[digitaldaydreams]

First of all Hello to all. I'm new here.

Is there a list of IR (Infrared)friendly pentax lenses online, all I can find is canon stuff?

This is for an IR modified K10D with 680nm pass filter internally installed. I just ordered the camera.

I have these pentax lenses (and a tamron) and I was wondering which of ones of these is the least prone to hot spots.

I usually shoot wide so I was hoping that at least one of my wide lenses is ok for this

Pentax DA 12-24mm

DA Limited 21mm

FA Limited 43mm

Pentax DA 16-45

Pentax DA* 50-135

Tamron 90 (prime)

Pentax DA 55-300

Pentax DA*300mm

Thanks for any help
frank

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Last edited by digitaldaydreams; 07-17-2009 at 07:40 AM.

[Duck Dodgers]

First, welcome to the forums!

Second, and maybe I'm missing something here, but why wouldn't any lens be IR-friendly? Even the old ones had IR focus-compensation lines.

[digitaldaydreams]

not sure why but,

it's my understanding after looking at various IR sites that
some lenses produce a hot spot (bright spot) in the picture, ruining the photo.
some lenses don't do that.

I was hoping that some IR shooten pentaxians would know the where abouts of a lens list for IR friendly pentax lenses and see if any of my lenses listed at the beginning of my post are going to work out for me.

I have a pretty good lens assortment and bought an IR modded pentax k10d becuase I already have pentax lenses and figured that 1 or 2 would work well with IR

[ivoire]

I can't answer the question but I'd like to know where you got the modified K10 and if more are available

[creampuff]

The term IR-friendly relates to the issue of hot-spotting, whereby digital IR images shot with certain camera lenses exhibit noticeable bright or uneven exposure, typically in the center of the IR image.
The degree of hot-spotting does vary with the aperture in use, so even if a lens does show mild hot spots, it can sometimes be managed by using a wider aperture when shooting.
The IR focusing mark found on many legacy lenses is to compensate for the shorter wavelength compared to the visible spectrum when shooting infrared sensitive film, which is quite different compared to digital IR photography. Cameras that have been converted to IR-only use also need to have their AF tweaked in order to compensate for the shift in wavelength. Stopping down a lens to increase DOF can mask slight focus errors if the camera's AF has not been tweaked.

There was an earlier thread listing out whether some lenses exhibited hot-spotting here:
https://www.pentaxforums.com/forums/general-photography-techniques-styles/364...ed-bodies.html

Pass - No hot spots

DA 14mm
DA 15mm Limited
DA 17-70mm SDM
DA 18-55mm
DA 18-55mm II
DA 18-55mm WR
DA 18-250mm / Tamron 18-250mm
DA 21mm
FA 20-35mm
FA 28mm
FA 28-70mm f/4
FA 28-200mm
A 35mm f/2, DA 35mm f/2.8 Macro Limited
FA 50mm f/1.4, FA 50mm f/1.7, A 50mm f/1.4, A 50mmf/1.7, A 50mm f/2
DA 70mm
FA 77mm Limited
FA 135mm
DA* 300mm / FA 300mm
DA 50-200mm, DA 50-200mm WR
DA 55-300mm, DAL 55-300mm
Sigma 28mm f/2.8 (manual focus)
Sigma 50mm f/2.8 (manual focus)
Sigma 17-70mm f/2.8~4.5
Lensbaby II

Fail - Clear or varying degree of hot spots

DA 12-24mm (slight, when stopped down in bright conditions)
DA 16-45mm (clear irregular hotspot)
DA* 50-135mm (slight)
FA 50mm Macro (slight, noticeable when stopped down)
DFA 50mm Macro (very slight up to f/4, worsens when stopped, better than FA 50mm macro)
DA* 55mm (visible)
FA 100mm Macro f/2.8 (very slight)
Sigma 10-20mm (visible, depends on scene)

The trend is many modern zooms and macro lenses don't fare particularly well.

[digitaldaydreams]

search ebay for converted pentax he is the only one showing an ir pentax ( k100 i think)

you can email him about a k10

[digitaldaydreams]

Thanks creampuff, nailed it, exactly what i was looking for.

[blackcloudbrew]

Please add the DA*55 to the hot spot list.

[Vitalii]

Pentax smc-A 28mm f2.8 - Hotspot with Filter.
Any 3d party lenses lists?

[Not a Number]

Note: precisioncamera in CT will do IR conversions. It appears precisioncamera will be the main service center for Ricoh/Pentax.

Lens Hotspot Performance Database | Kolari Vision Infrared

[clayhaus]

Spencer's Cameras in Alpine Utah will also IR-convert just about any camera.

[lacy]

The term IR-friendly relates to the issue of hot-spotting, whereby digital IR images shot with certain camera lenses exhibit noticeable bright or uneven exposure, typically in the center of the IR image.
The degree of hot-spotting does vary with the aperture in use, so even if a lens does show mild hot spots, it can sometimes be managed by using a wider aperture when shooting.
The IR focusing mark found on many legacy lenses is to compensate for the shorter wavelength compared to the visible spectrum when shooting infrared sensitive film, which is quite different compared to digital IR photography. Cameras that have been converted to IR-only use also need to have their AF tweaked in order to compensate for the shift in wavelength. Stopping down a lens to increase DOF can mask slight focus errors if the camera's AF has not been tweaked.

There was an earlier thread listing out whether some lenses exhibited hot-spotting here:
lenses for IR converted bodies - PentaxForums.com

Pass - No hot spots

DA 14mm
DA 15mm Limited
DA 17-70mm SDM
DA 18-55mm
DA 18-55mm II
DA 18-55mm WR
DA 18-250mm / Tamron 18-250mm
DA 21mm
FA 20-35mm
FA 28mm
FA 28-70mm f/4
FA 28-200mm
A 35mm f/2, DA 35mm f/2.8 Macro Limited
FA 50mm f/1.4, FA 50mm f/1.7, A 50mm f/1.4, A 50mmf/1.7, A 50mm f/2
DA 70mm
FA 77mm Limited
FA 135mm
DA* 300mm / FA 300mm
DA 50-200mm, DA 50-200mm WR
DA 55-300mm, DAL 55-300mm
Sigma 28mm f/2.8 (manual focus)
Sigma 50mm f/2.8 (manual focus)
Sigma 17-70mm f/2.8~4.5
Lensbaby II

Fail - Clear or varying degree of hot spots

DA 12-24mm (slight, when stopped down in bright conditions)
DA 16-45mm (clear irregular hotspot)
DA* 50-135mm (slight)
FA 50mm Macro (slight, noticeable when stopped down)
DFA 50mm Macro (very slight up to f/4, worsens when stopped, better than FA 50mm macro)
DA* 55mm (visible)
FA 100mm Macro f/2.8 (very slight)
Sigma 10-20mm (visible, depends on scene)

The trend is many modern zooms and macro lenses don't fare particularly well.

Is anybody have experince with da*16-50 f2.8? I can't find it on any list.