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09-28-2009, 05:44 PM   #1
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Multi coatings & CA Query

Hey guys,

Just purchased an old M42 Tak 300mm F4 preset aperture lense from ebay - non coated afaik.

I'm curious if I were to use my KENKO 2x Teleplus MC7 coated teleconverter would that help remove some of the CA that I'm bound to find with this thing?

Cheers.

09-28-2009, 05:57 PM   #2
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it would be more likely that the TC would ADD to the CA already present. though I have heard of cases where adding a multicoated filter to a lens can help improve it's characteristics
09-28-2009, 05:58 PM   #3
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You might be suprised, some of the old lenses perform very well. It might not have much CA. If you do get CA you can remove some of it in post processing. Apple Aperture has a way to remove it. I'm sure Lightroom does too.
09-28-2009, 06:01 PM   #4
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From the tests i've seen of this lens it's a tiny bit soft but pretty good @ F4.0 good from 5.6 up to F11 or so. It's the one with quite harsh bokeh I think I'll have to post up some photos when it arrives.

However it does display significant CA, based off some photos i've seen in bright light compared to an older Nikkor 300mm ~F4


I still cant wait for it

09-28-2009, 06:07 PM   #5
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By the same token, can you get a multicoated lens filter that will protect the front element and also reduce CA?

Recommendations welcome, 77mm filters!

** Also, is the old rubber ring F4 300mm tak that I have (model II) coated at all? single maybe?
09-28-2009, 10:42 PM   #6
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Hey Fuitloops,

77mm is a large size for filters. For my single coated lenses I experiment and try good Skylight 1A, Skylight 1B and Multi-Coated UV filters. There is a lot of variation in coatings and glass formulations so the filters will have different effects on the lenses. Just get out there and experiment!

A decent Multi-Coated UV filter is the Pro 1 by Hoya, they have eight layer coatings on each side. For 77mm it might get a little pricey. I would check eBay to see if there are any good deals.

The 300mm Takumar, is it marked Super Multi Coated or abbreviated SMC? Some late model Super-Takumars were multicoated without being marked as such. Pentax also sold a discount line of lenses called Takumars which were not multicoated. Post a picture of your lens so we can see what we are talking about.

Last edited by Angevinn; 09-29-2009 at 08:20 AM.
09-29-2009, 01:02 AM   #7
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If it got the rubber focus ring and is m42 it is a S-M-C Takumar and is multicoated.
09-29-2009, 01:46 PM   #8
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In theory, coating shouldn't really have anything to do with chromatic aberration.

CA results from the refractive characteristics of the glass itself. Refraction affects different wavelengths (colors) of light different amounts; this phenomenon is called "dispersion," and it tends to spread white light into a spectrum like a prism. This is the CA you see. Both refraction and dispersion result from the speed of light being slower in materials (glass, water, or whatever) than it is in air or vacuum.

Regardless of the coating, that effect takes place within the glass.

More modern lenses use complementary lens materials that attempt to bend the light back so the colors line up again -- one element is designed to compensate for another element's CA.

It's somewhat of a coincidence that modern lenses have (a) better CA characteristics, as a result of better materials, and (b) better coatings. What I mean is, it is absolutely true that newer lenses have both better CA characteristics and better coatings. But one isn't the result of the other; they just improved in more or less the same timeframe.

So I wouldn't expect putting a multicoated filter on a lens to have any effect at all on chromatic aberration.

I don't know if there's a definite answer on the teleconverter, though. There is a possibility that your teleconverter just happens to cancel out your lens's CA, but I'd consider that highly unlikely. In most cases, I'd expect CA to be the same or worse.

09-29-2009, 01:57 PM   #9
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As said above, coating doesn't have to do with CA, it has to do with contrast and flare.

As for CA, how easily it can be corrected depends on if it is longitudinal or lateral:
Chromatic aberrations
09-29-2009, 02:34 PM   #10
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+1 +1 +1 to the above.

Even the preset Takumars are coated, just not super multi coated.

Some of the older lenses actually are pretty good re. CA, given simpler designs etc. Some aren't - I don't know about this particular one.

The way I think of this - CA + light bloom aka veiling flare = more noticeable smearing in the photo itself.

Filters don't fix either thing - and a hood won't either, when the source of the CA and light bloom is in the frame itself. Theoretically, that is. A given combo may result in the final result being an improvement.
09-29-2009, 02:42 PM   #11
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"Uncoated" 300mm f4 Takumar

To my knowledge ALL Takumars are coated, but not all are multicoated. I have my father's Asahiflex IIa, made in the mid 1950's, and lenses for it, (37mm screw thread mount, BTW) the 50mm f3.5, a 35mm f2.8 (I think that is the speed) and the 83mm f1.9. ALL are coated, as evidenced by the purplish cast to the lens surfaces when viewed at an angle. Lens coating is common for post WWII cameras. My Retina IIIc has a coated f2 Xenon, and dates to about 1956 or 1957.

I wouldn't be afraid of "single coated" lenses. I have a Takumar 135mm f2.5 K mount which is a respectable performer. It has a good built in lens hood and, after all, with a SLR we can SEE flare, and decide if its objectionable.

Uncoated lenses are uncommon in this day and age, unless you go for collectibles, old Leicas and Contaxes, and that sort.
09-29-2009, 06:11 PM   #12
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Excellent info guys, thanks!

I got confused with all the talk of the Super taks, SMC taks and their coating and reviews of an older regular takumar which showed some pretty serious CA from what I have seen in some scenarios. I put two and two together, and incorrectly thought it was the coatings. I knew coatings reduced flare and not CA. Correlation is not causation however so doh, I fail.

I am pleased to hear it has a single coating, I had thought the Super tak referenced to it being coated but it actually represents a different more modern aperture design and different optical configuration compared to the preset 18 blade aperture version. I am hoping the harsh bokeh photos I saw were not from the 18 bladed design, i'll see once it arrives and I get some test shots done.

Once I have the lens in my hand I would've noticed the color cast from the coating, but it hasn't arrived yet.

Speaking of coatings, If I had an Pentax-M SMC 50mm F1.7 would a diluted solution of vinegar damage the coating for removing fungus from an internal element?

Last edited by FruitLooPs; 09-29-2009 at 06:19 PM.
09-30-2009, 01:44 AM   #13
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QuoteOriginally posted by FruitLooPs Quote
Speaking of coatings, If I had an Pentax-M SMC 50mm F1.7 would a diluted solution of vinegar damage the coating for removing fungus from an internal element?
I don't see hy vinegar would damage the fungus.
09-30-2009, 12:40 PM   #14
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QuoteOriginally posted by FruitLooPs Quote
Speaking of coatings, If I had an Pentax-M SMC 50mm F1.7 would a diluted solution of vinegar damage the coating for removing fungus from an internal element?
Most modern lens coatings are made from materials like Magnesium Oxide which will not be disolved by anything you can easily get hold of unless you work in a lab. They can be damaged quite easily by abresion as they are very thin (each coating may be in the region of 1/10000 mm thick). I have used household methilated spitits to remove fungus and have not had any problems. Vinegar may work but I have not tried it. I doubt that it will remove the coatings unless applied with sandpaper though.
10-12-2009, 12:16 AM   #15
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Photo examples

So i've had my mits on the lens for a week now. Pretty pleased with it overall.

2x Kenko MC7 t/c is softer than cropping without it.

Took it too the zoo handheld with K20D pretty heavy combo to carry for hours!

https://www.pentaxforums.com/forums/post-your-photos/76198-nature-day-zoo.html

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