Full Frame Lenses Suitable for IR on the K-1?

**StevenLS** · 07-05-2017, 08:37 AM

What full frame lenses can be used for infrared photography on a K-1? Anyone have real world experience?

I can get a decent IR image on with the HD D FA 28-105mm lens, but it has serious vignetting which makes it practically useless unless some heavy cropping/post processing is done.

Medex · 07-05-2017, 09:06 AM

Last year i did try IR photography with K-1. I used Fa 31 mm Ltd and Revuenon 55 f1.2. The las one has hot spot and is not usable for IR.
Now I have modified Pentax K-30 and K-5. I have used Fa 31, Sigma 18-35 Art and Samyang 14mm and I am satisfied with results.
I you want to use K-1, you will need tripod and long exposure. Without tripod you have no chance to make sharp image. But with long exposure everything that moves a little will be in blured contours. This is the reason why you need modified IR camera that can make pictures with short exposure time.

**jatrax** · 07-05-2017, 10:46 AM

Originally posted by StevenLS

but it has serious vignetting which makes it practically useless unless some heavy cropping/post processing is done.

Never done any IR work but curious as to why this lens vignettes when shooting IR but not otherwise? Something with the light being different? Or is it just the filter that vignettes?

Medex · 07-05-2017, 11:05 AM

Originally posted by jatrax

Never done any IR work but curious as to why this lens vignettes when shooting IR but not otherwise? Something with the light being different? Or is it just the filter that vignettes?

Maybe that vignetting is some kind of hot spot? I observe ''vignetting'' with Sigma 18-35 Art when I use small apertures, e.g. f11-16. But in real world shooting with this lens I allways use f4 because it is the sharpest aperture.

**StevenLS** · 07-05-2017, 05:11 PM

Originally posted by Medex

Last year i did try IR photography with K-1. I used Fa 31 mm Ltd and Revuenon 55 f1.2. The las one has hot spot and is not usable for IR.
Now I have modified Pentax K-30 and K-5. I have used Fa 31, Sigma 18-35 Art and Samyang 14mm and I am satisfied with results.
I you want to use K-1, you will need tripod and long exposure. Without tripod you have no chance to make sharp image. But with long exposure everything that moves a little will be in blured contours. This is the reason why you need modified IR camera that can make pictures with short exposure time.

Medex, I was using f8, but I'll open up a stop and see if that solves the problem. I was shooting with a lens hood and I'll take it off. I've used the hood before with no problems. I do want to see what kind of IQ I can get with the K-1 without converting it.

Jatrax, I've seen some chatter somewhere about IR lens distorting images; but I don't recall the specifics. You are probably onto something.

Richard Gadd Richard Gadd - Google+ uses a K-7 with Samyang 8mm and DA 15mm and recommends them. Spencer Camera just converted my K-7 and I should receive it in several days.

07-05-2017, 08:37 AM	#1
StevenLS Site Supporter Join Date: Jul 2008 Location: Hartsville, SC Posts: 61	Full Frame Lenses Suitable for IR on the K-1? What full frame lenses can be used for infrared photography on a K-1? Anyone have real world experience? I can get a decent IR image on with the HD D FA 28-105mm lens, but it has serious vignetting which makes it practically useless unless some heavy cropping/post processing is done.

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07-05-2017, 09:06 AM	#2
Medex Pentaxian Join Date: May 2013 Location: Vilnius Posts: 1,020	Last year i did try IR photography with K-1. I used Fa 31 mm Ltd and Revuenon 55 f1.2. The las one has hot spot and is not usable for IR. Now I have modified Pentax K-30 and K-5. I have used Fa 31, Sigma 18-35 Art and Samyang 14mm and I am satisfied with results. I you want to use K-1, you will need tripod and long exposure. Without tripod you have no chance to make sharp image. But with long exposure everything that moves a little will be in blured contours. This is the reason why you need modified IR camera that can make pictures with short exposure time.

07-05-2017, 10:46 AM	#3
jatrax Site Supporter Join Date: May 2010 Location: Washington Cascades Photos: Gallery \| Albums Posts: 12,991	Originally posted by StevenLS but it has serious vignetting which makes it practically useless unless some heavy cropping/post processing is done. Never done any IR work but curious as to why this lens vignettes when shooting IR but not otherwise? Something with the light being different? Or is it just the filter that vignettes?

07-05-2017, 11:05 AM	#4
Medex Pentaxian Join Date: May 2013 Location: Vilnius Posts: 1,020	Originally posted by jatrax Never done any IR work but curious as to why this lens vignettes when shooting IR but not otherwise? Something with the light being different? Or is it just the filter that vignettes? Maybe that vignetting is some kind of hot spot? I observe ''vignetting'' with Sigma 18-35 Art when I use small apertures, e.g. f11-16. But in real world shooting with this lens I allways use f4 because it is the sharpest aperture.

07-05-2017, 05:11 PM	#5
StevenLS Site Supporter Join Date: Jul 2008 Location: Hartsville, SC Posts: 61 Original Poster	Originally posted by Medex Last year i did try IR photography with K-1. I used Fa 31 mm Ltd and Revuenon 55 f1.2. The las one has hot spot and is not usable for IR. Now I have modified Pentax K-30 and K-5. I have used Fa 31, Sigma 18-35 Art and Samyang 14mm and I am satisfied with results. I you want to use K-1, you will need tripod and long exposure. Without tripod you have no chance to make sharp image. But with long exposure everything that moves a little will be in blured contours. This is the reason why you need modified IR camera that can make pictures with short exposure time. Medex, I was using f8, but I'll open up a stop and see if that solves the problem. I was shooting with a lens hood and I'll take it off. I've used the hood before with no problems. I do want to see what kind of IQ I can get with the K-1 without converting it. Jatrax, I've seen some chatter somewhere about IR lens distorting images; but I don't recall the specifics. You are probably onto something. Richard Gadd Richard Gadd - Google+ uses a K-7 with Samyang 8mm and DA 15mm and recommends them. Spencer Camera just converted my K-7 and I should receive it in several days.