What focal length for 7km far away subject?

FelixPoly102

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Hello, I'm in the happy situation to see mountains out of my window. I know there are some wild animals there and I want to buy a lens to shoot them out of my window which is about 7km far away. I have an aps-c camera. Is it possible to calculate this somehow? I basically want a picture that shows about 2 meters of height in 7km distance (I hope this is not silly haha). Thanks for your help!
 
I do realise that many see this as a troll post but I don't know because I have had customers asking for things like this.

Anyway, I would like one of those people that can work the figures to come up with the focal lenght needed on a FF camera (FF just for reference) to be able to indeed capture a 2 m wide subject 7 km away. Just to see how far off my estimate is.

Where are the experts when you need them ?
 
All you really need is a 300mm lens. How, you may ask, can you use a 300mm lens for wildlife 7km away? Simple. You use a 300mm lens by going out of your house, driving the 7km to the mountains, hiking through the mountains a bit a taking pictures of the wildlife from a few meters away where there will be very little atmospheric distortion and you won't need a literal telescope to photograph them. Simple.
 
I do realise that many see this as a troll post but I don't know because I have had customers asking for things like this.

Anyway, I would like one of those people that can work the figures to come up with the focal lenght needed on a FF camera (FF just for reference) to be able to indeed capture a 2 m wide subject 7 km away. Just to see how far off my estimate is.

Where are the experts when you need them ?
https://clarkvision.com/articles/platescale/
thanks for the link but my attention span does not pass the first three lines so I am not any wiser now.

Are you ?
 
I do realise that many see this as a troll post but I don't know because I have had customers asking for things like this.

Anyway, I would like one of those people that can work the figures to come up with the focal lenght needed on a FF camera (FF just for reference) to be able to indeed capture a 2 m wide subject 7 km away. Just to see how far off my estimate is.

Where are the experts when you need them ?
Troll or not, the OP sparked some fun engaging banter. Kind of what I see forums as being at least partly for.



They might be a troll and never came back because they watched the posts pile up and got their giggles.



The other possibility is they were a new poster interested in photography who was embarrassed after the responses poking fun and never came back.
 
I do realise that many see this as a troll post but I don't know because I have had customers asking for things like this.

Anyway, I would like one of those people that can work the figures to come up with the focal lenght needed on a FF camera (FF just for reference) to be able to indeed capture a 2 m wide subject 7 km away. Just to see how far off my estimate is.

Where are the experts when you need them ?
Troll or not, the OP sparked some fun engaging banter. Kind of what I see forums as being at least partly for.

They might be a troll and never came back because they watched the posts pile up and got their giggles.

The other possibility is they were a new poster interested in photography who was embarrassed after the responses poking fun and never came back.
That came to mind and possibly is the commonest reason of why some never come back but at the same time , three pages into it and not one has posted an exact figure of what would be needed to do so.
 
I do realise that many see this as a troll post but I don't know because I have had customers asking for things like this.

Anyway, I would like one of those people that can work the figures to come up with the focal lenght needed on a FF camera (FF just for reference) to be able to indeed capture a 2 m wide subject 7 km away. Just to see how far off my estimate is.

Where are the experts when you need them ?
24mm / 2000mm * 7000m = 84m focal length

1 1/2 time the focal length of Hubble Telescope. So, with an APS-C, 56m, which is nearly the focal length of the Hubble.

Ron
 
I do realise that many see this as a troll post but I don't know because I have had customers asking for things like this.

Anyway, I would like one of those people that can work the figures to come up with the focal lenght needed on a FF camera (FF just for reference) to be able to indeed capture a 2 m wide subject 7 km away. Just to see how far off my estimate is.

Where are the experts when you need them ?
24mm / 2000mm * 7000m = 84m focal length

1 1/2 time the focal length of Hubble Telescope. So, with an APS-C, 56m, which is nearly the focal length of the Hubble.

Ron
So mounting an APS C camera on that scope will do the trick.

But , how is the IQ of that telescope on land ?

Any photos of the sort of bokeh one would expect ?

Does it give 3D Pop ?

1e2b9c986dc54a04b3cf49d92229874d.jpg
 
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Try Nikon P1000 first

I have an older model P900 and this is what I could get with it

Have fun



--
Old Greenlander
"I show the world the way I see it"
40 years of photography and still learning
 
I do realise that many see this as a troll post but I don't know because I have had customers asking for things like this.

Anyway, I would like one of those people that can work the figures to come up with the focal lenght needed on a FF camera (FF just for reference) to be able to indeed capture a 2 m wide subject 7 km away. Just to see how far off my estimate is.

Where are the experts when you need them ?
24mm / 2000mm * 7000m = 84m focal length

1 1/2 time the focal length of Hubble Telescope. So, with an APS-C, 56m, which is nearly the focal length of the Hubble.

Ron
So mounting an APS C camera on that scope will do the trick.
Of course, but you'll need one hell of a tripod!
But , how is the IQ of that telescope on land ?
The lenses were designed for the refractive index from vaccum to glass. I have no Idea how it would affect the optics other than having to change the relative positions of the second mirror relative to the primary.
Any photos of the sort of bokeh one would expect ?
Donut bokeh, there's a secondary mirror.
Does it give 3D Pop ?
What the hell are-you talking about? The only thing that gives cues to the brain that there are textures in a monoscopic image is shadows. These mirror lenses suffer from lower contrast when compared to refractive optics. So, it is unlikely that it will have the high contrast that will help your brain understand the 3D features of the image.
 
Does it give 3D Pop ?
What the hell are-you talking about? The only thing that gives cues to the brain that there are textures in a monoscopic image is shadows. These mirror lenses suffer from lower contrast when compared to refractive optics. So, it is unlikely that it will have the high contrast that will help your brain understand the 3D features of the image
Perhaps the animals could wear hi-vis jackets? ;-)
 

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