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Asahi Opt. Co., Japan Takumar 1:2.4 f=58mm (M42)
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PostPosted: Sat Mar 07, 2020 10:15 pm    Post subject: Asahi Opt. Co., Japan Takumar 1:2.4 f=58mm (M42) Reply with quote

This thread is to clarify that there is a model of this lens that is not Heliar.

Asahi Opt. Co., Japan Takumar 1:2.4 f=58mm in M42 Mount

M42 Lens 58mm f2.4 Not Heliar


Online Reference

http://www.klassik-cameras.de/Pentax_Takumar_Collection.html

58mm f2.4 Heliar on the left and the 55mm f2.2 Gauss on the right.



This copy in question looks nothing like the 58mm lens shared from the online reference. It actually looks more like the 55mm.

Did Asahi build an intermediate lens from that Gauss design and brand it as 58mm f2.4?


PostPosted: Sat Mar 07, 2020 10:18 pm    Post subject: Reply with quote

This lens has an attitude that I do not yet understand. Under certain situations wide open, the astigmatism can interfere with background if not composed properly. It makes the specular highlights of bokeh look vaguely like the star wars rebel alliance insignia.

May need to compare this with the 55mm f2.2 Preset.






PostPosted: Sat Mar 07, 2020 10:18 pm    Post subject: Reply with quote

This is the bokeh at MFD. M42 Mount.






Sony picture profile is standard.


PostPosted: Sat Mar 07, 2020 10:19 pm    Post subject: Reply with quote

This is stopped down. M42 Mount.

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PostPosted: Sat Mar 07, 2020 10:20 pm    Post subject: Reply with quote

Taken with the M42 version. All photos with a6300 APS-C.

ISO 5000


PostPosted: Sat Mar 07, 2020 10:52 pm    Post subject: Reply with quote

This is the second time I have attempted to open this lens. The first time I was also curious about the optical formula but the threads didn't want to release with ease.

This time, after some heat soak, the threads finally released.

The very rear group would not open, but I was able to inspect the front group. I think this lens has 5 air gapped elements.

















































PostPosted: Sat Mar 07, 2020 11:04 pm    Post subject: Re: Asahi Opt. Co., Japan Takumar 1:2.4 f=58mm (M42) Reply with quote

Quote:


You've got a 55/2.2 with a 58/2.4 name ring. Fabulous eyeballs IMHO! Kudos...


PostPosted: Sun Mar 08, 2020 12:00 am    Post subject: Reply with quote

Unfortunately, I’m rather disappointed since I was seeking the Heliar M42.

It’s more than the name ring. Also, the preset and the set aperture rings both have 2.4 engraved.


PostPosted: Sun Mar 08, 2020 12:44 am    Post subject: Reply with quote

Can name ring be unscrewed from the light baffle?

Looks like some parts might be easy to swap among the three or four lookalikes.


PostPosted: Sun Mar 08, 2020 1:01 am    Post subject: Reply with quote

visualopsins wrote:
Can name ring be unscrewed from the light baffle?

Looks like some parts might be easy to swap among the three or four lookalikes.


It didn't appear to, but I didn't try.

Here is a sample next to the 55mm. Both start with No. 154xxx









PostPosted: Sun Mar 08, 2020 1:17 am    Post subject: Reply with quote

Name ring appears to press fit onto the light baffle or engraved single piece. There are no gaps, pry or glue marks here.












PostPosted: Sun Mar 08, 2020 2:45 am    Post subject: Reply with quote

This may be a transition lens, using up parts from the old series with some new parts, there might be modified parts to fit and work with the other parts, if you get another 58 that is a 58 it would be interesting to see what parts are from which lens and what parts are unique to the hybrid.


PostPosted: Mon Mar 09, 2020 2:43 pm    Post subject: Reply with quote

Lightshow wrote:
This may be a transition lens, using up parts from the old series with some new parts, there might be modified parts to fit and work with the other parts, if you get another 58 that is a 58 it would be interesting to see what parts are from which lens and what parts are unique to the hybrid.


The asahi flex copy of the 58mm 2.4 seems a better bargain though.

My discovery was untimely. Nonetheless, this product was listed with only a single photo. That is now, for me, a buyer's red flag.

This was the photo from the eBay listing. I could have sworn it was the Heliar type.



PostPosted: Mon Mar 09, 2020 4:04 pm    Post subject: Reply with quote

Measure the focal length already! Smile


PostPosted: Tue Mar 10, 2020 3:26 pm    Post subject: Reply with quote

Compare 55 & 58 fov close up using ruler should show difference if lenses have different FL.

However, https://www.google.com/search?q=measure+focal+length

EDIT!!!: Sophie Morel gives 8 methods for measuring FL: https://wp.optics.arizona.edu/optomech/wp-content/uploads/sites/53/2016/10/Tutorial_MorelSophie.pdf


Last edited by visualopsins on Tue Mar 10, 2020 7:01 pm; edited 1 time in total


PostPosted: Tue Mar 10, 2020 5:19 pm    Post subject: Reply with quote

Great job and commitment, Blazer0ne! This is what I understand as a real spirit of research, to unscrew the lens in order to establish the optical formula with certainity!

The difference of the lens' design from the M37 Takumar 2.4/58 explains well the good contrast in your twilight shot.

But is it really a drawback, to have a rare "transitional" version of the lens? I presume it has a collector value that ovecomes the regular M37 version.


PostPosted: Thu Mar 12, 2020 3:27 am    Post subject: Reply with quote

It makes sense to compare this lens to the 55mm f2.2 preset since they appear to have the same optical formula.


PostPosted: Thu Mar 12, 2020 3:30 am    Post subject: Reply with quote

Lightshow wrote:
This may be a transition lens, using up parts from the old series with some new parts, there might be modified parts to fit and work with the other parts, if you get another 58 that is a 58 it would be interesting to see what parts are from which lens and what parts are unique to the hybrid.


Does Asahi Takumar have a history of doing this type of cobbled work on any other lenses?


PostPosted: Sat Dec 12, 2020 6:20 pm    Post subject: Reply with quote

http://forum.mflenses.com/an-evening-walk-with-asahi-takumar-2-4-58-t81340,start,28.html


PostPosted: Sun Dec 13, 2020 1:45 am    Post subject: Reply with quote

HI Blazer,

Your lens definitely seems to be a mystery

As may have been pointed out earlier in this thread, the front lens group is more deep set and the rear lens group of your 58 f/2.4 looks odd - considerably different than my copy.

Take a look at the following images.

The first is a family portrait of the 58mm f/2 Sonnar design in M42, the 55mm f/2.2 Gauss design in M42, the 58mm f/2.4 Helier design in M42 and lastly, the original 58mm f/2.4 in M37. Note that both the M37 and M42 lenses outwardly appear to have the optical construction.

The second photo is a top view of the 55mm f2.2 Gauss and the 58mm f/2.4 Helier. Note here that while the overall dimensions of the lens are nearly identical (48mm in diameter at the top and 34mm in length when focused at infinity), the 55mm f/2.2 is much more deep set than the 58mm f/2.4. There are 8 baffles on the 58mm and about 19 baffles on the 55mm. This would indicate to me that the physical dimensions of the two optical units have to be different in overall length since they both fit in the same outer package, but one has a front element which sits forward of the other.

The third photo is a side view of the 55mm and the 58mm lenses side by side. You can see hear the overall dimensions are nearly identical.

The fourth photo is a bottom view of the 55mm and the 58mm lenses showing the different rear element retaining designs. Your copy of the 58mm lens looks more like the 55mm (shown here on the left side of the image). Also, if Im not mistaken, the front element of your 58mm lens is deeply set like my copy of the 55mm.

I hope this helps.

Paul


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PostPosted: Sun Dec 13, 2020 2:12 am    Post subject: Reply with quote

pdccameras wrote:
HI Blazer,

Your lens definitely seems to be a mystery


It certainly defies perception. Provenance would have been helpful, but it was from eBay.

I agree about counting baffles. The image on the listing was such low rez that it was just not possible to count them.

At the time of purchase, as far as I knew there were no abnormal mashup lenses from AOCo. So, it didn't occur to me that buying the older M37 version and an adapter would have been a safer bet for Heliar.


PostPosted: Sun Dec 13, 2020 2:27 pm    Post subject: Reply with quote

Hi Blazer,

I agree that going with the M37 is probably a safe way to go, however, I don't think this mashup originated from the AOC factory as a common practice. If it came from the factory this way, I would presume it was an assembly error - wrong beauty ring attached to a 55mm f/2.2. To my knowledge, there were never any 58mm f/2.4 lenses made for serial production with the deeper set baffles common on the 55mm lens. I don't think you will see too many of these! I believe the 55mm f/2.2 was seen as an upgrade over the 58mm - a faster, better lens. It would not have behooved AOC to mark an upgraded lens with a lower performing name.

Don't beat yourself up about your purchase. We have all gotten caught in similar traps - honest mistakes or intentional frauds! It's really cool to have the whole set of three early Pentax normals representing Sonnar, Heliar and Gauss designs - a kind of experimentation and search for excellence and manufacturability that would be unheard of today (in my opinion)!

All the best,

Paul


PostPosted: Sun Dec 13, 2020 2:54 pm    Post subject: Reply with quote

pdccameras wrote:
Hi Blazer,

I agree that going with the M37 is probably a safe way to go, however, I don't think this mashup originated from the AOC factory as a common practice. If it came from the factory this way, I would presume it was an assembly error - wrong beauty ring attached to a 55mm f/2.2. To my knowledge, there were never any 58mm f/2.4 lenses made for serial production with the deeper set baffles common on the 55mm lens. I don't think you will see too many of these! I believe the 55mm f/2.2 was seen as an upgrade over the 58mm - a faster, better lens. It would not have behooved AOC to mark an upgraded lens with a lower performing name.

Don't beat yourself up about your purchase. We have all gotten caught in similar traps - honest mistakes or intentional frauds! It's really cool to have the whole set of three early Pentax normals representing Sonnar, Heliar and Gauss designs - a kind of experimentation and search for excellence and manufacturability that would be unheard of today (in my opinion)!

All the best,

Paul


You missed http://forum.mflenses.com/an-evening-walk-with-asahi-takumar-2-4-58-t81340,start,28.html

visualopsins wrote:
Blazer0ne wrote:
Quote:
Co-assembly
When two lens types were in co-production the train of serial numbers moves between alternating batches until the required quantities of each is made, or parts are no longer available. On certain occasions to complete a batch when supplies of parts were exhausted an alternative part has been used deliberately, or in error. Other types of irregularities do occur, some intended and some not.

​A special case of co-production occurs when a model is upgraded. Alternating batches of the old and new models are created until the transition is complete. Some interesting effects were produced under arrangements in play. It is not known if more than one assembly line existed. A single chain serial assembly is assumed.


Interesting! This product method would be very fashionable and green in today's standards. Not a prototype, but a limited run mashup saved from the expense of a recycler or land fill.

This would certainly explain a situation where they took a blank name ring sized for a 55mm f2.2, which has a different cone shape and depth than the heliar version, and engraved upon it 58mm f2.4.

Thanks!


also from https://takumarguide.weebly.com/takumarology.html
Quote:
Takumar 2.4 / 58mm
In 2017 members Pentaxforums found several aberrant lenses (SN 154623, 154662) in the “final” batch of approximately 100 lenses (see lens page) of the Takumar 2.4 / 58mm as it was being discontinued. It is suggested copies were assembled using bodies from the other more popular lens with which it was being co-assembled. (An assembly line cross over?) It seems the correct Heliar bodies were unavailable at the time or in very short supply because their manufacture had ceased. Only 3 single lenses follow this “final” batch (see lens page). The lenses were destined for export, having single distance scales calibrated in Feet, an important goal for the company at the time.


PostPosted: Sun Dec 13, 2020 6:36 pm    Post subject: Reply with quote

Visualopsins,

Thank you for pointing out that link - I did miss those posts!

It fascinating information, but I am confused. Is the conclusion that the final 100 or so 58mm f/2.4's were labelled as such, but were actually 55 f/2.2's because the factory had run out of 58mm f/2.4 bodies? If that's the case, since the 55mm front retainer cone was different, it seems that the only parts that were re-purposed would have been the front trim ring, the focus scale, and the aperture dials. It almost doesn't seem worth it. Or are those final lenses actually 58mm f/2.4 lens units in 55mm f/2.2 bodies? If that's the case would the lens even image properly? It seems the front lens element would be too close to the film plane unless changes were made to the formula.

Best,

Paul


PostPosted: Sun Dec 13, 2020 7:07 pm    Post subject: Reply with quote

pdccameras wrote:
Visualopsins,

Thank you for pointing out that link - I did miss those posts!

It fascinating information, but I am confused. Is the conclusion that the final 100 or so 58mm f/2.4's were labelled as such, but were actually 55 f/2.2's because the factory had run out of 58mm f/2.4 bodies? If that's the case, since the 55mm front retainer cone was different, it seems that the only parts that were re-purposed would have been the front trim ring, the focus scale, and the aperture dials. It almost doesn't seem worth it. Or are those final lenses actually 58mm f/2.4 lens units in 55mm f/2.2 bodies? If that's the case would the lens even image properly? It seems the front lens element would be too close to the film plane unless changes were made to the formula.

Best,

Paul



Based on the text and link provided by Visualopsins:

Maybe the AOCo "Just in Time" production method was reinforced by law of "They Won't Notice." If it was a numbers game back then, well the consumer is not going to complain about a faster better lens. The reseller is not compelled to complain either, because they received the model ordered as labeled.