IR: How to get the blue from the sky?

[jonchia]

Hi IRers,

First time with IR photograhpy. Saw some very nice pics in this forum. Did my shoots today. Can't seem to get the blue color from the sky. It show's up black. How come? Did all the pp suggested by Max 2.8

Goosberry, Vortex and Panda, if you are reading this, I am talking about the colors that you guys got from your shoots.

Thanks!

[TrailsofLife]

Play with your PS. Slide some bars in Hue & Saturation, Colour Balance etc. Should be able to get it unless your camera can only do monochrome.

By right, after Channel Mixer, your sky should be closed to blue already.

There's no standard formula, I've seen red sky as well. Just try any thing with PS.

[ark19]

Originally Posted by jonchia Hi IRers, First time with IR photograhpy. Saw some very nice pics in this forum. Did my shoots today. Can't seem to get the blue color from the sky. It show's up black. How come? Did all the pp suggested by Max 2.8 Goosberry, Vortex and Panda, if you are reading this, I am talking about the colors that you guys got from your shoots. Thanks!

Hi jonchia,
Perhaps you can post the original and ur PP pic here?
Easier to advise and give comments

[jonchia]

Hi ark19,

Wanted to post my pics but don't know how. Understand that there is one thread that talks about how to post pics. Could you help point me to that thread?

Thanks a mil!

[ark19]

Originally Posted by jonchia Hi ark19, Wanted to post my pics but don't know how. Understand that there is one thread that talks about how to post pics. Could you help point me to that thread? Thanks a mil!

Hi Jonchia,
pls refer to this thread

[gooseberry]

Only just saw this message now. Yeah, as the others have mentioned, to get the colours, you can play around with the Channel Mixer in PS and modify the values of the different channels.

Also, what camera are you using ? As is mentioned on another thread, some cameras aren't able to get coloured IR photos.

Post your images up and I'm sure we'll be able to help out.

[jonchia]

Hi ark19,

Thanks so much for the thread.

Here are the pics:



This one here did give me different colors. Played with a lot of things in pp.




This is the one which I could not get the blue color on the sky. Any suggestions?

[ark19]

Originally Posted by jonchia Hi ark19, Thanks so much for the thread. Here are the pics: This is the one which I could not get the blue color on the sky. Any suggestions?

No Prob jonchia
Is the 2nd pic the original file?
If you adjust the Hue settings, you will be able to see that the colours do shift. Just that most of the sky is blackish.
Which camera are you using?
Do you have a photo which shows "more" sky?

[gooseberry]

OK, looks like you're using a D70.

That second picture you've already played around with it ? Have you got the original that came out of the camera ?

[teerex]

jonchia,

Question: what did you use for reference to set you Custom White Balance?

From your picture, the sky has lots of black and the patch of cloud abover the roof of the building is bluish and the building walls also have a blue tint.

As that picture has already been processed, it would be quite difficult to do any adjustments to achieve the blue sky. Like gooseberry mentioned it would be helpful if you could post the out of the camera unprocessed picture for us to see.

I did some further pp with your processed picture. Still could not get a good blue sky. But I've eliminated the blue tinge from the clould and walls of the building. Some adjustments also on the leaves, but the blue in the sky is very false.

Post your unprocessed pic, may help in analysing.

[tomcat]

From my experience, if the sky is too clear, it would come out as black in digital IR. I have a couple of shots taken with the 10D that has totally black skies. This is likely to be due to the fact that the camera captures IR radiation that's reflected off objects be they buildings, plants or bellowy or thin wispy clouds. Those parts of the sky that's completely devoid of clouds would not reflect back IR radiation and would therefore appear black in digital IR.

[teerex]

Originally Posted by tomcat From my experience, if the sky is too clear, it would come out as black in digital IR. I have a couple of shots taken with the 10D that has totally black skies. This is likely to be due to the fact that the camera captures IR radiation that's reflected off objects be they buildings, plants or bellowy or thin wispy clouds. Those parts of the sky that's completely devoid of clouds would not reflect back IR radiation and would therefore appear black in digital IR.

Tomcat,
Would like to understand if the black skies results on a clear sky, maybe it's camera dependant due to the different sensors used?

Here're a couple of pictures shot (D70) with clear skies, but I'm able to get the blues. Just for point of discussion.

[TrailsofLife]

Try using centre-weight metering, so exposure is more even. Maybe you spot/partial metered the plants to prevent over-exposed or burnt spots on your images so the sky being darker will be slightly under-exposed?

Also depends on camera, Olympus 5050 on a clear day will still produce black sky because it can only do IR in monochrome!

[Pablo]

Hi teerex,

I realy like those 2 IR photo's

Kit lens all the way now

[teerex]

Originally Posted by Pablo Hi teerex, I realy like those 2 IR photo's Kit lens all the way now

Thanks Pablo. YES, Kit Lens all the way.

[tomcat]

Originally Posted by teerex Tomcat, Would like to understand if the black skies results on a clear sky, maybe it's camera dependant due to the different sensors used? Here're a couple of pictures shot (D70) with clear skies, but I'm able to get the blues. Just for point of discussion.

What I was referring to is an absolutely clear sky with no clouds whatsoever, no matter how thin they are. Such skies are not very common here in Singapore but they do occur once every so often and sometimes only for short durations and sometimes in small sections of the sky. Most of the time, when we get a 'clear' blue sky, there are actually very, very thin layer of clouds very high up which are not visible to our eyes but these reflect back enough IR to let the sky be post-processed to 'blue'.

So far this has been captured by Canon's CMOS sensors and Nikon's CCD sensors (jonchia's D70). So I don't think that it's really sensor dependent.

These are my examples:

[gooseberry]

Originally Posted by tomcat What I was referring to is an absolutely clear sky with no clouds whatsoever, no matter how thin they are. Such skies are not very common here in Singapore but they do occur once every so often and sometimes only for short durations and sometimes in small sections of the sky. Most of the time, when we get a 'clear' blue sky, there are actually very, very thin layer of clouds very high up which are not visible to our eyes but these reflect back enough IR to let the sky be post-processed to 'blue'. So far this has been captured by Canon's CMOS sensors and Nikon's CCD sensors (jonchia's D70). So I don't think that it's really sensor dependent.

Actually, it is very much dependent on sensor and the low pass filter that is on top of the sensor. In your first pic - the sky is almost totally covered in cloud and you've processed your picture so that the clouds have a blue tint to it - but the small patch of sky behind the cloud is quite dark.

Here is one of my pictures - which has a similar amount of cloud to that in jonchia's second picture (ie very little cloud to do any reflection)



Since he is using a D70 too - he should be able to get nice blues in the sky - notice that the clouds are white here and have no blue tint or very little.


What I've read is that the low-pass filter in Canon camera (10D, 300D etc) is much stronger and you therefore need very long exposure times.

[tomcat]

Originally Posted by gooseberry Actually, it is very much dependent on sensor and the low pass filter that is on top of the sensor. In your first pic - the sky is almost totally covered in cloud and you've processed your picture so that the clouds have a blue tint to it - but the small patch of sky behind the cloud is quite dark. Here is one of my pictures - which has a similar amount of cloud to that in jonchia's second picture (ie very little cloud to do any reflection) Since he is using a D70 too - he should be able to get nice blues in the sky - notice that the clouds are white here and have no blue tint or very little. What I've read is that the low-pass filter in Canon camera (10D, 300D etc) is much stronger and you therefore need very long exposure times.

The first pic was meant to illustrate my point that sometimes you do get openings in the sky with absolutely no clouds. And I did not process that pic to have clouds with blue tint. I was trying to get a blue sky. Sometimes, when the clouds are thin enough, a bit of the background show through and gives them a blue tint. I see the same effect in some of the clouds in your pics too. The pics I posted are those few pics that no matter how hard I tried to post-process them, I could not get a clear blue sky, only black.

As for low-pass anti-aliasing filters, it is true that Canon DSLRs use very strong IR-blocking anti-aliasing filters which result in long exposure times for IR photography but that has nothing whatsoever to do with whether we can capture blue sky or not. Most of my 10D & 20D IR pics did require long exposure times and can get blue skies in IR pics most of the time and very few have really dark-to-black skies. The Nikon D70 on the other hand have a weak anti-aliasing filter which does not block IR as much and therefore requires comparatively very short exposure time for IR photography but it would seem that that did not stop it from capturing black skies when the sky is really clear of clouds either.

By the way, teerex was asking if getting black skies on a clear day was camera/sensor dependent and my reply was only addressing that aspect, and not whether exposure time was affected by camera/sensor/anti-aliasing filter differences. Sadly it is a given that Canon DSLRs requires looonnng exposure times compared to other DSLRs like Nikon and even Olympus E-300.

[gooseberry]

Originally Posted by tomcat ...The Nikon D70 on the other hand have a weak anti-aliasing filter which does not block IR as much and therefore requires comparatively very short exposure time for IR photography but it would seem that that did not stop it from capturing black skies when the sky is really clear of clouds either...

I'm getting very blue skies with my D70 on cloudless days and I don't have to do much processing to get it, so that's why we wanted jonchia to post the original unedited photo.

There is ambient IR coming from the sky, but it is at a level lower than reflected IR from vegetation for example. And with the Canon camera low pass filter blocking a lot of IR out, that is probably why your skies are much darker and not as blue - since the ambient IR from the sky is not strong enough to pass the filter. So that's why I and teerex have hinted that it could be due to sensors and low-pass filters in front of the sensor.

[jonchia]

Hi everyone, thanks for chipping in to help!

Just got back from macro shoots at AMK garden with melvynyeo.

Teerex: I use a green patch of leaves for white balancing.

Gooseberry: gears are D70 with R72 and kit lens. Your eyes damn sharp!

Here's the pics without any pp.



2secs, f11.

Thanks for helping!!!