![optics - How can I increase the flange focal distance (back focal length) of DSLR lens? - Photography Stack Exchange optics - How can I increase the flange focal distance (back focal length) of DSLR lens? - Photography Stack Exchange](https://i.stack.imgur.com/jvzLX.png)
optics - How can I increase the flange focal distance (back focal length) of DSLR lens? - Photography Stack Exchange
![Universal method for determining the focal length of optical systems by moire deflectometry. | Semantic Scholar Universal method for determining the focal length of optical systems by moire deflectometry. | Semantic Scholar](https://d3i71xaburhd42.cloudfront.net/3efb95681f7b4958d98e3d97ad26c940fc532203/2-Figure2-1.png)
Universal method for determining the focal length of optical systems by moire deflectometry. | Semantic Scholar
Alternative method for measuring effective focal length of lenses using the front and back surface reflections from a reference plate
![15: Lens L1 and L2 is beam expander. L1 has a front focal length FFL of... | Download Scientific Diagram 15: Lens L1 and L2 is beam expander. L1 has a front focal length FFL of... | Download Scientific Diagram](https://www.researchgate.net/publication/269706704/figure/fig18/AS:652580606734354@1532598749430/Lens-L1-and-L2-is-beam-expander-L1-has-a-front-focal-length-FFL-of-125mm-and-back.png)