what are our standards?

[stephen_poe1]

I have decided to post a question -- I am curious of response from the public. Some have agreed and disagreed with me about my ideas expressed in postings in ther past, notably the fact that I am critical of lens testing and the discussion of lens tests as pertinent to photography above all other possible discussions of this art.

 

<p>

 

My major problem is that I believe that these discussions yield little or no useful information, at least to any other than the owner of the lens being tested. If I test my 80 Planar here at home and pronounce it excellent or junk, my neighbor may test his example of the same focal legnth from the same maker and get the opposite result. This is for a variety of reasons:

<p>1) Lens performance varies widely even in lenses made by manufacturers with high QC standards. If I test my lens and tell you its is good or bad how do you know I have tested a good, bad or average specimen of that lens?

<p>2)What tests are we using and how are we grading the results? If I am shooting a high quality printed lens test target and you are shooting a newspaper tacked to the wall isn't it possible that bleed from the printing press in the newspaper shot will skew the result? What if the newspaper curls slightly?

<p>3) Who is grading the results? Some objective scientist/technician or the guy who just spent a hell of a lot more than he should have on a piece of glass and who wants to convince himself that it was money well spent? Or are the tests being graded by someone who writes for a photo magazine that depends upon its advertisers for revenue and this writer also really wants to be invited to the next photo sales conference? (They review the trade shows in these magazines! Does that qualify as journalism then?) Or do you believe that brand x is the best because the salesman just gave you a brochure that said brand x is the best?

<p>4) Are you really testing the lens or your own mechanical aptitude? Unless you hang the target in perfect alignment to the film plane and the camera is correctly focussed, the lens is correctly mounted, free of dust, there are no light sources flaring the lens, etc., you will skew your results.

<p>5)Are you testing the lens or are you testing the lens mount, the camera body, the shutter, the focussing screen, etc? Over or underexposed pictures will skew the result of conventional lens tests. If the film plane is not perfectly aligned you cannot yield a true result. Camera vibration may blur the result. What if one camera has a better lens but the body gives a little mirror slap at a certain shutter speed...it might be beaten in the test by a camera with less vibration but an inferior lens. One of my complaints about one of my famous name 35mm SLRs is that it is possible to improperly insert the lens into the lens mount and it will feel and work as though the lens was inserted properly.

<p>6)I have found that the vast majority of camera problems were opperator errors. Don't you think that this skews the testing process?

<p>7)I avoid the use of filters whenever possible since I think they degrade the image. What if my neighbor tests his lenses against mine while leaving a cheap UV filter in place? Isn't it possible that the filter will skew the test? And if it does, should he leave the filter on if he always uses a UV filter in order to duplicate the way in which he uses his lens out photographing?

<p>8)What will you be using the lens for? Do you photograph test targets for fun or profit? Is every lens suited to be judged by a single, all around test? If I shoot only black and white, for example, is color correction as much of an issue as contrast? And people talk about contrast like more of it is always a good thing...I don't think that is neccessarily true. What if I find that I prefer printing black and white negs with a bit less contrast? Does the "how many stars does this lens have" rating system account for personal preferences in lens performance?

<p>9)What film are you testing on? If you are testing your lens with fresh Tech pan out of thr freezer and I am testing mine with Walgreens 100 speed c-41 that I kept in the glove box of my car for a year do you think our tests will anything when we compare the results?

<p>10)Is it possible that some lenses may be better at rendering a flat target but this will tell us little about how they will function rendering 3 dimensional objects in the real world?

<p>11)Who is developing the film? Over or under developed film will skew the results. Are you judging from negatives, chromes or prints? What kind of film do you shoot and do the tests take this into account? If you are judging from prints, who is making the prints? Don't you think there would be a difference in a 16x20 made in a quiet residential area and a 16x20 made in a darkroom upstairs from a bowling alley? What if I am printing my test print with the finest multicoated enlarging lens while you are printing with an antique fungus spotted lens you clean by polishing with your shirt tail? Do you think the test will show us what our cameras can do? And what if you are a better printer than I am? What if you enlarger is not aligned? What if I aerobicize in my darkroom while printing? Don't you think all of these things could make a good lens look bad or a bad lens look better in comparison?

<p>12)Is it a fair comparison to grade leaf shutter camera lenses against focal plane camera lenses, since, by virtue of their very different construction, they may perform very differently? And how do we compare 6x6 images to 6x7? Do we compare a 6x6 section of the 6x7?

<p>13)Is performance in the lab the best measuring stick for the user who performs the majority of his/her photography OUTSIDE the lab?

<p>Those are my questions; I am throwing them out there to get the discussion going.

[jim_bridges]

I consider lens test other than "in controlled lab conditions" as subjective.

[craig_schroeder]

I have been quietly reading this discussion and thinking about the things that Stefan Poag has stated so well. I too, am lured into these lens test issues, but mainly to confirm a suspicion about one lens in regard to an alternative. A careful user with good technique or a tripod will find their Yashica pix superior to a photographer who primarily hand-holds or has questionable technique. When I have tested, it has confirmed to me that if my sharpness/contrast is off, it is more readily blamed on me or the many steps the film must go through on its way to becoming a picture.

[gordon_vickrey1]

I can't recall agreeing with every single point raised in an argument, but then disagreeing with the conclusion--until now.

 

<p>

 

The issues raised in questions 1-13 strike me as largely valid. Most every point made arises from the context in which it is planted, like some well cultivated tree. But looking at them collectively, they somehow seem to obscure rather than constitute a forest.

 

<p>

 

Stephan repeats his criticism that discussion of lens tests is raised in this forum to higher level of pertinence than other aspects of photography. Certainly, a good case can be made that some folks obsess over the technical aspects of photography to such extent that it detracts from the art of photography. But a hobby is something one dabbles in for satisfaction, and fussing over issues of comparative quality, whether derived from rigorous "objective" tests, or "flakey" subjective impressions, is something that gives satisfaction to more than a few people. This isn't a professional journal. It's an open forum for anyone with any kind of interest in MF. As such, it offers something to just about everyone, equipment oriented obsessives included. That's ok with me. I read what interests me and pass over the rest, and would not care to see the content of this forum narrowed to suit my tastes. Does that mean I have low standards? Yes, with respect to what I think should be imposed on writers to this forum; and no, with respect to my own photography.

 

<p>

 

It is true that there is very little bad MF gear out there. So it follows that many MF photographers would raise the level of technical quality in their photos of if they bestowed more of their attention on their technique and less on their gear. It is also true that some photographers could enhance the artistic elements in their photos by attending more to what they shoot and less to what they shoot with. But with respect to discussing the aesthetic side of photography, remember that this is a text-based forum: we can't see each other's photos here, so it's difficult to discuss artistic elements in any really germane way.

 

<p>

 

I agree with much of what Stefan has written, within a narrow definition of test results. There are exceptions even here, however, because I think there can be some value in a subjective report. For example, I once contributed a report on the performance of a wide angle lens. I wrote of my impressions of its fall-off characteristics and how I reacted to them rather than post numbers derived from a densitometer, specified for a given film, and referenced to optical theory that dictates x amount of fall-off etc., because when it comes to forming a visual understanding, there are times when a description of real-world subjective experiences can actually be more helpful than merely posting a set of numbers.

 

<p>

 

Despite mainly agreeing with Stefan's arguments that comparative subjective tests do little in the way of revealing relevant differences in the performance of individual pieces of equipment, and that we do spend considerable time writing about such things, I don't find any of that to be a cause for complaint. I like the broadness and informality of this forum, and I hope that folks will continue to bring up whatever interests them. Or to complain about the things that does not.

 

<p>

 

--Gordon Vickrey

[scott_eaton]

I guess we have two choices >>

 

<p>

 

(a) Read lengthy post regarding lens testing and lpmm/comparisons

(b) Read lenghty posts criticising those posts

 

<p>

 

I'll take option (a). Even though constant inquiries regarding equipment does get tiring it's getting less annoying than option (b).

 

<p>

 

Stefen, I mean this with respect, but posts do have subject titles, and if you don't like them don't read them.

 

<p>

 

As I've stated previously 1,000 times; "MF equipment varies wildy in quality, more so than any other format".

 

<p>

 

If I drop $1,000 on Nikkor lens I can assume it's "cherry". If I buy a Yashica at a garage sale for $300 I'm going to be leary and test the heck out of it before I crank 10 pro-packs of 120 fujichrome through it for a client that's paying $150 an hour.

 

<p>

 

I've tested lenses a bazillion different ways from optical benches to HeNe lasers to shooting the lowly newspaper against the wall. Even a novice can exceed the capabilities of MF equipment. That's probaly why they're here "bitching" and looking for advice. I also will strongly contend and argue your belief that format considerations exceed equiment considerations.

 

<p>

 

And I'll raise you that roll of Kodak 2415 tech-pan with sheet SO-173 holographic film. 4,000 lp/mm is so much more fun than 400. :^)

 

<p>

 

//scott

[raymond_tai]

stefan,

 

<p>

 

I generally agree with your argument and am trying to read between the lines. Are you trying to say that good photographers yield good results independent of equipment? I would agree with that too. I don't think we can tell which lens Josef Koudelka uses.

 

<p>

 

If I am going to spend money on a lens and I have choices among mediocre to outstanding lenses, of course I would get the "best" possible for the money. However what I consider to be "best" is personal and based on the look I want to achieve on the print. For example I use a 38 year old Canon screw mount lens on my Leica so I have no need to pay attention to standardized lens tests. However I do pay attention to subjective and aesthetic qualities such as lens "bokeh" which to me is most important and would like to read about it in tests. Unfortunately POP Photo, et al., do not test lens "bokeh". Anyway, back to your argument. I think standardized lens tests have their merits and are more important for cheap consumer and third party lenses where any information though incomplete, is beneficial for the purchaser. Whereas for "European flavored" lenses such as Leica, Zeiss or Angenieux, the aesthetic qualities cannot be measured with charts. However this is just my own personal bias so don't send me any nasty e-mail!

 

<p>

 

In short, I think the net provide the means for people from different walks of life to communicate on issues of common interest. Lens tests is just yet another topic.

[tim_brown]

Comments on some of your points:

 

<p>

 

1,12) I tested to see how well my lenses other equipment are. I posted my results here and made no inference about how other peoples lenses might perform.

 

<p>

 

2,9) I described the test conditions in my post.

 

<p>

 

4,5,11) When I underwent testing of my Mamiya TLR lenses I learned far more than the performance of my individual lenses. I learned that visually focusing in the viewfinder is pretty coarse even with the aid of a split prism. From that I learned that using flat USAF targets with focus bracketing doesn't quite cut it. I learned how to modify a Postscript file to make a strip target to go on a stepped wedge to get small, repeatable target distance variations. I learned that focus in the viewfinder does not correspond with focus on the film at the center of the frame and the amount of offset partly compensates for spherical abberation, that tech pan gives significantly better resolution with these lenses than Tmax 100 or Delta 100, that on a 30x30 print (actually printed a small portion of the center) I can't see detail finer than 50lp/mm, even viewed a few inches away. I used strobes to mostly eliminate the effect of vibration.

 

<p>

 

7) I did tests with and without UV filters and saw no resolution difference with a Hoya multicoated filter. This raised my confidence in using these filters.

 

<p>

 

8) A lens that reduces contrast (generally even flare) reduces it more in the shadows than the highlights and does it differently with different subjects and conditions. It's another variable to keep up with. ALso grain is more apparent when printing on a higher contrast paper, all else being equal. Print exposure is more critical too.

[scott_eaton]

I guess I'm not off my soap box yet -

 

<p>

 

As a photographer I've gone from photojournalist, weddings/portrait, commercial, technical / scientific, environmental and did my five years as a custom printer / color analyst. I currently do consulting for closed loop digital systems that require out-put quality not determined by "ink-on-paper" CMS.

 

<p>

 

My own technique over the years has evolved to technical percision and I have a reputation for sharp, vivid images that often challenge the next format size up. When I sell my conventional color prints I have a rule not to allow them to go below 16x20. I push my optics to the limit and expect perfect performance all around. If a subject is closer than 10' and my shutter speed is less than 250 my mirror will be locked up before I'll trip the shutter on my MF gear. When doing long exposures over 1-second I'll lock the shutter open and hold a piece of cardboard in front of the lens and act as a human shutter. The *ONLY* image degredation comes from the lens, or the mass of the photons bouncing off the film.

 

<p>

 

The latter technique has produced one print recently of an illuminated bridge at night shot from a distance of about 150yards. At a print size of 20x24 you can see spider webs in the girders. Consequently, this is one of the sharpest conventional commercial prints I've ever dealt with and have even more pride that it's my own. It's also indistinguishable from 4x5. I sold 5 20x24's of this spectacular image from just showing the contact alone.

 

<p>

 

Yes, a good photographer can produce good images regardless of equipment. But an "exellent" photographer will out-grow his equipment and constantly strive for better results.

 

<p>

 

A couple of other points here. First, commercial photographers submit most of their images to be printed on half-tone presses or other similiar ink-on paper reproduction. This reproduction technique exaggerates image sharpness and contrast. That's why high quality photography books have images that look so good.

 

<p>

 

Also, many if not most of commercial printers accept images from ad agencies and scan them immediatley into digital form to make plates. At this point *BAD* equipment can be made to look like good equipment because of good ol' photoshop and and unsharp mask filter.

 

<p>

 

In short personal experience has taught me that chrome shooters are less concerned about images quality than portrait or color print photographers. They simply don't have to be.

 

<p>

 

//scott

[ryszard_stasinski1]

Really interesting thread.

 

<p>

 

I'd like to add four more warnings concerning lens testing:

 

<p>

 

14) Lenses have different performances for far and near objects,

so does the test results.

 

<p>

 

15) Maximum lp/mm lens resolution is always somewhat subjective.

You are dealing with fuzzy, low-contrast microscopic images, and

your definition of 'maximum resolution' is likely to be somewhat

different from somebody's else.

 

<p>

 

16) Test results are strongly dependent on the target contrast.

 

<p>

 

17) Use of B&W emulsions may lead to overestimation of lens

performance in color photography. Namely, B&W emulsions are

somewhat 'blind' to red light (red is dark in B&W), while because

of physics laws response to the red light is usually the Achilles'

heel of optical systems.

 

<p>

 

Saying all that I must conclude that lens comparisons are both

_interesting_ and _useful_, at least for me. An example - without

reading them I would never know that these oversized

point-and-shot-like cameras holding the name 'Fuji' are so valuable

pieces of equipment.

 

<p>

 

Not everybody can manage to have (and compare) two or more MF

systems, a word from those who can may help a lot.

 

<p>

 

Ryszard Stasinski

[jim_sabo]

I have to agree with most of what Scott said. I'm a stickler for sharpness, and do everything in my power to get it. Therefore, if the lens performance is lacking, I will see it, so lens tests can be important.

 

<p>

 

However, I don't understand Scott's last comment at all. He said "In short personal experience has taught me that chrome shooters are less concerned about images quality than portrait or color print photographers. They simply don't have to be".

 

<p>

 

When I got serious about my images, I moved to slide film. Most of the photographers I know shoot slide film when image quality is critical. I've been exhibiting at some art shows this year, and the most common question is "Why are your colors so much brighter than the others?". Answer: slide film (Velvia/E100) & Ilfochrome prints on the polyester base. Question number 2, "Why are your pictures so sharp?". Answer: technique (tripod, lockup etc), 6x7 format (vs many exhibitor's 35mm), slide film/Ilfochrome.

[eugene_crumpler]

My two cents worth from a hobbist on this subject. Having performed tests on all of the lenses that I use(35 and MF), I have retired some brand name lenses from regular use. The testing results, which are a function of my system, film type, enlarger lens, B&W shooting 95% of the time, etc. are extremenly useful in evaluating the sharpness of my prints. If I get a print that is not up to par, I already know how much of the problem is the lens itself and I can then decide what else was not up to par at the moment the shutter was released.

 

<p>

 

I don't spent a lot of time on lens testing, hopefully only once at the time I aquire the lens. I keep the results of the lens test in my wallet so as to always be availible, as I don't shoot all the time and need to refresh my memory about the 8 lenses that I now use.

 

<p>

 

An example. I was in Paris in January and I wanted to get a night shot of the Effiel Tower. I got all set up, with tech pan in my nikon fm and 55 mm micro-nikkor lens. I realized that I had not packed a cable release and was not able to make an exposure for more than one second. This forced me to use the 55 wide open to have any chance of getting an exposure. I knew when I made the exposures, that a tack sharp 16x20 was not going to be had. I did knew that a 11x14 print would be acceptably sharp. My lack of a cable release kept me from my goal of a really sharp 16x20. My testing and experience let me know that wide open the 55mm tested at 48 l/mm and at F11 I could expect 110 l/mm. 48 l/mm in my experience will not produce a tack sharp 16X blow up no matter how good the rest of my technique. At f11, I would have been assured of that sharp big print, assuming everything else was ok.(I didn't have the MF with me because we were traveling by train, cab and on foot and I was traveling as light as possible) I did make a 16x20 print and it was not real sharp. So a 11x14 is now hanging in my family room.

 

<p>

 

So for me lens testing is useful. My results in l/mm are personal and may not relate to any one elses system.

 

<p>

 

I have only recently gotten on line and I find that this MFD is quite useful and interesting. I read some of the stuff about blad's and other systems, even though I am sold on 6x7 over 6x6, to be knowledgable on other equipment. I read the stuff about Leica's(other forums) even though I am well satisified with my Nikons. I can ocassionally provide some insight about some lesser know item as the result of past use of a lot of different equipment.

 

<p>

 

To wrap up, as stated above, the questions have titles and if you are not interested, don't click!. Ask a question if you don't like the general line of questions and get something going like this

[robert_monaghan]

Hi Y'all ;-)

 

<p>

 

I think you need to perform a static (tripod mounted) lens test when

you first get a lens in order to ensure that it is still in alignment

and working properly. I have found lenses on bad Adaptall-2 mounts that wouldn't close past f/11 to f/16 or f/22 - a quick fix - but probably the reason for the low sale price? ;-) Other lenses appear to have been dropped and mis-aligned, and so should be returned to dealer or seller etc. So you need to perform your own checks on new and esp. used lenses to be able to have confidence in their proper operation. As a side benefit, you should also discover the "sweet spots" or optimal f/stop for best performance for each lens you own. I have a page on some typical camera and (zoom/regular) lens testing tips at http://www.smu.edu/~rmonagha/broncameratest.html plus many links...

 

<p>

 

The real value of MTF lens testing is when it is done by a consistent set of standards, preferably by the same person(s) - such as Chris Perez' et al's work at http://www.hevanet.com/cperez/testing.html In this case, you can identify potential bargains worth looking and testing on an individual basis. Stefan's point against using MTF lpmm figures for lenses is subject to the qualification that many med fmt lenses are 100% tested during assembly (hasselblad/zeiss) so these lenses are presumed to meet these standards - at least when new ;-)

 

<p>

 

I have found that a number of highly regarded and pricey older lenses (e.g., Leica) were great lenses at their introduction, but don't equal performance of later lens designs with better glasses and coatings. On the other hand, I found a late 28mm AIS no-name $15 r.p.m. used lens performs surprisingly well compared to old my 28mm nikkor on the same tripod/film/target setup. My point here is that it is the lens and not the name on it that determines its abilities. A $75 nikkor 75mm lens for Bronica S2A delivers images that I can't split from side by side tests run using my Kowa 6 or Hasselblad 80mm zeiss planar optics (costing ten times as much). Such lens testing may go a long way towards making those of us on a budget a lot happier with our budget choices, after seeing how well most med fmt lenses actually perform.

 

<p>

 

A recent post at (http://www.smu.edu/~rmonagha/mf/kiev88.html) shows that the much maligned Kiev Ukrainian lenses are not the cause of the flare problems often reported or suspected, but rather the flare is due to lack of black flocking in the camera bodies and not the lenses.

In this case, a Mamiya 645 adapter and these inexpensive lenses provide a lot of capability to any photographer who goes beyond what "everybody knows" by actually testing out some lenses and seeing ;-)

 

<p>

 

But Stefan's point about the lens you have in your hand is the only one that counts is a good point, but one that justifies testing your own lens IMHO so all of us should be doing our own testing, right? ;-)

[scott_eaton]

>>However, I don't understand Scott's last comment at all. He said "In short personal experience has taught me that chrome shooters are less concerned about images quality than portrait or color print photographers. They simply don't have to be". <<

 

<p>

 

The vast majority of chrome shooters in the serious amatuer / professional arena submit their images for pre-press work. The mechanical nature of ink-to-paper reproduction "enhances" image sharpness. I simply don't consider this form of reproduction to have anything to do with photography.

 

<p>

 

>>When I got serious about my images, I moved to slide film. Most of the photographers I know shoot slide film when image quality is critical. <<

 

<p>

 

The million dollar question I have is: "what are you going to do with a chrome?." I consider film to be an intermediate step in image reproduction. Yes, projected images from K-25 look marvelous but how practical is it to carry around a slide projector? :^)

 

<p>

 

As another technical matter color negative emulsions hold more information that transparencies.

The grain structure is finer and the tonal scale is far longer. Yes, chromes have more color saturation but how are you going to translate this into a conventionally viewable medium?

 

<p>

 

>>"Why are your colors so much brighter than the others?". Answer: slide film (Velvia/E100) & Ilfochrome prints on the polyester base.<<

 

<p>

 

The number of serious Cibachrome printers over the years I've encountered I could count on my left hand, including myself. The Azo type dyes in Ilford's product are far sharper than those of conventional RA-4 type papers. I used to print with "ciba" and the images the medium produced were nothing less than staggering as far as sharpness and color saturation were concerned.

 

<p>

 

I switched to RA-4 / negative emulsions for 3 reasons:

 

<p>

 

>Fuji has made serious progress in dimensional stability of their papers. (Kodak still lies about it like everything else in that medium)

 

<p>

 

>The chemicals involved with Cibachrome are notoriously worse for disposal than RA-4.

 

<p>

 

>The image dynamics of cibachrome are far more restrictive that color-print papers. You simply can't find enough fire-hydrants, barns, and powder blue 57' Chevys' to keep me printing the stuff. I shoot images with very long tonal scales. Ciba simply can't keep up with me, but that's my personal style.

 

<p>

 

If you are skilled reversal printer then Sir, you have my respect for printing with "the medium of the Gods". It is a small but elite club.

 

<p>

 

A few of my images can be found on my web-site. www.mindspring.com\~wseaton\index.htm

 

<p>

 

//scott

 

<p>

 

 

 

<p>

 

 

When I got serious about my images, I moved to slide film. Most of the photographers I know shoot slide film when image quality is critical. I've been exhibiting at some art shows this year, and the most common question is "Why are your colors so much brighter than the others?". Answer: slide film (Velvia/E100) & Ilfochrome prints on the polyester base. Question number 2, "Why are your pictures so sharp?". Answer: technique (tripod, lockup etc), 6x7 format (vs many exhibitor's 35mm), slide film/Ilfochrome.

[Spearhead]

<i>"Why are your colors so much brighter than the others?". "Why are your pictures so sharp?"</i>

 

<p>

 

When I get asked these types of questions, I know that I must not have done very well at communicating in the image.

[stephen_poe1]

I have gotten a bit of flack from some who wonder why I would post a thread criticizing lens tests.

"If you don't like lens tests don't read them!" seems to be the most popular refrain.

I am not trying to insult people, but I have I think some valid points to make. If using the absolute sharpest lens is a very important thing, by all means use a lens test. BUT PLEASE DO IT YOURSELF! There is a lot of bad science out there masquerading as good science and people are basing these very large and expensive purchases on tests that are absolutely USELESS.

I got stung BAD by bogus test written in a popular photo magazine --- I traded in all my Canon FD stuff at a huge loss for Nikon a number of years ago and no matter how I work it, Nikon has not made my photography any better. I think I would have been better served by keeping the Canon and spending all that money on film...that would have made me feel like I was really doing something to improve my photography. I feel I was very misled by the writers of these magazines and it cost me a lot of money. Part of what misled me were these supposedly scientific tests that I believe to be completely bogus and partisan.

[stephen_poe1]

Oops! Something went wrong and the second paragraph I intended to send got cut off! Here it is:

I think lens tests performed by the individual photographer are fine (in fact I do them myself) providing the means by which the tests are done are known and we all understand that the test indicates the performance of only 1 specimen of that particular lens. I think the ultimate test, however, is usage. If there is a difference in system A lenses and system B lenses will you see that difference in your application? If you won't, will that affect your choice? Camera system A may outperform camera system B in the lab but if Camera system B is easier to use, more reliable and a joy to work with then I will use B and sacrifice a few lpmm that I may not see in the final print anyway.

[ryszard_stasinski1]

Stefan,

 

<p>

 

You are absolutely right about bogus tests in some photo journals.

For example, I can show you that some very popular tests in a German

magazine are sometimes totally misleading, I can provide examples

and a little bit lengthy explanation what probably is the reason.

The one of two only trusty methods of scientific lens testing is

measuring of MTF curves for frequencies not higher than 40 lp/mm,

but after experience with this bogus test I am now collecting

warnings even against the MTF test (they are some!). Note that

e.g. maximum frequency test could be misleading, too - two lens

with frequency limits e.g 90 lp/mm and 120 lp/mm may behave in

exactly the same manner for less than 40 lp/mm, being in this way

undistinguishable in practice.

 

<p>

 

The other scientific method is based on statistics - you should

find few dozens of cooperative lens users, provide them a

questionnaire in which they evaluate the lens, and conclude with

some statistical processing of the answers. This is very cumbersome,

so hardly anybody do it. The results are more 'fuzzy' than those of

MTF test, but they are some advantages, too, e.g. you can ask for

unmeasurable features like ergonomics, and you avoid problems with

lens variability.

 

<p>

 

Notice that evaluations on this forum are close to the statistic

test - somebody describes a lens, somebody else agrees or disagrees,

and after a while an image builds up.

 

<p>

 

Nice shooting with the (tested or untested) lenses!

 

<p>

 

Ryszard