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09-26-2012, 08:52 AM   #1
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Older Pentax lens coatings

There has been talk recently about non-digital Tamron and Sigma lenses being somewhat inferior to the upgraded ones (DI and DG respectively) but I haven't seen this discussion for Pentax lenses.

Were the old K, M, A, F and FA lenses somehow better than the 3rd party lenses?
Or are we Pentax users so happy to have old terrific manual lenses available that we don't care?

My hunch would be that the reflections actually don't matter much. Especially if you use a hood.

Seb


Last edited by bassek; 09-26-2012 at 08:52 AM. Reason: spelling
09-26-2012, 09:11 AM   #2
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I think it is a lot like distortion in the audio world, it doesn't take much to get rid of 99% of distortion in an audio system, but that last 1% that the audiophiles crave is expensive.

The old SMC coatings are very good when comparing it to single coated or uncoated glass, any improvement over SMC is just small steps, not a huge leap that is easily noticeable.

The biggest thing about the pre-digital glass is the coating on the rear element, it wasn't necessary to have good coatings on the rear element with film. The digital sensor is reflective, film is not, so on digital you can get ghosting in certain conditions that would not have been a problem on film. I've found this to be an extremely rare occurrence and I have to almost force it to happen.

Last edited by elliott; 09-26-2012 at 09:26 AM.
09-26-2012, 09:26 AM   #3
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So Pentax did put coating on the rear elements too?

Seb
09-26-2012, 09:31 AM   #4
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QuoteOriginally posted by bassek Quote
There has been talk recently about non-digital Tamron and Sigma lenses being somewhat inferior to the upgraded ones (DI and DG respectively) but I haven't seen this discussion for Pentax lenses.

Were the old K, M, A, F and FA lenses somehow better than the 3rd party lenses?
Or are we Pentax users so happy to have old terrific manual lenses available that we don't care?

My hunch would be that the reflections actually don't matter much. Especially if you use a hood.

Seb
Some how, I suspect a previous post I made, has something to do with this. Specifically that Di or DG meant digital as opposed to no designation being a film lens.

Lets look at this carefully as I have lenses from as far back as preset takumars and other 3rd party presets, up to the latest SMC and DG or Di coatings from Pentax Sigma and Tamron

to be clear, pentax has always had excellent coatings compared to the competition, and had multi coatings before the S-M-C takumars, they just did not market it until someone else came out with multi coated lenses as a feature.

SMC coatings have also evolved over time to also include things like resistance to spotting and finger prints etc... so in general, newer lenses have better coarings than older ones. an S-M-C Tak is not the same as and SMC tak is not the same as a K, or M or A etc.....

Next the DG or Di coatings on sigma and tamron, specifically refer to the myth (and I will use this word specifically, because in all my lenses dating back to 1960 I have not seen an issue with reflection off the rear element that has reduced contrast or caused hot spots on the sensor.) that film designed lenses will have problems due to the highly reflective nature of the sensor.

even within the after market lenses newer lenses are probably different coatings than older lenses.

As far as old glass, and why people like it, is many pentax users are cheap. Sorry folks but there is no other way to say it. We use older glass BECAUSE WE CAN.

Personally, when you look at my entire lens collection I have spent more on digital lenses, (i.e. lenses bought brand new from brick and mortar stores either accompanying my DSLRS or to use only with my DSLRs) than I have spent on manual focus lenses. the difference is I have 3 very high quality zooms (Sigma 70-200/2.8, sigma 10-20/4-5.6 and Tamron 28-75/2.8) and 3 recent manual focus primes (Samyang 8mm FE, 14mm/2,8 and 85mm/1,4) than I have spent to aquire all other lenses. In fact my 70-200 cost as much as all 18 M42 lenses i own, ranging from 16mm through 300 mm.

You might ask why I have all the old lenses when i have some excellent new ones. the answer is that the older lenses have some different optical qualities than newer ones. I like the results they produce, and I like to play with them. the new lenses get used as go-to lenses when travelling or doing serious shooting, but when I am "playing at my hobby, i like the old ones.

09-26-2012, 09:32 AM   #5
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QuoteOriginally posted by bassek Quote
So Pentax did put coating on the rear elements too?

Seb
what do you think a D-FA lens is?
09-26-2012, 09:50 AM   #6
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QuoteOriginally posted by Lowell Goudge Quote
what do you think a D-FA lens is?
I have a number of pre-digital Takumar/Pentax lenses. All have coated rear elements, as does the Xenon f2 on my Retina IIIc and the Ultron f2 on my Vitessa L, both of which predate the digital era by decades. Consider: the coatings are probably applied by vacuum deposition. To NOT coat both sides of all elements would really complicated the production process.
09-26-2012, 10:28 AM   #7
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Pentax SMC coating technology has been incremental since its introduction and coating on all surfaces of all elements is the rule. There is a visible difference in the amount of reflection of the older versus the newer lenses (say my Pentax-K SMC vs. my Pentax FA and DA lenses). Some peope put a high degree of importance on the color or the reflection, but this is not good reasoning. My single-coated Jupiter-9 from the early 1960s has a lovely intense purple reflection while my Pentax-FA 35/2 has almost none with very little color!


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09-26-2012, 10:39 AM   #8
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Each lens is going to perform differently. You can't really generalize and say all lenses made before a certain point are going to cause problems with flare and reflections on digital cameras. I have a pretty good sized collection of old glass, some I have owned for years and some found in garage sales along with a few I bought on Ebay and in the Marketplace. Some flare a lot wide open, have bad CA, others don't. One gem was a 28/3.5 Super Tak my sister found in a garage sale and sent it to me. Very little CA at any aperture and incredibly flare resistant, even without a hood. Overall, we are a pretty cheap bunch I suppose. I hate tossing something simply because it's "old". I still own just about all the cameras and gear I have ever bought. Some stuff has been handed down to the kids. I really like being able to use every old lens on my camera. That said, my eyesight ain't what it used to be and I'm buying more and more AF glass as time wears on.

09-26-2012, 11:23 AM   #9
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Apart from the kit lens, the F35-105 is the only one I have purchased new (last year!), all the others are used findings. I really like my F35-70 and can't see any reflections.
What I like are the feel of the K35, M50 and M135. I have recently got the M85 too but I haven't really got to know it yet. We have seen nice shots here on the forum of old lenses, no one have complained of reflections. CA and flare are perhaps easier to spot.

Seb
09-26-2012, 11:32 AM   #10
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QuoteOriginally posted by grhazelton Quote
I have a number of pre-digital Takumar/Pentax lenses. All have coated rear elements, as does the Xenon f2 on my Retina IIIc and the Ultron f2 on my Vitessa L, both of which predate the digital era by decades. Consider: the coatings are probably applied by vacuum deposition. To NOT coat both sides of all elements would really complicated the production process.
I believe the difference is that the coatings are not specifically designed to deal with a highly reflective flat surface, such as the sensor behind the lens. the emulsion layer of the film is simply not shiny.

As I said in my post, the digital designation was to deal with the "myth" of unwanted reflections, I personally in 40 film only lenses have not seen it
09-26-2012, 04:41 PM   #11
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I have seen a purple spot in the exact center of the frame with my Tamron 90mm f2.5 52BB and 52E lenses. It's hard to see at f11 and gets stronger with smaller apertures. I can't say whether this is caused by sensor reflection or some other issue. The lens does have a large rear element that doesn't move when the lens is focused. It's the only lens I've seen with a possible issue.
09-26-2012, 07:58 PM   #12
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QuoteOriginally posted by Just1MoreDave Quote
I have seen a purple spot in the exact center of the frame with my Tamron 90mm f2.5 52BB and 52E lenses. It's hard to see at f11 and gets stronger with smaller apertures. I can't say whether this is caused by sensor reflection or some other issue. The lens does have a large rear element that doesn't move when the lens is focused. It's the only lens I've seen with a possible issue.
My Auto-Rikenon 55/1.4 (M42) also has a large, flat rear element (probably bigger than the sensor!) and often has low contrast that I think may be caused by stray reflections. I suppose I should test it on one of my film cameras


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09-26-2012, 11:21 PM   #13
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QuoteOriginally posted by bassek Quote
Were the old K, M, A, F and FA lenses somehow better than the 3rd party lenses?
Well, the K and M-era lenses were superior optically to nearly all of the 3rd party K-mount alternatives, in pretty much all optical aspects. The best coatings at this time (and this probably endures to this day) were Pentax's SMC and Nikon's NIC.

I ssem to remember that, optically, the best 3rd party alternatives were probably from Tokina and Tamron, and certain Vivitars. Cosina and Ricoh made some decent K-mount lenses, but I'm not counting these as "3rd party".
09-27-2012, 03:28 AM   #14
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QuoteOriginally posted by Just1MoreDave Quote
I have seen a purple spot in the exact center of the frame with my Tamron 90mm f2.5 52BB and 52E lenses. It's hard to see at f11 and gets stronger with smaller apertures. I can't say whether this is caused by sensor reflection or some other issue. The lens does have a large rear element that doesn't move when the lens is focused. It's the only lens I've seen with a possible issue.
I should check my 52BB. What body and shooting setup produced the spot, I could try to replicate on my kit and see if it is a lens issue or wat
09-27-2012, 08:10 PM   #15
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QuoteOriginally posted by Lowell Goudge Quote
I should check my 52BB. What body and shooting setup produced the spot, I could try to replicate on my kit and see if it is a lens issue or wat
I guess I deleted the photos. I set up a tripod maybe five feet from a white wall, focused on the wall, chose an exposure for a histogram that was to the right, and took shots at different stops. From memory, I could see something at f11, more obvious at f22. In real-world photos, I didn't see it without a subject that would make it obvious or aggressive processing techniques like boosting saturation. I tried to add some shielding to the rear element on the theory that the Adaptall mount was not optimized for stray light, with no result. When I got the model 52E, same optically, its mount is more shielded. I did the same test and had the same spot. I have since sold the 52BB, mentioning the spot in the ad, and the buyer was happy . I can duplicate the test when I have more time. The lens reviews say something similar about the spot.
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