[BasilG]

They might individually have less energy, but there are an awful lot of them. Total energy received is still significant.

 

I suggest having a look at a solar emission spectrum.

[frank]

According to Wiki: Sunlight at the top of Earth's atmosphere is composed (by total energy) of about 50% infrared light, 40% visible light, and 10% ultraviolet light.

[frank]

And here is the solar spectrum (from http://www.globalwarmingart.com/wiki/Fil...trum_png):

 

[miro]

BrightColour – I realy like picture #2. Wonderful composition lighting,colours, details. I have look at this picture and enjoy it it a lot. Thanks for sharing.

 

I have some taught about spectrum

1. sun spectrum before entering atmosphere.
   
2. Transfer function of air – it is dependant of time of the day. I assume that you shooting early in the morning or late evening. Not pointing out the camera vertical to sky at 12:00AM and searching the space shuttle. :-)
   
3. Transfer function of lens. – not very important, since the most attenuation comes from air
   
4. Transfer function of IR and colour filters.
   
5. Last but not at least – transfer function of Silicone /sensor/.  Silicon gap is equally high as IR photons. That is why silicone detectors are best in IR spectrum. Just think how good is jour TV IR remote control.
   

[miro]

My feeling /not scientific/ is that IR will not damage jour camera but IR will electrically saturate the CMOS/CCD sensor. making strange looking images

[frank]

My feeling /not scientific/ is that IR will not damage jour camera but IR will electrically saturate the CMOS/CCD sensor. making strange looking images

Thank you for your input, miro. I remember sometime ago there was a post here which showed that the shutter curtain of a camera was burned out (maybe) by the Sun. So I put up this post to ask for advises for avoidong this to happen.

[frank]

I don't think so. The main purpose is to limit the amount of direct sunlight entering through the lens. A telephoto lens has a bigger physical aperture size than a wide-angle lens. So at the same F-stop, you'll let more light enter the system with the telephoto lens - which is the main worry here.

I don't think so. What matters here is the solid angle of the lens to the sensor, not the diameter size of the lens element. At the same F-stop a tele lens has the same solid angle as a wide lens to a point on the sensor. But for a tele lens the light ray will hit the sensor more likely with a straight angle.

[BasilG]

I don't think so. What matters here is the solid angle of the lens to the sensor, not the diameter size of the lens element. At the same F-stop a tele lens has the same solid angle as a wide lens to a point on the sensor. But for a tele lens the light ray will hit the sensor more likely with a straight angle.

 

I don't quite understand what the problem is here. Switch on a strong light bulb, shoot it with a wide-angle, then take your longest tele lens, shoot the light bulb from the same distance using the same f-stop and exposure time (!) and check which one comes out brighter. When aiming at a point light source, the telephoto will let much more light enter the system than a wide-angle, which is why shooting the mid-day sun with a telephoto is dangerous for your eyes. No?

[frank]

I don't quite understand what the problem is here. Switch on a strong light bulb, shoot it with a wide-angle, then take your longest tele lens, shoot the light bulb from the same distance using the same f-stop and exposure time (!) and check which one comes out brighter. When aiming at a point light source, the telephoto will let much more light enter the system than a wide-angle, which is why shooting the mid-day sun with a telephoto is dangerous for your eyes. No?

Yes, it is true that at the same F-number and the same exposure time, the sensor collects more energy from the Sun for the tele lens. But the energy spreads over a larger area on the sensor. The energy received per unit area on the sensor is the same, providing that the incident angle of photons are the same.