Photoclubalpha

Complete newbie IR questions

On the recent "Trees" picture thread (http://www.photoclubalpha.com/forum/vie ... =17&t=3711) John showed a beautiful IR image taken using a filter. I wanted to ask for some suggestions around IR filters, but I thought it better to do it away from the Tree thread so it didn't get hijacked with a gear discussion. John warned me of using anything too flimsy (I think). I was considering this product from Cokin:
http://www.warehouseexpress.com/buy-cok ... r/p1000762
UK Ebay stores seem to have this for about £20. Is this the same product that you have John? Anybody else have any suggestions? I wanted to find a filter option rather than going for the expense of converting a body (which I understand is another option?).

I have found this site http://www.dpfwiw.com/ir.htm which talks about IR photography, anybody body else have any suggestions?

I'll ask Armen. He was on his way to try some IR shots. I'll give him a call tomorrow.
BTW, AFAIK you cannot make IR shots with either Nikon or Canon. You have to remove the inner filter. Correct me if I'm wrong.

Thanks Doc.

Birma- that filter that you linked to is the one I bought after I got something on the cheap gel filter that came with the SFX film. It works just as well, but I haven't tested it much since winter is here. It too seems to scratch easily, but I may have not been careful enough when I used a lens cloth to wipe it off.... The price you can get from ebay is about what I paid for mine. I looked at this website before I did my first shots with IR.http://www.teddy-o-ted.com/tutorials/a- ... otography/
Doc- I think you are correct that canikon can't do IR without a conversion. A conversion (even on a Sony body) would likely get you shorter shutter speeds. Plus you could actully compose the photo thru the viewfinder without having to remove an almost opaque filter.
I am eager for spring to do more IR. I am already scouting locations. Looking foward to some IR threads!! John

Useful information John I will look in to getting one of the Cokin filters and eagerly await spring also (just some sunshine would be nice as well). Nice to learn of a possible Sony advantage .

Hi everybody!!
Sorry for my absence for a while, again I am engaged in many jobs and studies and I have lack of time
Dear Birma I have just started to experience with IR photography because I liked a lot after having a look to some images of my friend who
has been experiencing in it for a long while. At first I read somewhere that my Minolta 35-70 f4 is infrared compatible lens and I have also read in the internet that a700 is sensitive to some part of IR radiation and some nice images can be shoot without any camera modification.
But I also knew that I will need a high shooter speed values like 20 or more seconds for sunny winter day. Hence I took 3 filters form ebay.
One was 720nm Hoya filter which is very famous and qualitative filter. Another 2 were 850nm and 950nm filters which are mainly capturing in black and white tones. As it was supposed I liked the 720nm filter more because of some colors.. But I still have a problem I can't get sharp images as I was planning. I start thinking that my Minolta lens's antireflective coatings are not antireflective any more in the infrared region of electromagnetic wave spectrum which is the reason of some glare in my images. In IR photography it is common to set the white balance according to the blue clear skyes, but whenever I try to do it my camera shows WB error which means that it is not supposed to have that kind of WB values I don't know why. If you can explain I will be happy. Hence I capture in autoWB mode after which I change it in lightroom, but I don't like this way. Of course I didn't try to capture many images I did only a few and even the sun radiation level was bad which is I think quite important. Simply I didn't have time, I am going to tray in a nearest opportunity. By the way my friend has modified a few point and shoot cameras removing the inner hot mirrors which block the IR radiation and the sensitivity of theur CCD's are quite good, he is able to capture without a tripod and he is observing the real image appearance in the life view mode which is not present on my A700. I am sure that the best way is to start form point and shoot with corresponding filters. But what about the filters I think that Hoya 720 is also a good solution.

With an IR filter on, the lenses will focus wrong. I think a little front focus, I remember my film lenses all had an adjustment dot or another scale to focus IR with because what you saw through the VF isn't what you get when the filter is on. could that be why your pictures are fuzzy?

The 'red dot' is very helpful in IR photography (too bad most modern lenses don't have it). I use my 28-85 just for that reason. Often companies that convert to dedicated IR will also re calibrate focus. 720nm on up refracts differently through the lens glass than visible light does.
Javelin I think you are right that it will front focus.
I usually have my a200 set to RAW with auto WB and creative style turned to B/W. But at this point I am more interested in B/W IR images.
I also try to keep the sun at my back.
Somewhere I found a link to a chart that showed IR reflective indexes. It was good for choosing subject matter. If I can find it again I will post it. Hope this helps. John
P.S. I have been told that midday will have the most IR reaching the Earth's surface.. I guess due to travelling through less atmosphere.

Thanks Armen and John. Some very useful information there. The front focus issue looks a challenge, I guess wide angle lens with small aperture will increase DOF and help?

Of course I agree with you in observing the difference between IR and visible light and a few problems which can occur, but in case of I capture landscape under 35mm with f9 I don't think there should be so much difference in focusing, am I right or not? Probbly wider lens will be appropriate for this aim but my filters are all for 49mm diameter and I haven't know any choice to try my 16-105 with IR which diameter is bigger

Armen Gharib wrote:Of course I agree with you in observing the difference between IR and visible light and a few problems which can occur, but in case of I capture landscape under 35mm with f9 I don't think there should be so much difference in focusing, am I right or not? Probbly wider lens will be appropriate for this aim but my filters are all for 49mm diameter and I haven't know any choice to try my 16-105 with IR which diameter is bigger

Armen, I can lend you my 28/2.8 if you want. It has 49mm filter diameter.

I just checked that the 35-70/3.5-4.5 has also the same filter diameter. So I can lend that too.

Armen- You are probably correct on the focus at f9. Interestingly enough, there are 5 IR numbers on the the lens 88 (70 assumed), 50, 35(assumed), and 28. I guess that focus will change at different focal lengths. Does anybody out there know the scientific answer?

The infrared index moves as you zoom (some lenses used to have a multiple or graph-like IR marker). As a guide, focusing approximately 6/7ths of the actual distance will correct a narrow-cut infrared filter - for 35ft, focus at 30ft - for infinity, focus around 50ft.

There is no accurate indicator for infrared at close distances, even the marker on lenses ceases to be accurate (it is positioned to show the adjustment needed at infinity). However, you may find that with an R72 filter in position, your AF will still work even if you can't see anything. That's because the AF sensor retains some IR sensitivity, but has no IR filter over it (some do).

If you can get AF/MF confirmation to operate, you are also likely to getting correct IR focus.

David

Thanks for the clarity David. To be honest I have always set the camera to MF for IR. I'm going to try it on AF in spring and see how it does. John