Failed, shooting the sun

[pwm2]

You normally always have to make lenses that can focus past infinity.

One reason is that the lens is affected by production tolerances and by temperature. So each individual lens must manage infinite focus at the full temperature range for the full lifespan of the lens.

But an even more important thing is that with AF lenses, you want the camera to be able to place the focus on either side of perfect for the full range. I.e. you don't want any special corner cases where the camera must handle infinite focus differently just to avoid slamming into the end limit of the lens. Especially since the camera may need to perform a bit of hunting if the subject have low contrast or contains very small features making the AF system see multiple potential solutions.

One thing to note about lenses and the sun is that 45° sounds like much but only reduces the front area of the lens with 30%. So significant amounts of energy will still enter the lens - just that we do not know how much of that energy that will be focused somewhere inside the lens or focused at the camera.

[Gary McDuffie]

Yes to both questions. However, the 100-400 doesn't go nearly as far beyond inf.

I'm still working on the theory now that perhaps there is an overexposure situation at a wavelength that is not being seen or registered in metering or histogram somehow.

Thanks for all of the discussion. I'll keep working on it, but I think I'm going to order a real filter to play with.

[Gary McDuffie]

Originally Posted by pwm2

You normally always have to make lenses that can focus past infinity.

One reason is that the lens is affected by production tolerances and by temperature. So each individual lens must manage infinite focus at the full temperature range for the full lifespan of the lens.

But an even more important thing is that with AF lenses, you want the camera to be able to place the focus on either side of perfect for the full range. I.e. you don't want any special corner cases where the camera must handle infinite focus differently just to avoid slamming into the end limit of the lens. Especially since the camera may need to perform a bit of hunting if the subject have low contrast or contains very small features making the AF system see multiple potential solutions.

Good points.

Originally Posted by pwm2

One thing to note about lenses and the sun is that 45° sounds like much but only reduces the front area of the lens with 30%. So significant amounts of energy will still enter the lens - just that we do not know how much of that energy that will be focused somewhere inside the lens or focused at the camera.

For one thing, with the length of the lens shade on the 100-400, there isn't going to be much there. And, this goes well beyond paranoia. People aim their cameras at the sun all the time when they shoot people back-lit and worse. Granted, the sun is usually low when that happens, and a lot of the energy has been attenuated. But, you get the idea.