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Pentax 35/4.0 for UV

UV Lens
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#1 Andrea B.

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Posted 17 April 2015 - 19:58

I've mentioned this lens before and shown some work from it. Yesterday when I was out testing the Kaligar 35/3.5, I also ran the tests on this Pentax lens. Yes, this is a 4.0 lens.
EDIT: The lens is marked "Asahi Opt. Co.".

I think I like the Kaligar a little better for UV. The Kaligar 35 may be have a touch more microcontrast contrasty and sharper than the Pentax 35 in the PEF, but nothing that editing couldn't fix for the Pentax 35. (Which, by the way, I may not have completely accomplished in these renditions. It takes a while to learn how best to edit a camera/lens combo, she pleaded.) In the fence photo the Kaligar had the faster UV exposure time, but in the flower shot the Pentax won. The Pentax has slightly harsher background bokeh at f/11? (Or there could be a dust mote in the bokeh?) It might be a better f/8 lens.

EDIT: I should not have used the phrase "contrasty and sharper" above because I was referring to microcontrast. Older lenses may not always have the microcontrast which comes from improved coatings. However, as mentioned, microcontrast may be tweaked in Photoshop or another app.

Equipment: Pentax K5-broadband + Pentax 35/4.0 + Sunlight
Filters: Baader UV/IR-Cut, BaaderU UV-Pass, B+W 093 IR-Pass
Exposure: f/11 and ISO-160 (base ISO on the K5).

Colour and white balance were freshly profiled for this test.

Click up these 1200 pix crops in an expanded browser for the best look at what this lens can do.

Set 1: Glory-of-the-Snow Flowers at about 3 feet.

Visible [f/11 for 1/160" @ ISO-160]
Attached Image: testLens_pentax35-4.0_k5_visSun_f11_1-160_iso160_20151504wf_131800pn.jpg

Ultraviolet [f/11 for 2" @ ISO-160]
Attached Image: testLens_pentax35-4.0_k5_uvBaadSun_f11_2_iso400_20151504wf_132113pn.jpg

Infrared [f/11 for 1/125" @ ISO-160]
Attached Image: testLens_pentax35-4.0_k5_093IrSun_f11_1-125_iso400_20151504wf_132519pn.jpg


Set 2: Fence at about 20 feet, maybe?

Visible [f/11 for 1/80" @ ISO-160]
Attached Image: testLens_pentax35-4.0_k5_visSun_f11_1-80_iso160_20151504wf_140000pn.jpg

Ultraviolet [f/11 for 4" @ ISO-160]
There is some background jitter in the tree branches from the wind which was gusty at times. Not a fault of the lens, of course.
Attached Image: testLens_pentax35-4.0_k5_uvBaadSun_f11_4_iso160_20151504wf_140201pn.jpg

Infrared [f/11 for 1/30" @ ISO-160]
Attached Image: testLens_pentax35-4.0_k5_093IrSun_f11_1-30_iso160_20151504wf_140342pn.jpg


Set 3: CCPassport & Standards

Attached Image: lensTest_pentax35-4.0_k5_visSun_f11ss1-250_iso160_20151604wf_134751pn.jpg

Attached Image: lensTest_pentax35-4.0_k5_uvBaadSun_f11ss2.5_iso160_20151604wf_134953pn.jpg
Andrea G. Blum
Often found hanging out with flowers & bees.

#2 OlDoinyo

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Posted 23 April 2015 - 20:10

If this 35/4 is the one I am thinking of, I have one too. I did not purchase it for invisible work; rather it was a stopgap fix to plug a hole in my collection while I searched for the rarer Minolta 35/2 (which I eventually got.) It actually appears in one of Dr Schmitt's performance tables, as it turns out, rated about to 345 nm. All of my SD14 UV shots were taken with this lens, some of which you have seen on this site.

Some lenses in this series used thoriated glass, which is mildly radioactive and slowly turns yellow over time. However, the 35/4 is not specifically listed as one of these.

#3 Andrea B.

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Posted 23 April 2015 - 21:46

Interesting about the thoriated glass! Mine does not appear to have any yellowing.
I'm not sure the 35/4 is considered 'rare', but I do not often see them for sale.
Andrea G. Blum
Often found hanging out with flowers & bees.

#4 Andrea B.

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Posted 19 May 2019 - 18:41

Minor edit above: I rephrased a comment about contrast/sharpness in the first post.
Andrea G. Blum
Often found hanging out with flowers & bees.