 10% of the foreground (left side in previous images) is mushy but probably that's due to being in front of the leading edge of the DOF zone.

---------- Post added 11-23-18 at 05:37 PM ----------

but what about wide open?

As I was mostly hoping for a good landscape lens, I didn't play all that much yet with f2.8 at the widest end of the zoom range. What I've tried so far looked pretty sharp and contrasty in the center circle, but at 28mm you get quite strong vignetting with wide apertures, and at f2.8 the corner pockets become entirely black as if the image circle only covers 95% of full frame. At the long end, things are in many ways different: f3.8 gives the periphery of the image a swirly look while the center turns into a soft focus effect, rather like tamron's 35-105 2.8 adaptall and the early Tokina ATX 28-70 (2.6-)2.8 versions.

Here's an ocotillo flower spike as 2000 pixels wide center crop of a shot taken at 110mm and minimum focus distance in "macro" range, wide open at f3.8:



Compare that with the same subject at 110mm and f8 - with a tiny ant conveniently walking into the picture and showing off the absurdly sharp center:




Conclusions for now:

Overall this odd lens makes more sense on one of the APS-C bodies, since its center sharpness gets kinda insane at apertures greater than f5.6, while the corners and sides can turn out really really bad. Figuring out how to control or use their mushiness isn't going to be straightforward, but I'll definitely keep trying out in different settings. For the ocotillo mapping purpose however, I'm going back to my trusty 16-45 for now ... its corners aren't perfect, but at 28mm it's certainly much better behaved across a much greater part of the image than this Rikenon unicorn.

Last edited by pdeley; 11-23-2018 at 04:41 PM.
11-23-2018, 05:35 PM - 1 Like   #4
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QuoteOriginally posted by pdeley Quote
As far as the pin and baffle are concerned, neither interfere with my K1's front bits inside the mount. Being new to Pentax DSLR's though, the only way I could figure out how to make the aperture stop down is to not turn the lens in all the way until the mount lock clicks.
Enable aperture ring with the custom settings menu...
menu --> C4 --> 24. Using Aperture Ring (set to enabled)
Use M mode to set the shutter speed (lens will not stop down in other than M, X, or B modes).

As for the "pin", it is on the face of the lens' mount flange and has potential to physically interfere with the autofocus drive screw-drive pawl well on the mount flange on the body such that lens cannot be rotated out of the mount. This is a very real hazard dating back to the first Pentax auto-focus film SLRs. For example photos and good discussions:
lens stuck on camera - PentaxForums.com

https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/46816-all-...ens-stuck.html
An early report on this site (over ten years ago) resulted in the lens being removed with the aid of a hacksaw. In other cases a thin "feeler guage" was successfully used to nudge the pin into its recessed position enough to save both lens and camera.

As noted on the above thread, the ball-type are considered safe, even if mount to the camera might feel a little rough. I have a Rikenon-P 50/2.0 with the ball-type pin that I have used on my K-3. I take care to put the body AF/MF switch in the "MF" position to avoid contact with the drive pawl in its extended position, but that is the only precaution I take.

That being said, I had a close call several years ago with the blunt-end pin type where it is an actual spring-loaded straight-cut-end metal pin. I saw the "P" on the aperture ring while rotating the lens on and backed it off before it could drop into the AF drive well. Those and the rounded-end metal pin are considered "deadly".

The important points for risk assessment are:
  • M42 Rikenons never have the pin
  • Rikenon P series are the only K-mount Rikenons that have the "pin" and the hazard is universal for that series
  • 3rd-party lenses with "P" on the aperture ring and lens marked KP or KA/KP or KPA or similar should be carefully examined before mounting to any Pentax AF camera you care about
  • While the ball-type are considered safe, anything other than an almost flush ball should be considered a hazard.
Below is an example of the type with protruding pin with rounded head. This type will very likely jam.


Image from Hin's Photo Corner | Ricoh Pin


Steve


Last edited by stevebrot; 11-24-2018 at 04:48 PM. Reason: Removed extra word
11-24-2018, 03:47 PM   #5
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Is that softness only on one corner? The lens could potentially be decentered.
11-25-2018, 10:08 AM   #6
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Yikes - thanks for the detailed warning and explanation Steve! I was entirely ignorant of the possible problems caused by the Ricoh pin, so I have blithely turned it in all the way multiple times and fortunately taking it off again was no trouble. This particular Rikenon P has a pin with tip shaped like a blunt cone and my K1 was in MF at all times, so maybe that combination explains why it didn't cause any issues:



Zombie at f11 the corners are all as bad as the one shown above unfortunately
11-25-2018, 12:18 PM   #7
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QuoteOriginally posted by pdeley Quote
This particular Rikenon P has a pin with tip shaped like a blunt cone
Wow! That is a new shape to add to the list.

Does it extend further if the aperture ring is set to "P"?


Steve
11-26-2018, 07:24 PM   #8
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No, I don't see any effect of switching to P when the lens is unmounted.

In the case of the various versions of the K-mount, does that mean it definitely won't behave any differently when mounted? Or might there be some form of clever coupling mechanism (kinda like Canon's nFD mount where the aperture only closes if the lens is mounted) that could make the pin move out only when it's turned to P while mounted on a body?

11-26-2018, 08:36 PM   #9
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QuoteOriginally posted by pdeley Quote
No, I don't see any effect of switching to P when the lens is unmounted.

In the case of the various versions of the K-mount, does that mean it definitely won't behave any differently when mounted? Or might there be some form of clever coupling mechanism (kinda like Canon's nFD mount where the aperture only closes if the lens is mounted) that could make the pin move out only when it's turned to P while mounted on a body?
Nope, there is nothing clever. The Rikenon-P mount was designed to be cross-compatible for manual and aperture-priority automatic exposure with competing brands, but that is about it. (I had an Adaptall-2 adapter for Ricoh P at one point and it had nothing special that I remember.)


Steve
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