Question on focal length?

[mikoh4792]

These are just quick shots I took with my 105mm lens to see how close I could get. I'm wondering if there is a way, or any programs I can use to see how much I would be zoomed in if I shot this at 200, 300, 400..etc mm.

 

[480sparky41 40]

If you do some simple math, you can get a good idea of the FOVs.

If you're shooting with a 105mm lens, and want to see what a 200mm would look like, just take the pixel dimensions of the image and divide them by 200, then multiply by 105. Then crop your image to those dimensions.

For instance, if your original image is 4000 x 3000 pixels, 4000/200*105 = 2100 and 3000/200*105 = 1575. Now crop your image to 2100x1575 pixels.

300mm? 4000/300*105 and 3000/300*105 gives you 1400x1040

400mm: 4000/400*105 and 3000/400*105 gives you 1050x788.

There are also smartphone apps where you can enter the subject frame (size in inches or feet), size type of camera (crop, full-frame) and your distance, and it will calculate the fl needed.

 

[mikoh4792]

If you do some simple math, you can get a good idea of the FOVs.

If you're shooting with a 105mm lens, and want to see what a 200mm would look like, just take the pixel dimensions of the image and divide them by 200, then multiply by 105. Then crop your image to those dimensions.

For instance, if your original image is 4000 x 3000 pixels, 4000/200*105 = 2100 and 3000/200*105 = 1575. Now crop your image to 2100x1575 pixels.

300mm? 4000/300*105 and 3000/300*105 gives you 1400x1040

400mm: 4000/400*105 and 3000/400*105 gives you 1050x788.

There are also smartphone apps where you can enter the subject frame (size in inches or feet), size type of camera (crop, full-frame) and your distance, and it will calculate the fl needed.

Thanks! That helped a lot.