Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
07-28-2012, 12:40 PM   #1
Forum Member
bricamry's Avatar

Join Date: Jul 2012
Location: Prague, Czech republic
Photos: Albums
Posts: 82
lenses suitable for IR

Hello i bought IR 720nm filter and used on A 28/2,8...
there is one of first tries:

problem is the hot spot in the center, i am unhapy from it... IMHO kit 18-55 is not giving that spot, right?
my next question is, if you know, that A 50/1,7 isd giving this fault or not? very thanks! )

07-28-2012, 01:31 PM   #2
Veteran Member
Jools's Avatar

Join Date: Aug 2009
Location: SW Wisconsin by way of Venezuela
Photos: Gallery | Albums
Posts: 1,383
I don't really see the hotspot. Perhaps it is my monitor but I don't see it. Now, if you see it then it must be an issue. I have had the same issue arise under certain light conditions (and it can be quite irritating). It does not happen all the time just under certain harsh light and depending on the f-stop. (I usually go with f11-16)

I take IR images with a converted K-x and use a number of lenses. For instance, the kit lens works well as do the Sigma 10-20mm, Auto Sears 55mm f1.4, Porst Weitwinkel Auto F 28mm f2.8, Tamron 75-250mm f3.8/4.5 Adaptall-2 (104A), and the SMC Macro Takumar 50mm. These are my favoritie lenses with IR.

My converted IR body is full spectrum (clear glass) so I use various filters in front of the lenses.

What camera body are you using? It could also be the filter. I have an Opteka IR 720nm that produces hotspots unlike other filters. Just a thought.
07-28-2012, 03:07 PM   #3
Forum Member
bricamry's Avatar

Join Date: Jul 2012
Location: Prague, Czech republic
Photos: Albums
Posts: 82
Original Poster
it is not strong, but it is there!
here see:K-r + A28/2,8 & F8 (my first ir image... )


there is hotspot more visible...
it si irritating... okay... i maybe will use kit lens... but without DOF scale it willl be harder.... :/

my filter: Green-L 58mm IR 720nM ... costs about $23 ...

i hope, that with A50/1,7 (i gonna to buy) it will be ok...

by the way: how process in Adobe Camera RAW are you using?
i used wb on 2000K , lowered saturation of oranges and hue for oranges to yellow, yellow to green...
07-28-2012, 03:52 PM   #4
Pentaxian
Just1MoreDave's Avatar

Join Date: Feb 2007
Location: Aurora, CO
Photos: Gallery | Albums
Posts: 4,817
I used a Hoya 72 and the SMC Pentax-F 28mm f2.8 for this one. It was at f8, 0.5 sec, ISO 200 and an unmodified *ist DS. Processing was a quick 2000K temp., -72 tint, +0.35 stop exposure, 25 blacks, and a little luminance NR in ACR, then swapping the red and blue channels in the PS5 channel mixer.

The F28/2.8 is supposed to be the same design as the A version but I think Pentax changed the coatings somewhat on the F series. I haven't seen a hot spot with my lens but that doesn't mean much.



07-29-2012, 01:18 PM   #5
Forum Member
bricamry's Avatar

Join Date: Jul 2012
Location: Prague, Czech republic
Photos: Albums
Posts: 82
Original Poster
very thanks for your help, situation looks that, i'll mark hyperfocal distances on my kit lens and it will be it
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!
ir, k-mount, pentax lens, slr lens, spot
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Is IR filter suitable for K-r? Shingkyo Pentax K-r 16 06-01-2011 11:57 AM
suitable lens oldgoat Troubleshooting and Beginner Help 10 02-09-2011 04:06 AM
class 10 suitable for K-x? l3yl3y Pentax DSLR Discussion 18 12-19-2010 05:52 AM
Are those lenses suitable for Pentax? gnievko Troubleshooting and Beginner Help 3 04-20-2010 10:35 AM
what lenses are suitable for use with a reverse ring? Douglas_of_Sweden Pentax SLR Lens Discussion 17 06-25-2009 07:24 PM



All times are GMT -7. The time now is 04:50 AM. | 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