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11-24-2010, 06:10 AM   #106
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QuoteOriginally posted by patk Quote
they can use whatever methodology they choose. but the object is to demonstrate that existing reviews of one (and preferably several) of the lenses in the database have produced an erroneous conclusion, thus lending substantiation to the claim that the current reviews are borderline worthless.

otherwise i don't see the reason for the fuss. and i certainly don't see any basis for jettisoning the contribution those who have participated in writing reviews have made thus far, which is really where this is leading.
I was having a little fun with the comment. the perception I have is that many people like to complain about the reviews but not as many actually contribute for one reason or another.

It really is a case of put up or shut up.

In going back through the posts, in this thread, there are several underlying issues raised, many valid, many not.

- price changes over time and with many used K mounts is going up, so the average price is a little misleading, but I think price is still relevant to the impression of quality
- rating is highly variable, depending on reviewer and context of the review
- descriptions are not consistent. Many people do not describe the lens in a consistent manner
- sample/test shots some people want sample shots, but others insist they must be either of subjects they (the reader) like, or museum/art gallery quality to make the review worthwhile and credible
- everything is rated 8 or higher. True, but if all people want is gallery/museum quality shots this would be the case also.
- reviewers should also be rated
- some people want a professional review database seperate from the existing one.

Also in reading the posts, I almost get the impression that many people here are confusing the forum threads where someone gets his / her new toy and goes out to take shots with it, forum threads are not reviews,

It should also be pointed out that there is a proposal to add a lens photo database, where posters can put photos taken with a specific lens, or put links to existing posts where they have uploaded images for review. The image database would be considerably different than the review database.

The bottom line is that the existing database is worthwhile, providing people understand why and how it was created. In many instances the lenses reviewed are not in production and the last professional review, if any was made, was possible 40-50 years ago and not relevant.

I do not know how others review lenses, but when I review a lens, (I have done about 8 of my 32 lenses) I put the characteristics I can determine, F-Stops, focus rotation overall impression, any flaws mechanically optically, and how it meters and behaves on my camera. Basically the user detectable performance of the lens. I generally do not post photos taken, that is for the forum not the database. I will describe issues such as vignetting, CA (Lateral or longitudinal) and recommend whether it should be bought or not, or cautions when purchasing.

11-24-2010, 07:20 AM   #107
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QuoteOriginally posted by Lowell Goudge Quote
It should also be pointed out that there is a proposal to add a lens photo database, where posters can put photos taken with a specific lens, or put links to existing posts where they have uploaded images for review. The image database would be considerably different than the review database.
There is a Flickr group dedicated to this very task, where you can search for lenses according to their tags.
Flickr: Pentax SMC - Official Tag Required

I also find the Pentax Photo Gallery good for this. For example the photos submitted for the M50 f4:
PENTAX Photo Gallery

Personally, there is so much in a lens which is important other than IQ, that I think its best for one to just buy the lenses they are interested in, and whittle the selection down through a process of survival of the fittest. I know which lenses I don't use, and just sell them on. I look at the results on the photos, if I dont like them, then I sell them. If you dont print photos, why are you even buying lenses!

The trouble with the more lax approach to analysing a lens' potential is that introduces many other factors which determine image quality. If one of these factors overrides the lens performance, then the lens review based on the image is worthless. For example, a severe limitation in analysis the sharpness of a lens is camera shake. This is thanks to mirror slap and shutter vibration. This means that the image starts overlapping on pixels, going soft and losing the "pop". So anyone determining the sharpness of a lens by a handheld photo is misguided and also misleading others by posting a review.

In fact, some of the lenses I have tested have performed significantly better than their price and rating might lead one to believe, such as the M 100, 135 and 200. I can only think people have not acknowledged the need for tripods (and good ones, like a 190 or 055 Manfrotto, with an in-line ball head, not a bouncy pan and tilt. There is a lot of discussion of this on sites like APUG, where good means something like a Sachtler or a Berlebach coupled with a Markins ball head, in fact, if you want lens IQ, get a tripod).

Pseudo-technical boring contribution to be overlooked by people who say art with a capital "A"For a photo to be able to really pop, contrast needs to be high, this is only possible if the camera moves less than the resolution on the sensor. For example, a sensor with pixels 4um (0.004mm) apart needs to have the front element of the lens move that little during capture. Typically, handheld, people shake the front element at about 10Hz with an amplitude of about 0.1mm. So say a photo taken in 1/50 for a 50mm might appear to be OK at a casual glance, but in fact the resolution is limited to about 25lp/mm. This in turn might seem ok, but in fact it means the contrast at 25lp/mm is zero. That means at 10 lp/mm the contrast is limited to 50% max (consideration of overlap of circles of confusion). 10 lp/mm is where our peak sensitivity is, for normal enlargement (not pixel peeping) and a decent lens offers about 90% contrast or more at this frequency, when tripod mounted.

Last edited by whojammyflip; 11-24-2010 at 07:31 AM.
11-24-2010, 07:22 AM   #108
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QuoteOriginally posted by stevebrot Quote
If a grade of 1 is a Holga and 10 is a Summicron, then a grade of 8 or 9 for most Pentax and Asahi primes is entirely correct and appropriate.

Nuff said...


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11-24-2010, 07:28 AM   #109
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hoojammyflip

your post is entirely worthwhile. The only disagreement I have is with respect to the buy and sell process. A lot of people would balk at this and consider it too expensive. Considering most lenses are probably between an 8 and 9 in reality any way, unless there is a severe limitation in the performance of a lens, I think the best approach is to work with the lens to learn how to take advantage of what it does. Most amature photographers will at some point need to realize they will never be "great" if they can't learn to work within the limitations of the equipment.

Perhaps the "database of photos" should just be a search engine on the photo gallery.

11-24-2010, 07:36 AM   #110
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indeed, buying and selling a lot of lenses is not to everyone's liking, particularly my wife!
11-24-2010, 07:42 AM   #111
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QuoteOriginally posted by Lowell Goudge Quote
I generally do not post photos taken, that is for the forum not the database. I will describe issues such as vignetting, CA (Lateral or longitudinal) and recommend whether it should be bought or not, or cautions when purchasing.
This is exactly the sort of thing that a nice shot will show you.

Hey, this lens has vignetting, here's a shot at a parade I took that shows when it can be a problem.

That's a real-world example of a criticism of a lens, which I think would be very helpful. No, this picture does not have to be for a museum, but show me a shot in the real world. Show me some interesting conditions where the lens falls flat, or is an exceptional performer. If you tell me there is CA, don't post an 100% crop of some leaves from the extreme corner of a shot, show me the picture of the full landscape, and allow me to judge whether the CA is acceptable to me.

Some people are much more sensitive to these sorts of things, and will complain about them, while others may not even SEE the problem!
11-24-2010, 07:59 AM   #112
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QuoteOriginally posted by paperbag846 Quote
This is exactly the sort of thing that a nice shot will show you.

Hey, this lens has vignetting, here's a shot at a parade I took that shows when it can be a problem.

That's a real-world example of a criticism of a lens, which I think would be very helpful. No, this picture does not have to be for a museum, but show me a shot in the real world. Show me some interesting conditions where the lens falls flat, or is an exceptional performer. If you tell me there is CA, don't post an 100% crop of some leaves from the extreme corner of a shot, show me the picture of the full landscape, and allow me to judge whether the CA is acceptable to me.

Some people are much more sensitive to these sorts of things, and will complain about them, while others may not even SEE the problem!
OK worthwhile example here, Vignetting.

A while back, someone posted a shot and inquired about exposure on his FA50F1.4. THe shot included a living room rug, table and some toys. in looking at the shot, (and uploading into my photo editor) I could see that wide open he had vignetting in the corners to about 3/4 of a stop.

Out of curiosity, I tested my K50F1.4 and Supertak 50F1.4 (version 1) on all my bodies, and found that all combinations vignette wide open to about 3/4 of a stop and this is gone by F2

Now, unless you post a shot of a completely uniform surface, and use a photo editor, you won;t ever see this in your photos. If this is commented as written above, and that it is not an issue, that should suffice, because there is simply no way to post any kind of interesting shot to show it. lighting will be just too variable.

CA, I agree will be a different issue, specifically lateral CA and the amount of divergence of colors at the edge of the frame, But usually, at least in new lenses, this is pretty limited to about 1-2 pixels wide and easily removed.

11-24-2010, 08:08 AM   #113
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QuoteOriginally posted by Lowell Goudge Quote
the perception I have is that many people like to complain about the reviews but not as many actually contribute for one reason or another.
So true!

I have contributed reviews for every lens I have owned and believe that I have rated them accurately. Truth be known, there are actually very few stinkers out there. Yes, there is a certain amount of "grade inflation" from newbies and fan boys, but in general my expectation would be that any name-brand SLR lens should be at least a 7. If not, I would suspect that it to be a bad copy. Anyone doubting this should take a stroll though the off-brand club thread. In theory the lenses discussed there should be sub-par by definition!


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11-24-2010, 08:09 AM   #114
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QuoteOriginally posted by Lowell Goudge Quote
Out of curiosity, I tested my K50F1.4 and Supertak 50F1.4 (version 1) on all my bodies, and found that all combinations vignette wide open to about 3/4 of a stop and this is gone by F2

Now, unless you post a shot of a completely uniform surface, and use a photo editor, you won;t ever see this in your photos
My concern here is that more novice photographers who realize that this 3/4 of vignetting is a non-issue in real life, will look at the test-shot and conclude that the lens is terrible.

When you show real-world photographs and say "there is some vignetting, as you can see here", photographers of different skill levels can observe the photo and judge the severity of th vignetting for themselves.

I don't think there is anything wrong with photographers stress-testing their gear, but I think it actually is only helpful to the most knowledgeable. For most people, it is very misleading, and can lead one to believe that most gear is outright garbage if you take it all at face value.

At the risk of getting into trouble, I would suggest that this sort of quantification and measurement creates more Rice - High complexes than it does well-tempered lens expertise. (Opinion: Mr. RH is a grade-A dolt). These forums (many photography forums) are rampant with people who read too many graphs, study too many brick walls, and as a result, have a completely unwarranted gear-esteem problem. I think that this lens review database is a wonderful tool for Pentax users, it is completely unique across the entire web. I hope it can be used in a practical way that will be useful to all, instead of those who obsess over specification sheets.

If vignetting is hard to see in real photos because of variable light, why even bother talking about it?
11-24-2010, 08:11 AM   #115
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QuoteOriginally posted by hoojammyflip Quote
There is a Flickr group dedicated to this very task, where you can search for lenses according to their tags.
Beyond that, Flickr is an incredible tool for pre-purchase lens evaluation. Most enthusiasts tag with the lens used and a simple search by the lens name can yield thousands of examples. It was a Flickr search in conjunction with posts by users on this site that sealed my decision to buy my Jupiter-9 some years ago.

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11-24-2010, 08:13 AM   #116
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QuoteOriginally posted by stevebrot Quote
Truth be known, there are actually very few stinkers out there.
I very much agree with this. My absolute worst lens currently has a 4.5 in the database (after I rated it a 7!) The funny thing is, it's not bad at all. It's a takumar bayonet which is supposed to be awful because it does not have SMC coatings. Well that is bullocks. Sure, I can't shoot into the sun, but for the most part is a very useful lens and can hold it's own alongside my 50's (but not the limiteds). It's more than I would expect for a 25 year old bargain bin lens .
11-24-2010, 08:25 AM   #117
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QuoteOriginally posted by paperbag846 Quote
I very much agree with this. My absolute worst lens currently has a 4.5 in the database (after I rated it a 7!) The funny thing is, it's not bad at all. It's a takumar bayonet which is supposed to be awful because it does not have SMC coatings. Well that is bullocks. Sure, I can't shoot into the sun, but for the most part is a very useful lens and can hold it's own alongside my 50's (but not the limiteds). It's more than I would expect for a 25 year old bargain bin lens .
I have often discussed this lens, and yes it has a bad reputation. It is arguably the worst 135 from pentax, but that still makes it better than most 3rd party 135's out there, When People ask about it, I qualify the comments based upon price, for $50 it is not too bad, but if you have an option to any other pentax 135 at an equal price, take the other pentax ofering unless you absolutely need F2.5 vs F3.5.

If you pay more than $50-60 for the Tak bayonet, you paid too much.
11-24-2010, 08:44 AM   #118
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QuoteOriginally posted by Lowell Goudge Quote
If you pay more than $50-60 for the Tak bayonet, you paid too much.
Nope, paid 30 dollars for an 80mm-200mm f4.5 zoom. It is capable of this .

11-24-2010, 08:55 AM   #119
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QuoteOriginally posted by paperbag846 Quote
Nope, paid 30 dollars for an 80mm-200mm f4.5 zoom. It is capable of this .
I wasn't talking about the cigar It looks about the right dimensions.

As commented elsewhere, there are very few real dogs out there. Any lens, under the right circumstances can produce great results.

So maybe, to wrap this thread up, the best way might be to forget the technical points, and even images, and have the reviews discuss the ease or difficulty of using the lens, Yes any lens can take a great shot, but how easy is it to reproduce. Can the lens be a go-to lens where your success rate is better than 50% or is it truely a 1 in a million lens.

Ease of use, limitations of the technical points, such as full or half stops, focusing resistance, focus throw, and how easy to aquire focus, vs precision, how the lens behaves on the camera, are the things that should be stressed more in the ratings, because the technical detail can't be easily measured by users.
It is these observations which are qualitative, and will depend on type of use also, that may be important. THis goes back to my suggestion of a simple checklist, to prompt people to comment even if the comment indicates no issue, it is relevant.
11-24-2010, 09:02 AM   #120
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I like your idea Lowell, but I don't think it would be very useful without some more real-world information. The subjective content of the review is important too.

The reason I posed that picture is because I hear so much bad-mouthing about the Takumar Bayonets. Granted, they are not the best. However, if someone was to only read those opinions, and never see a shot... well they might never give it a chance. A shot like the one above might temper that criticism: "Looks good enough to me". Not everyone will feel that way, but I suppose what I am asking for here is the opportunity for the view to judge for him or her self. Real world images are the best way to do this IMHO, and for a select number to end up in the review section would be very helpful and far from misleading.

It is specifications like "3/4 EV vignetting" that can be misleading. It's better to see those things than to simply read them. Otherwise you might turn someone off of a good lens for their purposes, for no good reason whatsoever other than a compulsion to measure and quantify.
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