[PenPusher]

Lens reviews are one of the most useful aspects of the forum however it has some faults and I think there might be one or two ways in which it might be improved.

It has to be recognised that each review is an individual's opinion which will naturally reflect that persons ambitions for the lens in question, what might seem excellent to one, good to another and awful to yet another. There could be any number of reasons for this going from the camera used, to its sensor and what the reviewer expects to see on their computer screen and even the quality of the screen used.

Telling the difference between one generation of a lens and another is quite difficult because of the number of unknowns. If you take, for example, the standard 50mm F1.8 lens and compare the diagrams provided by Pentax Forums it becomes clear that there has been no optical change over the years, the number of elements and groups have stayed the same but have they ?

While its possible to hazard a guess that the coatings should or might have improved over time and the clarity of the image with it you have really no idea about the actual glass itself, has every element stayed the same or has some different glass been introduced to a special element without the company saying it for improvement or cost saving reasons ?

Then while the diagrams stay the same the size of the lens has differed becoming smaller, has this resulted in changes in the light path resulting in changes to the elements curvature to correct for these changes.

There is a lens diagram for almost every lens Pentax has made except of course the two, usually zooms, you are trying to compare, it would be nice if the forum could rummage around and find the missing diagrams, I would not know where to start. I have a little book somewhere or other where Meyer Optik published all their lens designs with I think the mounts available, of course they were a lens manufacturer keen to sell their wears, Pentax might have preferred to keep theirs away from the prying eyes of other makers.

Somebody may well have asked this sort of thing before if so my apologies for wasting the forums space.

[steephill]

Pentax K-Mount Lenses and Lens Accessories | The K-Mount Page has lens diagrams for every K mount Pentax lens. They don't generally show any sizes though so may not have the level of detail you think might be important.

[AggieDad]

The lens review pages are, indeed, a wonderful resource.

One part of my photography hobby is using vintage lenses. Somehow it is fun to tell someone that has just admired one of my photographs that the lens used is older than they are.

Our lens reviews are my source for what lenses I should be looking for. I look for lenses that are above a selected rating threshold (varies from lens to lens) and not very costly.

I rely on the reviews so much that I created a spreadsheet (well, I taught mathematics) that helps me determine which lenses are best for me. It takes into account the user ratings, the number of reviews, the going price, and a number of other factors. Then with some obscure, gobbledy-gook formula that I created, I come up with a "value" rating for each lens.

When I'm ready to buy a lens, I first look for it in the marketplace listings. If what I want is not for sale, I put a listing in the Buy section. Just last month, after listing a lens I wanted in the Buy section, I had two offers within a day — that's hard to beat.

[GUB]

Lens reviews are one of the most useful aspects of the forum however it has some faults and I think there might be one or two ways in which it might be improved.

It has to be recognised that each review is an individual's opinion which will naturally reflect that persons ambitions for the lens in question, what might seem excellent to one, good to another and awful to yet another. There could be any number of reasons for this going from the camera used, to its sensor and what the reviewer expects to see on their computer screen and even the quality of the screen used.

Telling the difference between one generation of a lens and another is quite difficult because of the number of unknowns. If you take, for example, the standard 50mm F1.8 lens and compare the diagrams provided by Pentax Forums it becomes clear that there has been no optical change over the years, the number of elements and groups have stayed the same but have they ?

While its possible to hazard a guess that the coatings should or might have improved over time and the clarity of the image with it you have really no idea about the actual glass itself, has every element stayed the same or has some different glass been introduced to a special element without the company saying it for improvement or cost saving reasons ?

Then while the diagrams stay the same the size of the lens has differed becoming smaller, has this resulted in changes in the light path resulting in changes to the elements curvature to correct for these changes.

There is a lens diagram for almost every lens Pentax has made except of course the two, usually zooms, you are trying to compare, it would be nice if the forum could rummage around and find the missing diagrams, I would not know where to start. I have a little book somewhere or other where Meyer Optik published all their lens designs with I think the mounts available, of course they were a lens manufacturer keen to sell their wears, Pentax might have preferred to keep theirs away from the prying eyes of other makers.

Somebody may well have asked this sort of thing before if so my apologies for wasting the forums space.

Your points are valid and well accepted by the community.
But there is really no solution to the problem.
Who knows what actual difference there is between say the Super Tak 7 element 50mm 1.4 and the FA 50mm 1.4 - but there probably is.
Given that there is probably no definitive information on this except deep in perhaps Ricoh Japans archives and so then our personal observations are actually quite valuable.
I do wonder whether Japanese enthusiasts know more than us with communications being a bit of a handbrake.
If you think Pentax design evolution is difficult to understand the spare a thought for those trying to understand the Tomioka / Yashica/ Revuenon / etc etc etc relationships.

[Fogel70]

There have been major changes in the optical glass used in lenses since 1960-1970s. Some changes is due to regulations that prohibit use of some materials, and other changes is due to newer materials used and better manufacturing processes of the optical glass. And improvements in producing lens elements.

Some lenses that have been produced over a long time may have several versions of glass formula used. FI a lens like FA50/1.4.

[angerdan]

1. It has to be recognised that each review is an individual's opinion which will naturally reflect that persons ambitions for the lens in question, what might seem excellent to one, good to another and awful to yet another. There could be any number of reasons for this going from the camera used, to its sensor and what the reviewer expects to see on their computer screen and even the quality of the screen used.
2. Telling the difference between one generation of a lens and another is quite difficult because of the number of unknowns.
   If you take, for example, the standard 50mm F1.8 lens and compare the diagrams provided by Pentax Forums it becomes clear that there has been no optical change over the years, the number of elements and groups have stayed the same but have they ?
3. While its possible to hazard a guess that the coatings should or might have improved over time and the clarity of the image with it you have really no idea about the actual glass itself, has every element stayed the same or has some different glass been introduced to a special element without the company saying it for improvement or cost saving reasons ?
4. Then while the diagrams stay the same the size of the lens has differed becoming smaller, has this resulted in changes in the light path resulting in changes to the elements curvature to correct for these changes.
5. There is a lens diagram for almost every lens Pentax has made except of course the two, usually zooms, you are trying to compare, it would be nice if the forum could rummage around and find the missing diagrams, I would not know where to start. I have a little book somewhere or other where Meyer Optik published all their lens designs with I think the mounts available, of course they were a lens manufacturer keen to sell their wears, Pentax might have preferred to keep theirs away from the prying eyes of other makers.
6. ... my apologies for wasting the forums space.

1. That's why an average rating is calculated of all reviews. And the used camera is stated in each review.
2. Each generation has it's own review, not difficult at all.
   If the number of elements keep the same in the technical data from Pentax, it is so.
3. Not different glass has been introduced, because of the optical formula and the glass is manufactured in a batch. That's why Pentax can't just start producing old designs.
4. The optical path and design has nothing to do with the outer barrel of the lens. So the light paths stays the same and no corrections are needed.
5. If anybody does miss lens diagram, he can search for it. Why put these task to the forum?
   There are plenty of sources to check.

Is this topic more about lens design or Site Suggestions and Help - PentaxForums.com ?

[GUB]

If the number of elements keep the same in the technical data from Pentax, it is so.
Not different glass has been introduced, because of the optical formula and the glass is manufactured in a batch. That's why Pentax can't just start producing old designs.

Not sure what you mean here. Surely the glass was made to a formula - why can't that be replicated? (except for the radioactive ones of course.)
But I agree there is not much point in obsessing over element count and similarity without having any idea of the differing refractive properties of the glass.

[Fogel70]

Not sure what you mean here. Surely the glass was made to a formula - why can't that be replicated? (except for the radioactive ones of course.)
But I agree there is not much point in obsessing over element count and similarity without having any idea of the differing refractive properties of the glass.

There are several other material that has been forbidden by regulations. I believe lead was no longer allowed to be used in glass since 2006 by REACH/RoHS regulations, and the regulations in Japan banned lead a few years earlier if I remember correctly.Which was one of the reasons why production stopped on many FA series lenses around that time (2004).

[bdery]

Your intro concerns user lens reviews, but your discussion concerns the information supplied by Pentax, two different topics

If you take, for example, the standard 50mm F1.8 lens and compare the diagrams provided by Pentax Forums it becomes clear that there has been no optical change over the years

As an optical designer, I will say that looking at those diagrams, the only thing which is clear is that there is not enough information available to draw any conclusion whatsoever, apart from the fact that most 50s use the same double Gauss basic design. It is certainly not possible to conclude on potential changes to the design. That being said, again only considering the example of the 50mm lenses, there have indeed not been many changes over time to the basic design (but it'S not the diagrams which tell you this).

hazard a guess that the coatings should or might have improved over time

That is fact, and documented, not a guess

has every element stayed the same or has some different glass been introduced to a special element without the company saying it for improvement or cost saving reasons ?

The company will not reveal the types of glass used for each element, or any other proprietary design choices.

Your best bet to get an idea of how lenses evolved will be to read an in-depth, detailed review showing the evolution of these lenses. Luckily, there is one

Pentax 50mm F1.4 comparison: M, FA and DFA Review - Introduction | PentaxForums.com Reviews

[lytrytyr]

Pentax K-Mount Lenses and Lens Accessories | The K-Mount Page has lens diagrams for every K mount Pentax lens.

Several important diagrams are missing from there, like the DA Ltd 20-40mm zoom, for example:

DA 20-40/2,8-4,0 ED DC WR Limited | The K-Mount Page

The Japanese Ricoh site does have one, however:

HD PENTAX-DA 20-40mmF2.8-4ED Limited DC WR / Standard-Angle Lenses / K-mount Lenses / Lenses / Products | RICOH IMAGING

[RICHARD L.]

There is not much point in obsessing over element count

This is usually right but exceptions have happened. For example, Minolta produced literally hundreds of thousands of "run-of-the-mill" 6 elements/5 groups MD 135 mm f/2.8 lenses over the years, then offered a 4 elements/4 groups MD version that was "stellar" (I have a copy of that lens). This rare lens had 4 thick glass elements and a totally different optical design, it was not sold for a long time and is much sharper from edge-to-edge than the 6 elements version.


Regards

[pepperberry farm]

I think the reviews - lens, camera, accessories - are an important part of PF, especially if taken with a grain of salt...

what I value more are photos taken with the lens, especially if the reviewer is showing either a flaw or an exceptional part of the lens' performance....

and don't forget - the reviews should also be researched along with the lens archives:

Lens Sample Photo Archive - PentaxForums.com

[Lowell Goudge]

I think the best use of the reviews is not the rankings, as many have already po intend out here, and the multiple threads on lens reviews the scores are much too subjective.

Optically, even the worst of lenses made in the 60’s would still score a 7/10 and to distinguish the fine differences in sharpness etc would require optical tools most photographers don’t have.

Therefore what is more important, at least to me, are things that a user, not a scientist might report.

General handling, this comes In to things like location of controls, balance, location of a tripod foot (or lack of one) location of lens straps (or their lack)

There is also ease of focusing and focus throw, but beware, that short focus throw, may mean inaccurate manual focus, and long focus throw may result in missed shots due to focusing speed. Consider for example the following three lenses all of which I own.

Sigma APO 70-200/2.8 EX, focus throw in MF90 degrees, Vivitar Series 1 70-210/3.5 focus throw 180 degrees, Takumar 200/3.5 focus throw 270 degrees

If you are using these lenses and comparing ease of manual focus, the sigma is the fastest, but least accurate, the Takumar is probably most accurate, but cannot be easily changed from infinity to near focus without multiple turns and releases of the focus collar. The vivitar is likely the most useable, because for most shots achieving focus is done within the range of motion you can comfortably achieve with a simple twist of the collar. Yet with 180 degrees of rotation, is accurate enough most of the time.

So depending on what users bought a lens for, influences their ratings.

Same with a tripod foot, on long lenses lack of one might be seen as a negative, but if you shoot all shots hand held, is it? What about carrying. Poorly placed lens straps , or a tripod foot in the wrong place for balance makes a lens hard to carry, while still keeping it out to use.

So I suggest as opposed to criticizing what is wrong with the reviews, accept that they are not scientific, and embrace what they do give you. Usually a real users opinion, as to how the lens performs in the field.

[GUB]

This is usually right but exceptions have happened. For example, Minolta produced literally hundreds of thousands of "run-of-the-mill" 6 elements/5 groups MD 135 mm f/2.8 lenses over the years, then offered a 4 elements/4 groups MD version that was "stellar" (I have a copy of that lens). This rare lens had 4 thick glass elements and a totally different optical design, it was not sold for a long time and is much sharper from edge-to-edge than the 6 elements version.


Regards

I was not implying more elements are better - but rather you couldn't presume two lenses were identical based on element count and element similarity alone. So for instance the FA50mm almost certainly has to have a different optical formula because it doesn't have the Thorium doped elements of the super tak. And yet they are both 7/6.
In the Tak 135mm 3.5s I tend to reach for the earlier taks with their lower count because of some innate sense of prefering them. I don't know whether it is a preferance for the less surfaces , less coating or just an instinctive preference for "older is better"!

[zapp]

There are things that are difficult to accomplish even in the days of internet and AI.
Collect data, share Information… Leica did well sharing information and Erwin Puts compiled the Leica Compendium which is still a lot of work.