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A place to politely discuss the tools, technique and culture of photography.

This is not a good place to simply share cool photos/videos or promote your own work and projects, but rather a place to discuss photography as an art and post things that would be of interest to other photographers.

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Let's Discuss Focal Lengths Beyond 150mm (alien.top)

submitted 10 months ago by billingsley@alien.top to c/photography@viewfinder.pro

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At what point does longer focal length no longer matter? I want to take photos of things far away, like across the street.

I would do a camera test if I still owned my 70-300 Canon kit lens but I don't. Right now the longest focal length I own is a 24-70 for my Sony.

I remember about that lens, once I got out past 150-175m, it seemed like the FOV was just cropping in more rather than actually feeling closer to the subject. But that was a cheapo kit lens that had a terrible reputation. Does that just apply to cheap lenses or do more expensive lenses have more magnification?

Is there really a significant difference between 300, 400 and 600m lenses? Of course I have no physical access to any such lenses at the moment.

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[–] ApatheticAbsurdist@alien.top 1 points 10 months ago (1 children)

it seemed like the FOV was just cropping in more rather than actually feeling closer to the subject.

Yes that's what changing the focal length of any lens does. It enlarges the image so that a smaller portion the image fills the sensor (the rest is effectively cropped out). The only difference is if you were to take a photo with a 300mm lens and then took one with a 150mm lens and cropped it to match the 300mm, and then took one with a 75mm and took that and cropped it, you'd still have the full resolution on your 300mm shot, your 150mm shot would be much smaller, and your 70mm shot would be tiny with very little detail.

You should see the same effect if you shoot something with your 24-70mm at 24mm vs 70mm.

More expensive lenses will be sharper. I'm certain if you compared your canon 70-300mm at 70mm vs your Sony 24-70 at 70mm, the Sony would probably be noticeably sharper, and I think that canon got worse at longer lengths.

And also you can hit diffraction, if you shoot at f/11 or smaller (f/16, f/22) that diffraction will further soften the lens. So shooting at f/5.6 to f/8 will be better, but if the lens is crap and soft at f/5.6, that doesn't help you as much.

Finally, there is atmospheric haze. If something is very far away, there is just a softness in the atmosphere from different factors from smog to mirage heat that can further soften your image.

[–] Bishops_Guest@alien.top 1 points 10 months ago

There is a flattening effect of focal length, but it comes from changing your preferred working distance rather than an optical effect. If you take a picture of someone at 10 feet with a 20mm and an 85mm then crop in the 20mm picture it will look the same. However, if you fill the frame with a persons face with a 20mm and then with an 85mm by foot zoom you’ll get different pictures due to the change in the ratio of distance to the lens.

If you have something 1 Unit wide and it’s 1 Unit away from you, then you move it so it’s 2 units away from you then it goes from taking up 60 degrees of your field for view to 28.96 degrees. However, if it starts at 10 units away then moving it one more unit goes from 5.7 degrees to 5.2 degrees. So yes, it is just cropping, and not distortion but it still changes the look of the photo by changing the effect of distance on relitive size in the final image in a lot of typical uses.

You can see the same thing in huge murals of people: from a distance they look like normal propotions, but when you get close and at an angle they start to look really weird because the relative distance between parts of the painting is different than how we’re used to seeing people.