IR problem

Ghost in the Shell · 5 Apr 2006 at 20:50

hi just starting to try IR and i know this shot has more wrong than right but the main problem i want to clear up is the flaring (if thats what it is)

can anyone help explain what i am doing that produces this problem and how to stop it etc?

KIT:

10D with 50mm f1.4 USM & Hoya R72 IR Filter

Sleepyd · 5 Apr 2006 at 20:59

Hood?

AdWright · 5 Apr 2006 at 21:01

You've got a hot spot - internal reflections within the lens caused by the coatings on the glass. The 50mm 1.4 is known to do this, the 1.8 doesn't suffer from it apparently

Ghost in the Shell · 5 Apr 2006 at 22:51

great thanks for clearing that up adwright, is there anything i can do or is this something that cant be helped with this combination. any info i can read up that you know about?

ST8 · 5 Apr 2006 at 23:17

Select the blue channel in photoshop (or red if youve swapped channels) and then use the burn tool with a radius slightly bigger than the hotspot. That looks pretty intense so your milage may vary

Johnny|lucidcomposure · 5 Apr 2006 at 23:57

The problem you are experiencing is your shooting into the path of the sun. with such long shutter timings you are getting the suns flare. Try again but have the sun a clear 180Degrees behind your shooting path and you should achieve more pleasing results.

Ghost in the Shell · 6 Apr 2006 at 00:24

Fstop11 said:
The problem you are experiencing is your shooting into the path of the sun. with such long shutter timings you are getting the suns flare. Try again but have the sun a clear 180Degrees behind your shooting path and you should achieve more pleasing results.

sorry fstop but i think your wrong, this isnt the case i was careful not to be pointing to the sun - the other posters are spot on (scuse the pun) its a hot spot due to the lens construction

Ghost in the Shell · 6 Apr 2006 at 00:26

ST8 said:
Select the blue channel in photoshop (or red if youve swapped channels) and then use the burn tool with a radius slightly bigger than the hotspot. That looks pretty intense so your milage may vary

ok thanks for the tip, i was shooting at totally the wrong settings so i am hoping once i learn how best to take the shot the results will be more workable. again though is there any stuff to read about hotspots for myself?

thanks

Johnny|lucidcomposure · 6 Apr 2006 at 00:43

Sorry my bad. I read it as you had the F1.8. Very sorry for my poor reading.

Ghost in the Shell · 6 Apr 2006 at 01:21

Fstop11 said:
Sorry my bad. I read it as you had the F1.8. Very sorry for my poor reading.

no worries just stoppin it from slipping off the real issue

AdWright · 6 Apr 2006 at 09:51

Ghost in the Shell said:
great thanks for clearing that up adwright, is there anything i can do or is this something that cant be helped with this combination. any info i can read up that you know about?

Unfortunately, I think that the superior 50mm 1.4 is not going to be able to match the 1.8 in producing IR images. If I were you, I'd go out and pick up a 1.8 for your IR work - they're fairly cheap at only £65 or so.

For alternatives check out this thread over at POTN.
http://photography-on-the.net/forum/showthread.php?t=18698