Some advice wanted

DavidWright2010 wrote:

Scottelly wrote:

?

The atmosphere doesn't change because of the focal lengths someone uses. Do you REALLY think that the 150-600mm lenses Sigma makes are so useless? REALLY? I don't know what exactly you're thinking, but a lot of people with 300mm lenses end up buying 400mm and even 600mm lenses, and they seem pretty happy with those. I know there are advantages to using shorter, better quality optics, but even 2,000 mm doesn't cut it for some subjects at even relatively short distances of 150 or 200 yards or so. On a clear, cool morning on the beach I can see pretty clearly for much greater distances than that with my naked eye, and even 300mm doesn't cut it. Later I will post some photos I have shot at less than a mile, which will show that 800mm would be more appropriate than 400mm.

One more thing. Someone interested in shooting photos of something a mile or two distant can use a camera like a P900, and it will provide far better results than even the Sigma 135mm f1.8 Art at f2.8 in an SD Quattro or SD1 Merrill, because NOTHING replaces focal length. That's why we can't just crop photos we shoot with 50mm lenses.

The idea that using a 135mm lens is "good enough" for someone who's asking about a 600mm lens just strikes me as very odd. Can you please explain how cropping a 4.7 MP photo to about 1/16 that many pixels, or about 300,000 pixels) is going to produce equivalent image quality to shooting 4.7 MP photos with a 600mm lens?

I can show you by demonstration with photos shot at 100mm and 400mm using the same zoom lens that longer focal lengths work better for capturing distant subjects in detail.

What you seem to be trying to tell us is that all those nature photographers who shoot with 600mm and 800mm lenses are wrong to do that. Are they all ignorant compared to you?

Scott-

This thread originally asked about taking good pix of object 50 km away. Some responses have given examples of pix of objects 100 m away, but that is not relevant to the OP's question.

I think the 50 mm and 135 mm FL came from my original answer, where I claimed that, for distances of 16 km and 100 km, objects near the horizon do not benefit from a 2000 mm FL - they are (usually) far too blurred by the atmosphere to make use of the longer FL, and IMO a 200 mm FL would be fine.

No one has claimed that 600 mm or longer is not useful for wildlife images of creatures a few hundred meters away.

But at sea level, across 16-20 km of water, I often see a Fata Morgana mirage. In those cases, no amount of magnification will improve the image of the distant cliff (or whatever), since what one is seeing is atmospheric distortion.

David

Well David, I think the following images demonstrate my point quite well.

Which focal length would you rather shoot a distant subject with?

Crop from 100mm shot resized to 1500 pixels across

Crop from 400mm shot resized to 1500 pixels across

Here are the original images:

100mm

400mm

Obviously the camera was able to capture more detail when the 400mm focal length was used. This bears out time and time again, no matter how far away the subject is, and even if it is literally thousands of miles away and being shot through miles of atmosphere, like the Moon. I'll say it again . . . there is no substitute for a longer focal length.

Please believe me when I say that the largest telescopes in the World, with longer focal lengths, offer better quality images of distant subjects . . . even the ones here on Earth, which have to view the sky through miles and miles of atmosphere. Do they get better image quality when the atmosphere is cleaner/clearer? Sure. I acknowledge that. But the OP was asking about long focal lengths because, like most people seeking a telephoto view, he wants to fill his frame as much as possible with the subject . . . not crop a tiny piece of an image shot at a normal focal length or a short telephoto focal length.