Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
10-09-2010, 11:21 AM   #16
Veteran Member




Join Date: Aug 2010
Posts: 523
QuoteOriginally posted by Digitalis Quote
avoid ultrawide lenses with infrared, because not only hot spots you will also likely encounter some serious smearing due to the fact that IR wavelengths aren't as easily bent as visible light wavelengths are.
That's a pity, but understandably true...

So filter needs to fit on my 18-55 mm II kit lens and some fast A prime.

Are there hudge differences between IR filters and IR filters?
- Which type / brand should I get (best bang for the buck)?

I found a Dutch company that sell them (720 nm) NEW up 67 mm diameter from stock for less than 30 Euro's, including transport costs (they can also "make" bigger, but that takes time and at higher cost).

10-09-2010, 05:08 PM   #17
Veteran Member
creampuff's Avatar

Join Date: May 2007
Location: Singapore
Photos: Gallery
Posts: 3,955
QuoteOriginally posted by Digitalis Quote
avoid ultrawide lenses with infrared, because not only hot spots you will also likely encounter some serious smearing due to the fact that IR wavelengths aren't as easily bent as visible light wavelengths are.
Do you have specific examples of what this "smearing" is all about? Can you elaborate what the "smearing" should look like?
I myself have used an ultrawide like the DA 14mm with no issues and I know of other IR shooters using other brands with ultrawides who have not mentioned this issue.



IR modded *ist DL2 with DA 14mm f/2.8
10-09-2010, 05:14 PM   #18
Veteran Member
creampuff's Avatar

Join Date: May 2007
Location: Singapore
Photos: Gallery
Posts: 3,955
QuoteOriginally posted by JoepLX3 Quote
That's a pity, but understandably true...

So filter needs to fit on my 18-55 mm II kit lens and some fast A prime.

Are there hudge differences between IR filters and IR filters?
- Which type / brand should I get (best bang for the buck)?

I found a Dutch company that sell them (720 nm) NEW up 67 mm diameter from stock for less than 30 Euro's, including transport costs (they can also "make" bigger, but that takes time and at higher cost).
I have used external IR filters from Hoya, Cokin, B+W and generic made in China ones and even though they may all list a somewhat similar cutoff wavelength, they ALL show a different color/spectral rendition. Exposure times vary too.
10-09-2010, 05:34 PM   #19
Veteran Member




Join Date: Aug 2010
Posts: 523
QuoteOriginally posted by creampuff Quote
I have used external IR filters from Hoya, Cokin, B+W and generic made in China ones and even though they may all list a somewhat similar cutoff wavelength, they ALL show a different color/spectral rendition. Exposure times vary too.
The spectral bandwidth of those filters is typically pretty narrow and I don't see how one centered around 715 nm is better or worse than one centered around 730 nm. The effective width will determine the exposure time, but I (as you might expect) doubt impact on IQ...

10-09-2010, 05:42 PM   #20
Pentaxian
Digitalis's Avatar

Join Date: Mar 2009
Location: Adelaide.
Posts: 8,535
QuoteOriginally posted by creampuff Quote
Do you have specific examples of what this "smearing" is all about? Can you elaborate what the "smearing" should look like?
I myself have used an ultrawide like the DA 14mm with no issues and I know of other IR shooters using other brands with ultrawides who have not mentioned this issue. IR modded *ist DL2 with DA 14mm f/2.8
nice shot, I have seen this smearing with the sigma 12-24 f/4.5-5.6 EX DG on full frame cameras at the 12mm to 16mm range and it basically looks like really bad astigmatism. The DA 14mm f/2.8 you used for that image is quite acceptable. However, that may very well be due to the digital specific design of the DA series lens and the fact that it would be more inclined to project an image onto the sensor without the high incidence angle that legacy film lens designs tend to do.
10-09-2010, 05:52 PM   #21
Veteran Member




Join Date: Aug 2010
Posts: 523
Some where I also read reasonable stories on the Tamron 10 - 24 mm (but not at 10 mm...), probably better to put my "money" on a filter for the 18-55.

http://www.forumlogr.com/thread/yVWwwwSCEafn/Tamron-10-24-and-350D,-Infrared-revisited.html

Last edited by JoepLX3; 10-09-2010 at 06:15 PM.
01-13-2012, 08:46 AM   #22
Senior Member
siamthai's Avatar

Join Date: Mar 2010
Location: Svealand
Photos: Gallery | Albums
Posts: 172
I'd like to try to do some IR photography but I don't know which of my lenses would be best suited for this. Anyone who have any advice on what lens I'd choose? I have the following lensens to choose from

Pentax Asahi Auto-Takumar 85mm f/1.8
Pentax SMC DA 18-55 f 3.5-5.6 WR
Pentax SMC-DA 50-200 f/4,0-5,6 ED WR
Pentax Super-Takumar 50mm f/1,4
Pentax SMC-DA 40/2.8 Limited
SMC Pentax DA 12-24mmF4ED AL (IF)
Sigma 50-500mm 1:4-6.3 APO EX DG
01-13-2012, 08:55 AM   #23
Veteran Member
creampuff's Avatar

Join Date: May 2007
Location: Singapore
Photos: Gallery
Posts: 3,955
QuoteOriginally posted by siamthai Quote
I'd like to try to do some IR photography but I don't know which of my lenses would be best suited for this. Anyone who have any advice on what lens I'd choose? I have the following lensens to choose from

Pentax Asahi Auto-Takumar 85mm f/1.8
Pentax SMC DA 18-55 f 3.5-5.6 WR
Pentax SMC-DA 50-200 f/4,0-5,6 ED WR
Pentax Super-Takumar 50mm f/1,4
Pentax SMC-DA 40/2.8 Limited
SMC Pentax DA 12-24mmF4ED AL (IF)
Sigma 50-500mm 1:4-6.3 APO EX DG
see this list
https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/66895-ir-infra...tml#post671922

01-13-2012, 09:08 AM   #24
Loyal Site Supporter
eddie1960's Avatar

Join Date: Aug 2010
Location: Toronto
Photos: Gallery | Albums
Posts: 12,166
the Pentax 12-24 looks pretty reasonable as well. last FEbruary Tim (Blackcloudbrew) shot a single in with his ir modded K100d

blackcloudbrew's Album: Single in February - PentaxForums.com
01-13-2012, 10:16 AM   #25
Senior Member




Join Date: Jan 2010
Location: Stockholm
Photos: Albums
Posts: 125
I have just tested the IR photography and although I didn't give up on it completely it is not so high on my wishlist that I am ready to modify a DSLR to get a permanent IR camera. However I am trying to find some of the used Sony night-shot cameras (with switch to remove IR blocking filter) to by my entry point to IR photography.

Here are some of my observations with simple theoretical background:

1. Using IR filter with unmodified camera results in a very long exposure times, since the IR filter is used to block the visible light and the filter in front of the sensor is used to block IR light, resulting in very little light reaching the sensor.

2. Lenses are optimized for visible light so that the projection is sharpest in the visible part of spectrum. Since different wavelengths (read colours) have slightly different refraction index the colours (if not compensated) have slightly different focus points. The longer wavelengths bend less then the shorter in the same lens. In ordinary photografy the effect results in cromatic abberation (famous CA) whereas for IR the focus point should be slightly longer than for the visible light. CA can be addressed by the so called APO design where two or more lenses (or groups) are matched so that at least two wavelengths have same total refraction resulting in better resolution and smaller CA. This however does not have to be the case for IR since the wavelength differs more than those the lens was optimized for.

3. Softness and the border sharpness (or lack of it) should be more exagregated in IR compared to the visible light.

4. Hot spots tend to appear in cases when coating and the glas material reflect IR light from some surface thus leading to multiple reflections (similar to ghosting when taking photo of a bright light source).

5. Lenses with harder glass (LD - low dispersion lenses) have bigger refractive index so that the relative dispersion between different wavelengths should be smaller than with lenses with some plastic elements, which should result in sharper images.

6. It should be interresting to see some IR photos made with mirror lenses, since mirrors are purely reflective surfaces and should exhibit any CA, thus bending (or reflecting) all wavelengths at the same path. Actually more info about reflective vs. refractive lenses in generals can be found on many astronomy forums.

Well, I hope I didn't get too theoretical with my post. Cheers!
01-13-2012, 11:54 AM   #26
Veteran Member
Nachodog's Avatar

Join Date: Dec 2007
Location: Montreal, Qc
Posts: 457
FWIW I found that the Sigma 10-20 is decent with IR.
01-13-2012, 01:16 PM   #27
Senior Member
siamthai's Avatar

Join Date: Mar 2010
Location: Svealand
Photos: Gallery | Albums
Posts: 172
I think every input is welcome so keep writing about how you all find how good or bad different lenses are for IR photos (^_^)
01-14-2012, 03:13 AM   #28
Pentaxian
Digitalis's Avatar

Join Date: Mar 2009
Location: Adelaide.
Posts: 8,535
The FA31mm f/1.8 and FA77mm f/1.8 Limited lenses are excellent for IR, the Pentax SMCP-K 50mm f/1.2 is also superb - because of the lens ultrawide f/1.2 aperture it is actually possible to focus the image in the viewfinder, though it does take your eyes a while to adjust to the darkness.

QuoteOriginally posted by stanislav Quote
5. Lenses with harder glass (LD - low dispersion lenses) have bigger refractive index so that the relative dispersion between different wavelengths should be smaller than with lenses with some plastic elements, which should result in sharper images.
I don't think so, the DA15mm f/4 Limited ASPH uses a hybird aspheric which is a glass lens bonded to a plastic aspherical lens - and the corner sharpness from the DA15mm f/4 limited isn't anything to write home about in the IR spectrum.

DA15mm f/4 flare with hoya R72 filter lens aperture @ f/4 - but the flare is still bad even at f/16.

Last edited by Digitalis; 01-14-2012 at 03:21 AM.
01-14-2012, 09:09 AM   #29
Pentaxian
RonHendriks1966's Avatar

Join Date: Jan 2009
Photos: Gallery
Posts: 8,556
I have a 49mm 720nm filter, but only used it a few times.

On DA21mm there is a hotspot.
01-14-2012, 05:38 PM   #30
Veteran Member
creampuff's Avatar

Join Date: May 2007
Location: Singapore
Photos: Gallery
Posts: 3,955
One thing I've noticed is there is definitely a difference if the lens tests were done with a standard camera with an an IR filter mounted in front of the lens or if the lenses were used on an IR-modded camera.

When used on an IR-modded camera, some lenses don't show obvious hotspotting when compared to lenses with an IR filter mounted in front. I can only surmise that either the shorter exposure times or the possible internal reflections from a front mounted IR filter are responsible for exacerbating the hotspots and internal reflections. One thing I do know is that results from an IR-modded camera that I'm using are a lot sharper and show better detail compared to when I used a normal IR filter on a conventional un-modded camera.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
k-mount, lenses, pentax lens, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
IR (Infrared)friendly pentax lenses? digitaldaydreams Pentax SLR Lens Discussion 11 10-03-2016 02:15 AM
A first try at infrared photography (2 pics) tcom Post Your Photos! 4 10-09-2010 06:17 PM
K-X and infrared photography Augustus58 Troubleshooting and Beginner Help 17 03-19-2010 06:45 PM
Usable lenses on a Kx or? aliasant Pentax SLR Lens Discussion 1 02-12-2010 09:29 AM
Infrared Photography with a non-converted K10D Slowpoke Rodriguez Pentax DSLR Discussion 14 08-09-2008 07:57 PM



All times are GMT -7. The time now is 04:01 PM. | See also: NikonForums.com, part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top