infrared filter comparison

[stradibarrius]

I am shooting my first roll in my F100 and am using an 89b opaque red filter. I have been guessing 4 stops. This first roll should at least get me in the ball park???

[keithwms]

Well, you should bracket, and I would suggest +0 through +5 for your first time. Your test bracket should have the optimal exposure somewhere in the middle. After that you are an ordained expert. (mind you, the IR light content can be vastly different depending on the weather and time of day, really altering your results by several stops)

[bsdunek]

I found I was ignorant on this too: http://www.apug.org/forums/forum37/6...velopment.html

Efke/Mako IR820 information does not recommend a filter higher than 720 nm. I had a Hoya R90 in my misc. stuff, which is 900 nm cut-off. On a sunny-16 day, my exposures were in the range of 16-32 sec. at f11. Additionally, the photos don't really look good. I've ordered a 720 nm filter for future use.

Amazing the education one can get when things don't work out!

[stradibarrius]

I am a violin maker and I can tell you I have learned more form my failures than my successes!
I know that where you shoot landscape the mid day lighting is not the best time, but it seems that is the time when you get the most IR????

[bsdunek]

I am a violin maker and I can tell you I have learned more form my failures than my successes!
I know that where you shoot landscape the mid day lighting is not the best time, but it seems that is the time when you get the most IR????

You have my respect! That is some of the best woodworking known.

[glbeas]

Yes, I've found mid day to be very productive for IR photography, the IR dark skies or the enhanced contrast of the clouds seem to be at it's peak then. I have shot late in the day successfully, and the ratio of IR to visible light tends to increase as the sun angle gets lower though the actual amount of IR is falling. That's well documented and is one of the reasons IR metering is so variable and hard to predict.

[keithwms]

My best times are indeed from around 11am-4pm. High noon is especially powerful with IR, the shadows fall very 'contrastingly.' Especially nice for stone and architecture and such.

[colrehogan]

Take copious notes! This will help you to improve rapidly.

[pentaxuser]

In RobertV's example 5 stops with the 88A filter reduces the ISO to 12 ( from 400 to 12) but if we apply the sunny f11 rule(as its N Europe) isn't it a little more than 6 stops? It would be 1/12th at f11 so 3 stops more to f4 gives nearly a 1/100th but Robert has used 1/30th in his example.

I am confused. The whole thing is made worse by the fact, as far as I recall, that when books and filter manufacturers mention filter factors I think I can recall that in my instructions with a pale yellow it mentioned a factor of 2 but went on to say this equates to 1 stop.

pentaxuser

[2F/2F]

Yes. It would be nice if each IR filter was simply supplied with a plainly stated cutoff wavelength. Some are obvious (The Heliopan RGs, for instance, or the Hoya R72), but other are not.

"I had a Hoya R90 in my misc. stuff, which is 900 nm cut-off. On a sunny-16 day, my exposures were in the range of 16-32 sec. at f11."

I am surprised you got anything at all. The film is not supposed to be sensitive to anything above 820 nM or so. Must be "leakage" of light below 900 nM.