[jsherman999]

I haven't used mt 135mm f/3.5 that I bought off you ages ago ... but I do have some online shots from it ... it is a wonderful lens ... even in the middle of the day in bright sunlight ... I found it is one of the better lenses on the K10D for exposure as well (nearly all shots were spot on from what I could see).

Its amazing what LBA can do - I've sold two Tak 135's in the past year...

Yet I bought 4. So I currently have two. (local store here sometimes gets in a mess
of lenses when someone brings in their dad's old pentax stuff to sell, and whenever
I see and hold a nice Tak, well.... you know the feeling.)

And those shots are awesome, especially the 2nd and horse. I'd like to see the first larger.




.

[gokenin]

Its amazing what LBA can do - I've sold two Tak 135's in the past year...

Yet I bought 4. So I currently have two. (local store here sometimes gets in a mess
of lenses when someone brings in their dad's old pentax stuff to sell, and whenever
I see and hold a nice Tak, well.... you know the feeling.)



.

Hey if you ever manage to snag a Tak in the 20-28 range at that store would you keep an eye out for me I have nowhere near me that resells pentax lens and that only leaves the marketplace or ebay for me

[Mechan1k]

Jay ... here's the link to that first image ... although i am not sure if Zenfolio will allows other users view it.

http://mechan1k.zenfolio.com/img/v4/p920272695.jpg

If it works that's cool.

I do remember the 135mm having such a well damn focus ring on it ... it was very nice to hold and use.

[JonPB]

I don't think the test setup is actually that condusive to testing lens flare. I think you're actually looking more at "blooming" which to my understanding is more to do with optical design than coatings.

Admittedly, I was using the broadest possible definition of flare: light misdirected by the lens onto the sensor. I have never formally studied optics, but my understanding is that there are two kinds of misdirection, which I will call reflection and scatter. The difference is between light hitting a mirror and reflecting back or hitting a white wall and scattering in every direction.

Most of the light reflecting off of a lens will exit back out of the lens, but some of that will reflect for a second time back into the lens and create a ghost--this is how those series of light discs appear in an image like the one you posted, Bradley, and is probably what most people think of when they hear "lens flare."

On the other hand, light can hit a lens and just scatter; much of that scattered light won't be reflected at all and will just continue on to the sensor in a diffracted wave rather than a beam, and some of that light will be scattered out of the lens and then reflected back at the sensor. Either way, the result is a more diffuse and indiscriminate brightening of the image. This is the sort of problem that lens hoods prevent, and may well be better called "blooming" to distinguish it from proper flare.

Naturally, having more surfaces in a lens--groups and elements--will provide more opportunities for light to reflect and scatter. But these lenses aren't all that different: I believe the 105 is a 4-4 groups-elements, therefore with eight surfaces; the S-T 135s are 4-5, with nine or ten surfaces; and the 135M is 5-5, with ten surfaces. There is going to be some difference between an eight-surface and a ten-surface lens, but the amount of that difference depends entirely on how well each lens avoids reflecting and scattering light.

SMC is supposedly good for a light transmission of 99.8%. I have no idea what the coefficient of refraction is on other lenses. If SMC is staggeringly better than other coatings, then the type of coating means more than the optical design of the lens. But if the coatings are equivalent then the number of reflective surfaces is the most important issue.

My guess is that different coatings treat reflection and scatter differently: some are better at reducing one than the other. I wouldn't be surprised if it is easier to decrease reflection than to increase transmission, meaning that scatter--bloom--is effectively increased.

If I were to hazard another guess, the main reason zoom lenses didn't catch on until the 1970's or so is because of coatings. A fourteen element lens is going to have huge problems with reflection and scatter unless the coatings are excellent. But for simple designs, like prime lenses, uncoated glass can do respectably well.

If there's a good reference for understanding this sort of thing, I would greatly appreciate a link. Optics have been fascinating me lately.

[d.bradley]

Admittedly, I was using the broadest possible definition of flare: light misdirected by the lens onto the sensor. I have never formally studied optics, but my understanding is that there are two kinds of misdirection, which I will call reflection and scatter. The difference is between light hitting a mirror and reflecting back or hitting a white wall and scattering in every direction.

Most of the light reflecting off of a lens will exit back out of the lens, but some of that will reflect for a second time back into the lens and create a ghost--this is how those series of light discs appear in an image like the one you posted, Bradley, and is probably what most people think of when they hear "lens flare."

On the other hand, light can hit a lens and just scatter; much of that scattered light won't be reflected at all and will just continue on to the sensor in a diffracted wave rather than a beam, and some of that light will be scattered out of the lens and then reflected back at the sensor. Either way, the result is a more diffuse and indiscriminate brightening of the image. This is the sort of problem that lens hoods prevent, and may well be better called "blooming" to distinguish it from proper flare.

Naturally, having more surfaces in a lens--groups and elements--will provide more opportunities for light to reflect and scatter. But these lenses aren't all that different: I believe the 105 is a 4-4 groups-elements, therefore with eight surfaces; the S-T 135s are 4-5, with nine or ten surfaces; and the 135M is 5-5, with ten surfaces. There is going to be some difference between an eight-surface and a ten-surface lens, but the amount of that difference depends entirely on how well each lens avoids reflecting and scattering light.

SMC is supposedly good for a light transmission of 99.8%. I have no idea what the coefficient of refraction is on other lenses. If SMC is staggeringly better than other coatings, then the type of coating means more than the optical design of the lens. But if the coatings are equivalent then the number of reflective surfaces is the most important issue.

My guess is that different coatings treat reflection and scatter differently: some are better at reducing one than the other. I wouldn't be surprised if it is easier to decrease reflection than to increase transmission, meaning that scatter--bloom--is effectively increased.

If I were to hazard another guess, the main reason zoom lenses didn't catch on until the 1970's or so is because of coatings. A fourteen element lens is going to have huge problems with reflection and scatter unless the coatings are excellent. But for simple designs, like prime lenses, uncoated glass can do respectably well.

If there's a good reference for understanding this sort of thing, I would greatly appreciate a link. Optics have been fascinating me lately.

My understanding of "flare" as you have described it here is different from the blooming I refer to. The artifacts I showed in my photo were indeed flare, but so too is what you describe as the "diffuse and general brightening". My understanding is that that kind of flare is the same as the kind in my photo, but dispersed over a larger area...sometimes the whole frame. This occurs with light coming in from oblique and hitting the lens surfaces, and from my basic understanding of optics (please correct me if I'm wrong) the flare is from a kind of (internal) reflection.

The blooming I refer to (and what you measured in the initial post) is actually still "flare" but caused by scattering, not reflection. See the shoulder of her white jersey? This was shot with the SMC Takumar 35/2 wide open.



So yes...both are flare, but my understanding is that coatings are more apt to reduce internal reflections rather than the scattering you measured. The scattering is a product of optical design rather than coatings. Again...this is my understanding, all corrections welcome.

[chse]

Admittedly, I was using the broadest possible definition of flare: light misdirected by the lens onto the sensor. I have never formally studied optics, but my understanding is that there are two kinds of misdirection, which I will call reflection and scatter. The difference is between light hitting a mirror and reflecting back or hitting a white wall and scattering in every direction.

I had an eye opening experience when I used a super Takumar 35mm/2 for night pictures. The whole image had little contrast and real blacks were missing. I do not have a SMC 35/2 for comparison but all other smc lenses and a Tamron 24/2.5 I have were much better. I think flare shows here easily since there were a lot of small light sources in the images. Maybe give it a try with your lenses.

[JonPB]

The blooming I refer to (and what you measured in the initial post) is actually still "flare" but caused by scattering, not reflection.

You point out a kind of noise I hadn't noticed before, which is, I believe, what chse is talking about as well: a strong point of light appears to bleed, or bloom, into areas of dark around it. And seeing as how sharp contrasts help make strong images, this can be a problem.

I had an eye opening experience when I used a super Takumar 35mm/2 for night pictures. <snip> I think flare shows here easily since there were a lot of small light sources in the images. Maybe give it a try with your lenses.

If I have a good opportunity to, I will. The only fast lens I have is a A50/1.7, so that's what I've been using for walking around at night. I have an Auto-Tak 55/1.8 on the way so I can set up a comparison. If I do that, I'll also throw in the DA18-55 to see if it is any different in this regard from the A series.

[JonPB]

Here's Imatest's page on testing for lens flare, which they call veiling glare. I trust them to know the best way to test such things, and they recommend building a contraption. If there's enough interest in this, I'd be happy to build one and test the lenses I have for the common good... otherwise, I think I'll just be out taking pictures.

Here's Ken Rockwell's page on lens sharpness, which I find interesting and is related to this thread as it pertains to lens testing.

And here's what I consider to be conclusive proof that my two Super-Tak 135's have different coatings. In the first image, my 3,0xx,xxx is on the upper-left; in the second, on the upper-right. The other is the 3,7xx,xxx. Notice how different the reflections of the lightbulb are, despite the light being constant between the two pictures.

These images also show that neither Super Tak has anything on SMC coating, as demonstrated by the M135 in the lower-left, but are both better than the Tak 105's coating.



Closer up:

[Zewrak]

As fun as it is to compare these lenses. I have come to the conclusion that you will never get a proper answer. I have tested alot of different of these lenses. They simply all have personality. Just as the topic starter states, there are small differences between each and every lens, making them perform differently. Subtle and with personality. I have had a total of four Super Takumar 135mm. All four of them was different and gave me different results. All of them were/are great lenses. But there are small differences.

My advice in all this is, get one of them that you like and stick with it. There will always be better or worse out there. Just get one that fits you.

My personal list of taste:

Auto Takumar 85/1.8 beats Super Takumar 85/1.9.
Takumar 105/2.8 beats Super Takumar 105/2.8
SMC-M 200/4 beats Super Takumar 200/4
Super Takumar 135/3.5 beats SMC-M 135/3.5
S-M-C Takumar 135/3.5 beats Super Takumar 135/3.5
Super Takumar 35/3.5 beats SMC-M 35/3.5
SMC-M 28/3.5 beats Super Takumar 28/3.5