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04-04-2008, 01:22 PM   #1
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Telephotolens tryout, go ahead and boast.

Would some people be intrested in leaning out the window and take a picture of some people say, 100m-200m away with their longest focal lengths and post the results?

I am about to have two challenges this summer. First I am going to be taking photos on concerts here. And it seem I will be able to join and take photos of some explosive trainings for a bombunit.

Niether of these will let me closer then 100m-200m though. The second I might have to be as long as 400 meters away. Are there any chance of getting any good results when it comes to people shots? Will I even be able to see what they look like? I only have a 200mm lense and this is what a crow looks like 400m away with it.

Crow

04-04-2008, 01:36 PM   #2
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A 200mm lens should give you a ratio of about 1:7 for 'picture width':distance on a crop sensor camera.

That would be 70m distance results in a 10m wide image @200mm focal length.
Or 210m in a 30m wide image. And with a 300mm lens, it should be around 20m wide. And so on.

You can easily find out by yourself. Just take a shot of something, say, 10m away. Then watch the image and estimate how many meters you have covered in width or height.
This ratio stays constant for what ever distance you are shooting at for a given focal length.

Or, well, just take a picture of a ruler ...

Of course, sharpness is a different thing ... If your crow isn't sharp, nothing else will be ... I guess.

Last edited by Noisychip; 04-04-2008 at 01:43 PM.
04-04-2008, 01:50 PM   #3
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As a simple calculation, with any lens for relitively distant subjects

Image size = Object size x focal length / Object distance

Consider a person 2 meters high (about 6'7") 400 meters away, with a 400mm lens (0.4meters)

your image is 2mm high on a 24mm x 16 mm sensor (ASP-C sensor size) or with a horizontal format about 1/8 of the frame height.

On the K10D that makes the entire person 324 pixels high or each pixel is 6 mm (about 1/4 inch in terms of the subject)
04-04-2008, 02:02 PM   #4
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But calculations are not as fun as seeing results from peoples lenses . No calculations will show what lenses makes good results

But thanks for the answers, don't want to sound ungrateful, because I am not.

So with a 2x TC and a 400mm lens a 2m person would take up about 640px height? Thats not too bad, for internet usage, but what will the quality be?

04-04-2008, 03:38 PM   #5
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QuoteOriginally posted by Zewrak Quote
But calculations are not as fun as seeing results from peoples lenses . No calculations will show what lenses makes good results

But thanks for the answers, don't want to sound ungrateful, because I am not.

So with a 2x TC and a 400mm lens a 2m person would take up about 640px height? Thats not too bad, for internet usage, but what will the quality be?
No offence taken. the reason to give you the calculation is so that you can better plan what lenses you need.

with the data I gave you, take any image you have of a person standing at a height of 1/8 to 1/4 of the frame and look at the quality.

As long as you have a good lens and are focused and hold the lens still you should be OK.

one thing I have noticed however is that when things are that far away, and the object so small, sometimes vibration and camera shake causes you to move the focusing sensor off subject and focus is off because iot is picking up something else
04-04-2008, 04:10 PM   #6
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QuoteOriginally posted by Lowell Goudge Quote
No offence taken. the reason to give you the calculation is so that you can better plan what lenses you need.

with the data I gave you, take any image you have of a person standing at a height of 1/8 to 1/4 of the frame and look at the quality.

As long as you have a good lens and are focused and hold the lens still you should be OK.

one thing I have noticed however is that when things are that far away, and the object so small, sometimes vibration and camera shake causes you to move the focusing sensor off subject and focus is off because iot is picking up something else
Well I wont be fiddling with any fast moving objects. Except for explosions . And I will be able to use very stationary tripods and stuff, so the stability will be as good as it can be. Im thinking manual focusing and a heavy tripod and possibly mirror up shooting.

Anyways, won't light start to fall off quite drastically at that distance though, can I really expect the same sharpness as a photo taken with a 50mm with your calculations? Shouldnt there be more information into the equation?

What lenses could pull this off? A Bigma? Or do i need a bigger aperture? Lets say for the sake of argument that I want to take a picture at 300 meters distance on people kneeling down and fiddling with wires and stuff. Are there any lenses good enough to really be able to pick up enough light to get the details going, not considering the size of the people.
04-04-2008, 05:02 PM   #7
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How long are you looking for? There are lenses like the Tamrom SP 500 f/8 mirror. They do produce odd, donut like bokeh and are somewhat difficult to focus. But it's hard to beat a mirror's value.
04-04-2008, 07:44 PM   #8
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QuoteOriginally posted by Zewrak Quote
Well I wont be fiddling with any fast moving objects. Except for explosions . And I will be able to use very stationary tripods and stuff, so the stability will be as good as it can be. Im thinking manual focusing and a heavy tripod and possibly mirror up shooting.

Anyways, won't light start to fall off quite drastically at that distance though, can I really expect the same sharpness as a photo taken with a 50mm with your calculations? Shouldnt there be more information into the equation?

What lenses could pull this off? A Bigma? Or do i need a bigger aperture? Lets say for the sake of argument that I want to take a picture at 300 meters distance on people kneeling down and fiddling with wires and stuff. Are there any lenses good enough to really be able to pick up enough light to get the details going, not considering the size of the people.
I have a 1000mm celestron C90 spotting scope with a T Mount

works out to F11

bump the ISO up a little and your 2 meter man at 400 meters becomes 1cm on the sensor or 5/8 the height of a frame.

Just make sure your stable. it is really sensitive to vibration. not only do you need a stiff tripod, but hang your camera stuff from it to weigh it down

As long as you are v

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