[aslyfox]

. . . I suspect that the higher priced glass was omitted in the 300/4 although the elements were ground to the same shapes.. . . .

interesting, I think I have a confirming source

I have an old book " Complete User's Guide to Pentax K 1000 and P30N/P3N " (c) 1990 which discusses in the back certain Pentax Lenses:

page 146

300mm f 4 A
Minimum aperture : f 32
Closest focus: 4m
Dimensions: 132 x 84mm
Weight:: 850 g
Filter thread: 77mm

A lightweight 300mm general-purpose telephoto in the Pentax-A series, this lens does not use any special glasses . . .

---

Last edited by aslyfox; 11-16-2020 at 12:38 PM.

[onlineflyer]

It has always been assumed that the 300/4 M* and the 300/4 A* are optically identical, but what if they're not? The lens formulae appear identical, except that some diagrams of the M* indicate ED glass, whereas the ones I've seen for the A* don't show that. If anyone has seen diagrams for the A* that show "ED" material being present in the lens, please correct me. I suspect that the higher priced glass was omitted in the 300/4 although the elements were ground to the same shapes.

In the mid-80's Pentax brought out their wonderful "A" lenses and many of the longer ones in include "ED", not just in the lens diagrams, but also in the name engraved upon the lens. The A* 300/4 seems different. It's more in keeping with the excellent 85/1.4 and the 135/1.8 of the same production era. The 85 and the 135 are certainly not shabby company to be lumped in with, but it seems odd from a marketing point of view that Pentax wouldn't mention the presence of "ED" elements.

This could explain the preference that many owners apparently have for the M*. It would also explain my own experience with the A* 300/4.

In my film-and-darkroom days I found that the A* 300/4 was a handy little lens and a pleasure to use, but my own sample, while it seemed fine for 8x10 enlargements, wasn't providing enough resolution for 16x20's. I decided it wasn't quite what I was looking for and sold it to a PF list member who seemed pleased with it. It has since been replaced by a Tamron 60B, an A* 200/2.8 and an F* 300/4.5, any of which can give more useful results. Note that both of these Pentax's contain "ED", not just in the the diagrams, but also in the engravings on the lens bodies.

I wonder if the presence of special glass was deemed more necessary in the longer focal lengths, but less so in the shorter, with an eminently portable 300/4 being used as the cut-off point.

This is all just a matter that I've idly mused about in the past. Again, if anyone has evidence to the contrary, please chime in. It would be interesting to try out the M*, but the presence that F* 300/4.5 in my lens line kind of precludes that.

I wonder if the presence of special glass was deemed more necessary in the longer focal lengths, but less so in the shorter, with an eminently portable 300/4 being used as the cut-off point. So why would the A* 200mm have ED glass, if your logic is correct?

Furthermore, the M 300mm F4 does not have the engraving stating it's ED glass.

[Derek]

I don't know the list prices for the "A" line at that time. It could be that Pentax wanted to keep the A* 300/4 as a cheaper and lighter alternative to the large and expensive 300/2.8. Perhaps they were hoping to push buyers toward the more expensive lens.

In this case I would have preferred them to sell a smaller but higher quality 300/4, complete with "ED".

---------- Post added 11-16-2020 at 11:59 AM ----------

So why would the A* 200mm have ED glass, if your logic is correct?

Furthermore, the M 300mm F4 does not have the engraving stating it's ED glass.

Oops! I missed your second point.

As far as I know, the M* 300 was the the first lens that Pentax used "ED" glass in. There was no large number of of concurrent lenses that needed to be differentiated according to the materials used, and the price charged.

[onlineflyer]

It appears this discussion has been ongoing for years. A quick search directed me to a dpreview page back in 2012. The following is the link:

LBA post - SMC-A* 300mm f4: Pentax SLR Talk Forum: Digital Photography Review

In the thread, an individual posted the following:

"I found this out (about the ED glass in the A* 300/4 and M* 300/4) because a fellow Dutch Pentaxian has scanned lots of Pentax dealer information (provided by the Duth Pentax importer to dealers):

http://fockert.xs4all.nl/~pentax/catalog/05_Objectieven_Filters_Adapters.pdf

Now scroll down to the M* and A* 300/4. In the description of both lenses is mentioned that "low dispersion optical glass" is used. In the case of the A* "ED" is even part of the name."

But perhaps this is the best explanation, posted by another individual:

"Although I have never read anywhere of the A*300/4 having low dispersion glass, I just now read in another of my booklets dated 9/83 that the M*300/4 has low dispersion glass. Now, since the dates of production of the M*300/4 was 1981-1984 and the A*300/4 dates of production was 1984-1989, it is reasonable to assume that the A*300/4 also had low dispersion glass.

Now, that just leaves us with the definition of ED glass which is, in fact, EXTRA low dispersion. So, the M*300/4 and the A*300/4 do not have ED (extra low dispersion) glass, but they do have low dispersion glass."

[Derek]

It appears this discussion has been ongoing for years. A quick search directed me to a dpreview page back in 2012. The following is the link:

LBA post - SMC-A* 300mm f4: Pentax SLR Talk Forum: Digital Photography Review

In the thread, an individual posted the following:

"I found this out (about the ED glass in the A* 300/4 and M* 300/4) because a fellow Dutch Pentaxian has scanned lots of Pentax dealer information (provided by the Duth Pentax importer to dealers):

http://fockert.xs4all.nl/~pentax/catalog/05_Objectieven_Filters_Adapters.pdf

Now scroll down to the M* and A* 300/4. In the description of both lenses is mentioned that "low dispersion optical glass" is used. In the case of the A* "ED" is even part of the name."

But perhaps this is the best explanation, posted by another individual:

"Although I have never read anywhere of the A*300/4 having low dispersion glass, I just now read in another of my booklets dated 9/83 that the M*300/4 has low dispersion glass. Now, since the dates of production of the M*300/4 was 1981-1984 and the A*300/4 dates of production was 1984-1989, it is reasonable to assume that the A*300/4 also had low dispersion glass.

Now, that just leaves us with the definition of ED glass which is, in fact, EXTRA low dispersion. So, the M*300/4 and the A*300/4 do not have ED (extra low dispersion) glass, but they do have low dispersion glass."

Interesting. That would certainly provide some explanation, although this doesn't help with the quote from a book provided by "aslyfox".

Just curious, did that thread that you quoted from say anything about the 85/1.4 and the 135/1.8, a couple of lenses I've sometimes dreamed about? Are they also "low dispersion"? Their diagrams don't hint at anything "ED".

[pentaxus]

Thank you Andrea K! Great info! BTW, Grinding lenses to the same shape with glasses of different refractive indices won't work.

[Derek]

That download of the Dutch catalog just seems to make things murkier. The 300 M* is shown with no special glass mentioned, while the A* is marked as having ED and it's even included in the official name of the lens. However, the only images of an A* 300/4 that I can find do not show this on the barrel. Printing error?

[aslyfox]

my source - " Complete User's Guide to Pentax K 1000 and P30N/P3N " (c) 1990 - discusses the following M, A and F lenses:

[I have omitted all zooms listed there]

under " - M "

18mm f 3.5, 28mm f3.5 shift. 85mm f2.2 soft focus, 100mm f4 smc macro, 135mm f3.5, 135mm f2.5, 500mm f4.5, 1000mm f 8, 1000mm f 11 smc reflex, 2000mm f13.5 smc reflex

Under " - A "

15mm f3,5 smc, 16mm f2.8, 20mm f2.8 smc, 24mm f2.8 smc, 28mm f2 smc, 28mm f2.8 smc, 28mm f2.8 takumar, 35mm f2 smc, 35mm f2.8 smc, 50mm f1.2 smc, 50mm f1.4 smc, 50mm f1.7 smc, 50mm f2 smc, 50 f2.8 macro smc, 85mm f1.4 smc, 100mm f2.8 smc, 100mm f2.8 macro smc, 135mm f2.8 smc, 135mm f1.8 smc, 200mm f4 smc, 200mm f2.8 A ED, 200mm f4 macro ED, 300mm f4, 300mm f2.8 smc ED-IF, 400mm f5.6 smc, 1200mm f8 ED-IF

" - F "

28mm f2.8 50mm f1.7 smc, 50mm f1.4 smc, 50mm f2.8 macro, 100mm f2.8 macro, 135mm f2.8, 300mm f4.5 smc ED-IF, 400mm f2.8 smc, ED-IF, 600mm f4 smc ED-IF

note there is no notation for " star " lenses in any description

[Derek]

my source - " Complete User's Guide to Pentax K 1000 and P30N/P3N " (c) 1990 - discusses the following M, A and F lenses:

[I have omitted all zooms listed there]


note there is no notation for " star " lenses in any description

Thank-you! That's useful.

[kayakfari]

Only in Italian language, sorry:
SMC PENTAX M* 300mm f4

The index has very interesting articles, many about Pentax gears, but you need a translator:
ARTICOLI TECNICI DI ARGOMENTO FOTOGRAFICO by MARCO CAVINA

Google translation:
Google Translate

[Andrea K]

That download of the Dutch catalog just seems to make things murkier. The 300 M* is shown with no special glass mentioned, while the A* is marked as having ED and it's even included in the official name of the lens. However, the only images of an A* 300/4 that I can find do not show this on the barrel. Printing error?

Wrong, in the 300 M* description you can read "low dispersion optical glass". In this catalog they have added informations in the name of some lenses, example "floating" or "ED".

[Derek]

Wrong, in the 300 M* description you can read "low dispersion optical glass". In this catalog they have added informations in the name of some lenses, example "floating" or "ED".

Well, that's all rather ambiguous and I wouldn't put too much reliance in those title descriptions. A moments scrolling took me down the pages to the A 35-105/3.5, which the title describes as having a widest aperture of 4.0, despite the widest aperture of 1:3.5 being plainly visible engraved in the image of the lens a couple of centimeters lower. Another printing error?

Whatever. I still stand by my statement that if the A* 300/4 had some ED glass in it, Pentax would have indicated so on the lens, just as they did with each_and_every_other_"ED"_lens in the "A" series.

[aslyfox]

" . . . Is a puzzlement . . . " for sure

You Tube

You Tube

[ lyrics found here: https://www.metrolyrics.com/a-puzzlement-lyrics-the-king-and-i.html ]

[Derek]

" . . . Is a puzzlement . . . " for sure

Yeah, you can say that again.

[aslyfox]

" I think

I think I am

therefore, I am

I think "

- " the Moody Blues "