K-1 IR lens hotspot thread

MJKoski · 06-04-2019, 10:30 AM

It seems Zeiss 25mm f/2.8 or f/2 might be good option. Any experience with FA 35/2 lens? HD-version is available as new but again no idea if the new coating works with IR or not :/ Stock K-1 mk2 is not as bad as one might think - it has few tricks in its sleeve. Cranking up ISO all the way to 800k+ and turning screen brightness to maximum gives usable composition even after the sunset. But, sure, it does not help with long exposure times.

MJKoski · 06-04-2019, 03:19 PM

I decided to try my luck with FA28mm 2.8 AL next and found a used one. I am returning the 31mm Limited lens as it has lens wobble issue. Not the fault of the lens but the shop instead which sold it "in perfect condition".

**pcrichmond** · 06-04-2019, 08:14 PM - **1 Like**

I use both full spectrum K-01 and K1. Generally use hoya r72, tiffen 87, lee 87c and albinar 850 plus sometimes an old F29. Just picked up an IR Chrome from Kolari tht I'm axious to try my next free day.
Lenses I've tested in my collection so far:
Sigma 18-50/2.8 DC macro extreme hot spot
Sigma 24-60 DG extreme hot spot
Sigma 70-200/2.8 DG HSM/OS extreme hotspot
Tamron 90/2.8 SP macro (72E) very extreme hot spot almost non useable
Tokina 400/5.6 SD no hot spot
Sigma 24/2.8 super wide no hot spot
Pentax M200/4, M100/4 macro, A50/2.8 Macro, M50/1.7. K30/2.8, A35/2.8, FA135/2.8, FA300/4.5, F35-70/3.5-4.5, F80-200/4.7-5.6, DA 15/4, DA 70/2.4, DA 18-55/3.5-5.6 ALII no hot spots
Vivitar PKA 28 & 35 no hot spot
Lensbaby Plastic optic, soft focus optic, twist 60 (love this one for IR), edge 80 & sweet 35 no hot spot
Plus several enlarger lens conversion with no hot spot.
Kiron 28-105/3.2-4.5 slight hotspot but still useable
Beautiful phots posted so far. Nice to see others enjoying IR.

MJKoski · 06-04-2019, 11:48 PM

Thank you for the looong list

**pcrichmond** · 06-05-2019, 08:09 AM

Yea, it is long. I tend to test every lens I have to find my solid performers.
I had heard the theory @Bob256 mentions and have been curious if this is the case as I've noticed all my current digital era Sigmas hot spot yet the film era 24mm does not.
My digital era Pentax don't and the film era Tamron does..
Would be interesting to find out somehow if the coating material used by each manufacture is indeed more IR reflective and to what degree, but probably proprietary knowledge there.
I like his idea of testing on a wall with dedicated IR light. I do a pinhole test for UV transmission with dedicated light so might try to find an artificial IR source and give his test a try.
Trial and error works fine and I have enough lenses I don't need to feed LBA for dedicated IR lenses but curios if IR wavelengths are more prone to reflectance from coating material and lens barrel design or is it a defined ghosting effect between sensor and filter or combination of both?

MJKoski · 06-05-2019, 08:43 AM

My quality filter, Heliopan, just arrived. Gonna pick it up tomorrow and stuff right onto Samyang 35mm.

MJKoski · 06-06-2019, 01:26 AM

Hmm. Okay. This Heliopan RG780 (digital slim) is optically different (not just the cut-off point) to Hoya R72. R72 gives a clear hotspot at f/4 with 35mm Samyang. Heliopan reaches the same intensity at f/8 and flares a quite a LOT less. Now I can use the Samyang @ f/5.6 compared to f/2.8 or so with R72.

MJKoski · 06-06-2019, 09:14 AM - **1 Like**

Pentax FA28mm f/2.8 SUCCESS. This is priceless. No hotspot even stopped down to f/16. And this is sharp copy. Cheapest wide angle I have tested for IR and the only one that worked.

FA28mm AL @ F/8 and 120 seconds. Biggest Tombstone in Finland. Neewer 850nm IR Filter and channel swap in Photoshop.

**pcrichmond** · 06-06-2019, 07:50 PM

Congrates on the new filter. I've heard Heliopan are good quality though haven't tried them myself. The 780 should be about the same cutoff and 50% transmission as the old Kodak 87, which is still my favorite bandpass to work with. Wonder if any one has researched if hot-spotting is more prone to the amount of visible or near IR a filter lets pass?
Great shot with the FA28. Imagine it should be a solid performer, haven't found many film era Pentax lenses that have IR issues.

Medex · 06-07-2019, 03:39 AM - **1 Like**

Originally posted by MJKoski

Pentax FA28mm f/2.8 SUCCESS. This is priceless. No hotspot even stopped down to f/16. And this is sharp copy. Cheapest wide angle I have tested for IR and the only one that worked.

FA28mm AL @ F/8 and 120 seconds. Biggest Tombstone in Finland. Neewer 850nm IR Filter and channel swap in Photoshop.

Yeap, you really need converted camera to get not blurry folliage.
Today I get my second K-1 body (used 22000 shutter count). I think I will convert my older one (73000 shutter count) to infrared camera. I would like to install 665 nm filter from Thorlab. It is just a question they could make custom dimensions filter. Still waiting for the answer. Their standard is 50.4x50.4 mm x2 mm thickness.
Some examples from Pentax K-5, 640 nm filter (postprocessed)

MJKoski · 06-07-2019, 08:07 AM

I picked 720nm converted Fuji X-A3 from ebay. Safe option to start a "new hobby". Pentax glass fits with adapter.

**travelswsage** · 07-06-2019, 08:41 AM - **2 Likes**

Hope we can keep this thread running. How is the Fuji x-a3 working out?

Got a chance yesterday to go out and shoot and can add the Zeiss zk 35mm and zeiss leitaxed zf 135mm as working without hotspots -- one from each attached. I've also had good luck with the zeiss zk 25mm 2.8 and the Pentax dfa 28-105 (only tried at the wide end so far). These are on the K-1 with the Hoya R-72 filter.

**pcrichmond** · 07-06-2019, 07:33 PM

Nice to see the Zeiss handle so well.
I picked up a MOG Diaplan projection lens from here on the forums to see how the longer triplet would work for UV.
No hot spots in IR either for that one.

zapp · 07-07-2019, 06:23 AM

Zeiss sells their lenses also as an industrial line with extended spectral range. I would expect all of them to perform well, even with regular coatings.

**travelswsage** · 10-01-2019, 06:13 PM

I finally took the plunge and picked up a used sony a7rii and had Kolari convert to dual spectrum. Got a chance to test a bunch of lenses today and was pretty disappointed with most of the results. Used an 850nm external filter and Fotodiox adapters for the lenses. I didn't take notes as well as I should and I had to control the aperture with the novoflex adapters. Used 1 or 2 step up rings to get to 77mm filter size -- I'm not sure but I don't think this should impact quality except that I could not use a lens hood to help with flare.

The good:
Pentax 67 120mm. Best of all lenses tested (unfortunately, also the least useful lens). No hotspot at any aperture, not even at F32.

Pentax 67 100mm. Good through F16. Hotspot appears at F22.

The not so good:
Zeiss ZK 25mm 2.8 Ok to 5.6, F8 useable.

Zeiss ZK 35mm 2 similar to 25mm.

Pentax DFA 28-105 Extremely flare prone, to the extent that it was difficult to tell what was flare and what was hotspot. Ok to 5.6 at most focal lengths. Not so good after.

Lensbaby 56 Ok to F8. Increasing hotspot thereafter.

Pentax DFA 100 macro; Ok to 5.6 or 8; increasing hotspot thereafter

The ugly:
DFA 70-210 2.8. Tested at 70mm, 100mm, 150mm. Generally only good wide open, some lightness at F4 and not really useable after that. This and the Sigma are real disappointments.

Sigma 180 3.5 macro Ok to 5.6. Distinct hotspot thereafter.

I have a couple of others yet to test but am waiting on some step up rings to arrive. If anyone has experience using any of these on a converted K-1 I'd be interested in hearing ...

06-04-2019, 08:14 PM - 1 Like	#18
pcrichmond Site Supporter Join Date: Sep 2014 Location: Bishop, CA Posts: 278	I use both full spectrum K-01 and K1. Generally use hoya r72, tiffen 87, lee 87c and albinar 850 plus sometimes an old F29. Just picked up an IR Chrome from Kolari tht I'm axious to try my next free day. Lenses I've tested in my collection so far: Sigma 18-50/2.8 DC macro extreme hot spot Sigma 24-60 DG extreme hot spot Sigma 70-200/2.8 DG HSM/OS extreme hotspot Tamron 90/2.8 SP macro (72E) very extreme hot spot almost non useable Tokina 400/5.6 SD no hot spot Sigma 24/2.8 super wide no hot spot Pentax M200/4, M100/4 macro, A50/2.8 Macro, M50/1.7. K30/2.8, A35/2.8, FA135/2.8, FA300/4.5, F35-70/3.5-4.5, F80-200/4.7-5.6, DA 15/4, DA 70/2.4, DA 18-55/3.5-5.6 ALII no hot spots Vivitar PKA 28 & 35 no hot spot Lensbaby Plastic optic, soft focus optic, twist 60 (love this one for IR), edge 80 & sweet 35 no hot spot Plus several enlarger lens conversion with no hot spot. Kiron 28-105/3.2-4.5 slight hotspot but still useable Beautiful phots posted so far. Nice to see others enjoying IR. Last edited by pcrichmond; 06-04-2019 at 08:30 PM. Reason: forgot item

06-06-2019, 09:14 AM - 1 Like	#23
MJKoski Veteran Member Join Date: Aug 2016 Posts: 1,784 Original Poster	Pentax FA28mm f/2.8 SUCCESS. This is priceless. No hotspot even stopped down to f/16. And this is sharp copy. Cheapest wide angle I have tested for IR and the only one that worked. FA28mm AL @ F/8 and 120 seconds. Biggest Tombstone in Finland. Neewer 850nm IR Filter and channel swap in Photoshop. Last edited by MJKoski; 06-06-2019 at 11:58 AM.

07-06-2019, 08:41 AM - 2 Likes	#27
travelswsage Site Supporter Join Date: Jun 2016 Posts: 385	Hope we can keep this thread running. How is the Fuji x-a3 working out? Got a chance yesterday to go out and shoot and can add the Zeiss zk 35mm and zeiss leitaxed zf 135mm as working without hotspots -- one from each attached. I've also had good luck with the zeiss zk 25mm 2.8 and the Pentax dfa 28-105 (only tried at the wide end so far). These are on the K-1 with the Hoya R-72 filter. Last edited by travelswsage; 05-18-2020 at 09:39 AM.

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06-04-2019, 10:30 AM	#16
MJKoski Veteran Member Join Date: Aug 2016 Posts: 1,784 Original Poster	It seems Zeiss 25mm f/2.8 or f/2 might be good option. Any experience with FA 35/2 lens? HD-version is available as new but again no idea if the new coating works with IR or not :/ Stock K-1 mk2 is not as bad as one might think - it has few tricks in its sleeve. Cranking up ISO all the way to 800k+ and turning screen brightness to maximum gives usable composition even after the sunset. But, sure, it does not help with long exposure times.

06-04-2019, 03:19 PM	#17
MJKoski Veteran Member Join Date: Aug 2016 Posts: 1,784 Original Poster	I decided to try my luck with FA28mm 2.8 AL next and found a used one. I am returning the 31mm Limited lens as it has lens wobble issue. Not the fault of the lens but the shop instead which sold it "in perfect condition".

06-04-2019, 11:48 PM	#19
MJKoski Veteran Member Join Date: Aug 2016 Posts: 1,784 Original Poster	Thank you for the looong list

06-05-2019, 08:09 AM	#20
pcrichmond Site Supporter Join Date: Sep 2014 Location: Bishop, CA Posts: 278	Yea, it is long. I tend to test every lens I have to find my solid performers. I had heard the theory @Bob256 mentions and have been curious if this is the case as I've noticed all my current digital era Sigmas hot spot yet the film era 24mm does not. My digital era Pentax don't and the film era Tamron does.. Would be interesting to find out somehow if the coating material used by each manufacture is indeed more IR reflective and to what degree, but probably proprietary knowledge there. I like his idea of testing on a wall with dedicated IR light. I do a pinhole test for UV transmission with dedicated light so might try to find an artificial IR source and give his test a try. Trial and error works fine and I have enough lenses I don't need to feed LBA for dedicated IR lenses but curios if IR wavelengths are more prone to reflectance from coating material and lens barrel design or is it a defined ghosting effect between sensor and filter or combination of both?

06-05-2019, 08:43 AM	#21
MJKoski Veteran Member Join Date: Aug 2016 Posts: 1,784 Original Poster	My quality filter, Heliopan, just arrived. Gonna pick it up tomorrow and stuff right onto Samyang 35mm.

06-06-2019, 01:26 AM	#22
MJKoski Veteran Member Join Date: Aug 2016 Posts: 1,784 Original Poster	Hmm. Okay. This Heliopan RG780 (digital slim) is optically different (not just the cut-off point) to Hoya R72. R72 gives a clear hotspot at f/4 with 35mm Samyang. Heliopan reaches the same intensity at f/8 and flares a quite a LOT less. Now I can use the Samyang @ f/5.6 compared to f/2.8 or so with R72.

06-06-2019, 07:50 PM	#24
pcrichmond Site Supporter Join Date: Sep 2014 Location: Bishop, CA Posts: 278	Congrates on the new filter. I've heard Heliopan are good quality though haven't tried them myself. The 780 should be about the same cutoff and 50% transmission as the old Kodak 87, which is still my favorite bandpass to work with. Wonder if any one has researched if hot-spotting is more prone to the amount of visible or near IR a filter lets pass? Great shot with the FA28. Imagine it should be a solid performer, haven't found many film era Pentax lenses that have IR issues.

06-07-2019, 03:39 AM - 1 Like	#25
Medex Pentaxian Join Date: May 2013 Location: Vilnius Posts: 1,020	Originally posted by MJKoski Pentax FA28mm f/2.8 SUCCESS. This is priceless. No hotspot even stopped down to f/16. And this is sharp copy. Cheapest wide angle I have tested for IR and the only one that worked. FA28mm AL @ F/8 and 120 seconds. Biggest Tombstone in Finland. Neewer 850nm IR Filter and channel swap in Photoshop. Yeap, you really need converted camera to get not blurry folliage. Today I get my second K-1 body (used 22000 shutter count). I think I will convert my older one (73000 shutter count) to infrared camera. I would like to install 665 nm filter from Thorlab. It is just a question they could make custom dimensions filter. Still waiting for the answer. Their standard is 50.4x50.4 mm x2 mm thickness. Some examples from Pentax K-5, 640 nm filter (postprocessed)

06-07-2019, 08:07 AM	#26
MJKoski Veteran Member Join Date: Aug 2016 Posts: 1,784 Original Poster	I picked 720nm converted Fuji X-A3 from ebay. Safe option to start a "new hobby". Pentax glass fits with adapter.

07-06-2019, 07:33 PM	#28
pcrichmond Site Supporter Join Date: Sep 2014 Location: Bishop, CA Posts: 278	Nice to see the Zeiss handle so well. I picked up a MOG Diaplan projection lens from here on the forums to see how the longer triplet would work for UV. No hot spots in IR either for that one.

07-07-2019, 06:23 AM	#29
zapp Pentaxian Join Date: Jul 2011 Posts: 2,385	Zeiss sells their lenses also as an industrial line with extended spectral range. I would expect all of them to perform well, even with regular coatings.

10-01-2019, 06:13 PM	#30
travelswsage Site Supporter Join Date: Jun 2016 Posts: 385	I finally took the plunge and picked up a used sony a7rii and had Kolari convert to dual spectrum. Got a chance to test a bunch of lenses today and was pretty disappointed with most of the results. Used an 850nm external filter and Fotodiox adapters for the lenses. I didn't take notes as well as I should and I had to control the aperture with the novoflex adapters. Used 1 or 2 step up rings to get to 77mm filter size -- I'm not sure but I don't think this should impact quality except that I could not use a lens hood to help with flare. The good: Pentax 67 120mm. Best of all lenses tested (unfortunately, also the least useful lens). No hotspot at any aperture, not even at F32. Pentax 67 100mm. Good through F16. Hotspot appears at F22. The not so good: Zeiss ZK 25mm 2.8 Ok to 5.6, F8 useable. Zeiss ZK 35mm 2 similar to 25mm. Pentax DFA 28-105 Extremely flare prone, to the extent that it was difficult to tell what was flare and what was hotspot. Ok to 5.6 at most focal lengths. Not so good after. Lensbaby 56 Ok to F8. Increasing hotspot thereafter. Pentax DFA 100 macro; Ok to 5.6 or 8; increasing hotspot thereafter The ugly: DFA 70-210 2.8. Tested at 70mm, 100mm, 150mm. Generally only good wide open, some lightness at F4 and not really useable after that. This and the Sigma are real disappointments. Sigma 180 3.5 macro Ok to 5.6. Distinct hotspot thereafter. I have a couple of others yet to test but am waiting on some step up rings to arrive. If anyone has experience using any of these on a converted K-1 I'd be interested in hearing ...