OR120 Posted January 21, 2024 Share #81 Posted January 21, 2024 Advertisement (gone after registration) 1 minute ago, erl said: Sometimes, in some situations, you are right, but the original debate was about differences between moving your feet or changing lenses, both of which produce a totally different outcome. If 'timing' is the issue, which it can be, then the whole criteria shifts. sorry, sometimes I lose track of what the topic really is.................. 1 Link to post Share on other sites More sharing options...
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erl Posted January 21, 2024 Share #82 Posted January 21, 2024 4 hours ago, OR120 said: sorry, sometimes I lose track of what the topic really is.................. So do I! Link to post Share on other sites More sharing options...
otto.f Posted January 21, 2024 Share #83 Posted January 21, 2024 On 1/17/2024 at 10:55 PM, erl said: Using your feet produces an optically different effect from using a different focal length 8 hours ago, erl said: Remember that 'perspective' is only a function of your 'feet'. Not the lens. This is not true, at least not consistent. The perspective lines of a building shot with an 18mm are more oblique than those from a 24mm if you walk back with the latter to get the same width of image. Link to post Share on other sites More sharing options...
M11 for me Posted January 21, 2024 Share #84 Posted January 21, 2024 vor einer Stunde schrieb otto.f: This is not true, at least not consistent. The perspective lines of a building shot with an 18mm are more oblique than those from a 24mm if you walk back with the latter to get the same width of image. ??? Link to post Share on other sites More sharing options...
chris7273 Posted January 21, 2024 Share #85 Posted January 21, 2024 Some examples here : perspective / focal length / distance https://exposuretherapy.ca/photography-guide/perspective-and-camera-position/ 1 2 Link to post Share on other sites More sharing options...
M11 for me Posted January 21, 2024 Share #86 Posted January 21, 2024 vor 2 Stunden schrieb chris7273: Some examples here : perspective / focal length / distance https://exposuretherapy.ca/photography-guide/perspective-and-camera-position/ Interesting site. Link to post Share on other sites More sharing options...
IkarusJohn Posted January 21, 2024 Share #87 Posted January 21, 2024 Advertisement (gone after registration) 5 hours ago, otto.f said: This is not true, at least not consistent. The perspective lines of a building shot with an 18mm are more oblique than those from a 24mm if you walk back with the latter to get the same width of image. If you move your feet, the perspective changes. 2 1 Link to post Share on other sites More sharing options...
M11 for me Posted January 21, 2024 Share #88 Posted January 21, 2024 vor 34 Minuten schrieb IkarusJohn: If you move your feet, the perspective changes. Herewith I agree. In camera zoom does not change the perspective. 1 Link to post Share on other sites More sharing options...
IkarusJohn Posted January 21, 2024 Share #89 Posted January 21, 2024 15 minutes ago, M11 for me said: Herewith I agree. In camera zoom does not change the perspective. That’s true. I don’t think anyone suggested that. Link to post Share on other sites More sharing options...
M11 for me Posted January 21, 2024 Share #90 Posted January 21, 2024 vor 4 Minuten schrieb IkarusJohn: That’s true. I don’t think anyone suggested that. That's possible but that is what I understood from post 85 and others. But I understand now. Thank you. 1 Link to post Share on other sites More sharing options...
erl Posted January 21, 2024 Share #91 Posted January 21, 2024 11 hours ago, otto.f said: This is not true, at least not consistent. The perspective lines of a building shot with an 18mm are more oblique than those from a 24mm if you walk back with the latter to get the same width of image. With respect, I think you are confusing 'convergence' with 'perspective'. 1 Link to post Share on other sites More sharing options...
otto.f Posted January 22, 2024 Share #92 Posted January 22, 2024 8 hours ago, erl said: With respect, I think you are confusing 'convergence' with 'perspective'. That could be my limited English then 1 Link to post Share on other sites More sharing options...
erl Posted January 22, 2024 Share #93 Posted January 22, 2024 2 hours ago, otto.f said: That could be my limited English then Don't apologize for limited English, if it is not your native tongue. Aside from English my limits on all other languages is zero. I admire anyone who s multilingual. 4 Link to post Share on other sites More sharing options...
Harpomatic Posted January 22, 2024 Share #94 Posted January 22, 2024 On 1/19/2024 at 11:46 PM, IkarusJohn said: The assumption in cropping (particularly in camera) is that the central area of an image is the same regardless of focal length - so, if you take an imgae with a 21mm lens and crop the centre, you can get the same image, including depth of field, as if you took the image with a 90mm lens. You don’t. Actually, you do. It’s not an assumption, it’s optics. If you take the image from the same spot, same subject in the centre, with a 21mm and a 90mm (to follow your example), you get exactly the same perspective and DOF at same aperture. Just a lot less resolution on the crop from the 21mm obviously! If you crop off centre it’s different. This is why, no matter what a lot of people say about crop cameras and the equivalence in lenses, an APS-C 35mm lens will have EXACTLY the same perspective as a 52.5mm on full frame. The DOF will change because you are using a different focal length at the same distance. 1 Link to post Share on other sites More sharing options...
M11 for me Posted January 22, 2024 Share #95 Posted January 22, 2024 We have to think in "equivalence". When we adapt the aperture then we have the same DOF. Link to post Share on other sites More sharing options...
IkarusJohn Posted January 22, 2024 Share #96 Posted January 22, 2024 (edited) 6 hours ago, Harpomatic said: Actually, you do. It’s not an assumption, it’s optics. If you take the image from the same spot, same subject in the centre, with a 21mm and a 90mm (to follow your example), you get exactly the same perspective and DOF at same aperture. Just a lot less resolution on the crop from the 21mm obviously! If you crop off centre it’s different. This is why, no matter what a lot of people say about crop cameras and the equivalence in lenses, an APS-C 35mm lens will have EXACTLY the same perspective as a 52.5mm on full frame. The DOF will change because you are using a different focal length at the same distance. Perspective, in the centre crop, the rest, no. Too much going on. Compression, depth of field, resolution and lens characteristics. You do get the same field of view, but that’s pretty much it. Your APS-C observation pretty much confirms the point. I guess we have to agree to differ on the point. Edited January 22, 2024 by IkarusJohn Link to post Share on other sites More sharing options...
jaapv Posted January 22, 2024 Share #97 Posted January 22, 2024 8 hours ago, Harpomatic said: Actually, you do. It’s not an assumption, it’s optics. If you take the image from the same spot, same subject in the centre, with a 21mm and a 90mm (to follow your example), you get exactly the same perspective and DOF at same aperture. Just a lot less resolution on the crop from the 21mm obviously! If you crop off centre it’s different. This is why, no matter what a lot of people say about crop cameras and the equivalence in lenses, an APS-C 35mm lens will have EXACTLY the same perspective as a 52.5mm on full frame. The DOF will change because you are using a different focal length at the same distance. Plus, cropping to the center is exactly the same as mounting a longer lens you stay in the optical axis. 1 Link to post Share on other sites More sharing options...
jaapv Posted January 22, 2024 Share #98 Posted January 22, 2024 2 hours ago, IkarusJohn said: Perspective, in the centre crop, the rest, no. Too much going on. Compression, depth of field, resolution and lens characteristics. You do get the same field of view, but that’s pretty much it. Your APS-C observation pretty much confirms the point. I guess we have to agree to differ on the point. Compression is a function of distance, not focal length, John 1 Link to post Share on other sites More sharing options...
IkarusJohn Posted January 22, 2024 Share #99 Posted January 22, 2024 2 hours ago, jaapv said: Compression is a function of distance, not focal length, John Circular, Jaap. Too many variables to be proven. Now, I’m sure you will say, as I recall you’ve said before, that if the camera doesn’t move, a crop of the centre of a 35mm image will be identical to an image taken with a 50mm lens at the same aperture, including depth of field. Rinse and repeat. I will continue to enjoy my primes, resisting the assurances that in camera cropping is the future! Link to post Share on other sites More sharing options...
jaapv Posted January 22, 2024 Share #100 Posted January 22, 2024 Don’t we all wish that we were resisting future whilst being forced to embrace it? 1 Link to post Share on other sites More sharing options...
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