Author Topic: Questions and Answers on IR  (Read 91470 times)

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Offline pcabot

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Re: Infrared Photography using A700 and R72 : cannot get false color result
« Reply #75 on: September 09, 2009, 01:24:30 PM »
Wow !
Nice picture groovyone !
This is exactly what I am trying to achieve !

Hmmm. I think you are right: I will try to remove my UV filter from my lens, before adding the IR filter.
The only problem is that my UV filter seems "stuck"....

Do you have any trick on how to remove a filter that is attached very tightly (on  my SAL16105) ?

Thanks,
Phil

Offline Rob aka [minolta mad]

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Re: Infrared Photography using A700 and R72 : cannot get false color result
« Reply #76 on: September 09, 2009, 09:30:00 PM »
There are some filter tools specifically for removing stuck filters, i got some off ebay. But have used a leather belt when out in the field before.

As for the picture being exposed properly, i use the historgram (red channel) but also take a close look at the image on the LCD at 100% to see if its blown out or underexposed.


Rob

Offline pcabot

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Re: Questions and Answers on IR
« Reply #77 on: September 10, 2009, 02:02:16 PM »
Allright !
I successfully removed my UV filter and I tried again to take an IR picture with my R72.
I think that the UV filter was the source of my problem! Good to know !

What a difference now:



But now I have another question:
How is it possible to obtain a photo with white trees AND a blue sky ?
Do we need to do some manual selection in photoshop and process the sky differently ?

Thanks for the feedback,
Philippe

Offline winjeel

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Re: Questions and Answers on IR
« Reply #78 on: September 10, 2009, 02:48:46 PM »
That looks great. Good to know that your UV filter really is a UV filter and that it does its job well. :D
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Offline Rob aka [minolta mad]

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Re: Questions and Answers on IR
« Reply #79 on: September 10, 2009, 05:24:20 PM »
Any chance you could PM me or put up a link to the RAW file, as i just tried to channel swap the colours on the image of yours above, and not alot happened ???
Even with your last image it was difficult to get a great deal of colour from the image, particularly the sky which is unusual, and i cant work out what is going on ???

Here is an image straight from camera


and here is one that has been colour swapped


Not the best image to show off the blue sky that you are after, but i think its what you are trying to achieve ???

A couple of questions.
What did the sky look like when you took the shot, hazy, murky, very clear and dark blue, light blue ???

We will get there in the end.


Rob

Offline groovyone

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Re: Questions and Answers on IR
« Reply #80 on: September 10, 2009, 07:07:12 PM »
Allright !
I successfully removed my UV filter and I tried again to take an IR picture with my R72.
I think that the UV filter was the source of my problem! Good to know !

What a difference now:



But now I have another question:
How is it possible to obtain a photo with white trees AND a blue sky ?
Do we need to do some manual selection in photoshop and process the sky differently ?

Thanks for the feedback,
Philippe

You may want to boost your exposure a little bit more to get the trees more white.  As for the color change, I get the photo where I want in with the white trees, then I use Photoshop Elements 5 to shift the hue until I get it where I want.  Not as good as the color channel swap, but it works if you only have PSE.

In Camera (custom WB):


Hue edits and B&W:


Offline groovyone

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Re: Infrared Photography using A700 and R72 : cannot get false color result
« Reply #81 on: September 10, 2009, 07:10:32 PM »
Wow !
Nice picture groovyone !
This is exactly what I am trying to achieve !

Thanks,
Phil

Thanks!

Offline pcabot

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Re: Questions and Answers on IR
« Reply #82 on: September 11, 2009, 12:26:18 PM »
Thanks a lot winjeel, Rob and groovyone !
The blue pictures are *exactly* what I am trying to achieve!

When I took this picture, the sky was light blue (early morning).

Here is the ARW file, if anyone wants to try to turn it into a blue picture, with white trees, that would be great. (this is the raw file of the picture without the UV filter, just with the R72, so in theory it should work):

http://philippecabot.com/infrared2.arw  (15Mb)

I suspect again that my exposure was not right,, may be not, because I was not able to obtain the simultaneous blue/white effect, even when playing with the Hues.

Also, correct me if I am wrong, but I don't need to set the white balance in my camera before taking the picture ? Right ? The entire goal of shooting RAW is to be able to adjust the WB after the fact. I read somewhere on the web that if you adjust your white balance before taking the shot, the information captured in the RAW might be different ? Is that true ? I don't think so...

Thanks again for all your time and feedback.
I really like to learn from the pros, and also to share my experiments !
Philippe


Offline groovyone

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Re: Infrared Photography using A700 and R72 : cannot get false color result
« Reply #83 on: September 11, 2009, 04:42:09 PM »
Great shots- grovyone! Just a quick one- you do have a converted IR camera? Any reason why you shot this with a filter on the A700??? I have just sent my A100 off for IR conversion as I don't need this camera body for anything else. Which gives the better results: the converted camera or the A700 with filter???
Stef.

Sorry, I had missed this post.  I shot this before I had my IR converted A100.  I think they give slightly different results.  The converted is much easier to use but you seem to get a little less "drama".  The A700 got more reds which would be deeper than I have gotten with some of my converted camera shots.

pcabot -
On the blues, I like them for pure nature/landscape shots, but they are TERRIBLE for people.  It tends to make skintones a sickly green.  Sometimes buildings will look better with the warmer tones too.
« Last Edit: September 11, 2009, 04:47:09 PM by groovyone »

Offline Rob aka [minolta mad]

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Re: Questions and Answers on IR
« Reply #84 on: September 11, 2009, 04:59:01 PM »
Also, correct me if I am wrong, but I don't need to set the white balance in my camera before taking the picture ? Right ? The entire goal of shooting RAW is to be able to adjust the WB after the fact. I read somewhere on the web that if you adjust your white balance before taking the shot, the information captured in the RAW might be different ? Is that true ? I don't think so...

I have heard and read debates about this before, there is a possibility that the information captures would be better if the white balance was set in camera (never came to a conclusive decision on all the stuff i read) perhaps Stef could give us a more technical answer ???

The one thing i did find with having an in camera white balance was that it was easier to check for correct exposure.

Have downloaded your image, and will have a look at it later.


Rob

Offline Stef.

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Re: Questions and Answers on IR
« Reply #85 on: September 11, 2009, 10:44:22 PM »
Also, correct me if I am wrong, but I don't need to set the white balance in my camera before taking the picture ? Right ? The entire goal of shooting RAW is to be able to adjust the WB after the fact. I read somewhere on the web that if you adjust your white balance before taking the shot, the information captured in the RAW might be different ? Is that true ? I don't think so...

I have heard and read debates about this before, there is a possibility that the information captures would be better if the white balance was set in camera (never came to a conclusive decision on all the stuff i read) perhaps Stef could give us a more technical answer ???

The one thing i did find with having an in camera white balance was that it was easier to check for correct exposure.

Have downloaded your image, and will have a look at it later.


Rob

Yes. It is better to get the white balance in camera correctly as if you correct it later on you will have a difference in exposure. It is jsut a slight difference but sometimes critical. In a nutshell: the more you get in camera correctly the better it is as you need to do less post-processing. I am not speaking about a time saver here but more about image quality.
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Offline Rob aka [minolta mad]

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Re: Questions and Answers on IR
« Reply #86 on: September 12, 2009, 09:09:36 PM »
Have had a play with your image, and when trying to colour swap the whole image goes blue, and doesnt come out at all like i would expect.
With your Raw file, its not as deep red as i would expect either, and i sort of think that the levels of IR light around arent at their best, and that the  sky isnt absorbing the IR light allowning for it to be turned blue with the trees white like you are trying to achieve.
I have experienced weird effects before where images just would not come out at all, while shooting early morning at the seaside.
All the shots i took just produced a pink foggy haze, and no matter what i tried i couldnt cure it. This was also early in the morning, and once the sun came up the images were fine.

One thing i will say though is that your exposures need to be longer, as to get what id regard as the right exposure i had to increase it by nearly 2 full stops, probably another 8-10 seconds in real terms (though this is always dependednt on what IR light is present)

Try taking an image around midday with the sun behind you, varying exposures and then let us know how you get on.
Could be worth trying them with an in camera white balance as well.


Rob

Offline pcabot

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Re: Questions and Answers on IR
« Reply #87 on: September 12, 2009, 11:43:06 PM »
Hi Rob,

Thanks for trying to convert the image.

I took other pictures this afternoon.
I tried to set up  the white balance in my a700 with the R72 filter on, and the WB value becomes 6600K G9 ? Is this normal ? In all case, I was still able to process the image in photoshop normally.


I also tried to use longer exposure (around 1 minute), and still no differences: I cannot get any colors in post processing :

Here is the histogram of the RAW file before processing :


Is it the expected histogram ?
What should the histogram look like for a photo that can be converted successfully in color (blue/white) ?

I still need to try at noon, to see if the IR is stronger. But, I start to wonder if my Hoya R72 filter is a "real" one....

Did anyone else experienced the same problem ?
By the way, is there any setting on the A700 that could cause the problem ? I have dynamic range set to normal, but again, if I shoot RAW, it should have no effect according to me...

Thanks again for the feedback,
Philippe

Offline Rob aka [minolta mad]

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Re: Questions and Answers on IR
« Reply #88 on: September 13, 2009, 07:08:18 PM »
As long as the DRO is turned off, then any other settings wouldnt make too much difference.
As for the historgram, id say it was under exposed, as it is clipping the shadow (right) and a more even one from left to right would be better.
This is the historgram taken of the RAW file for the image above


As for the Custom WB i always seem to remember mine being around 2200k - 2450k G9 ???

Interesting that you mention about the Hoya filter as it was one thing that i ruled out, knowing that it was a Hoya R72 (is it a genuine Hoya filter ???) there are some copy's of the hoya filters, but id not heard of the IR ones being copied.

Could be worth checking carefully to see if it a genuine one.


Rob

Offline groovyone

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Re: Questions and Answers on IR
« Reply #89 on: September 14, 2009, 03:03:47 AM »
Mine is 2800K G9 on my modded A100, which works great with my 24-70Z, but I have a blue color shift with my 24/2.8. 28/8 and 50/1.4, so I need to work on a new one for those lenses.