Bvanant,
Thanks for your remarks. You are right that calculations are based in FF. I should include an input for sensor size or crop factor. I will think about the best / easier way to include it
For Macro lens is a different thing or I think it is. I had put a note in earlier versions of the calculator that it would not work for macro lens. I took it away later car I was not so sure, but your remark makes me rethink the reason. Optically, Focal Lenght of a lens will have a particular angle of view. Angle of view at MFD will determine magnification, which at the same time will be larger on a crop sensor as part of the image (light) will not hit the sensor and the ratio Object size : image size will be different than in a FF sensor.
But lens assemblies are fabricated differently and lens placed differently in the barrel, in cases emulating the use of a extension tube and then producing a higher magnification for the same focal lenght.
Macro lenses are fabricated and assembled in a way allowing a closer MFD and this distorts the results in the calculation.
For macro lens the more correct approach to calculate new magnification with diopters attached would be using native magnification (as per manufacturers specification), not MFD. And in this case I am prone to think that crop factor will have no incidence but I am not quite sure how lens' manufacturers indicate the native magnification in the case of APS-C especific lens.
I do not exclude to use this sort of approach.
Using this more appropiate method for macro lens, your 60mm macro + 10 diopter filter will result in 2.2X
----
For better understanding of the calculator, for those interested in perfect it, like you, I detail below the concepts / formulas used in the calculator.
1) Diopters changes the focusing distance of lens when set to infinity focus. The focus distance of a diopter = 1000mm by diopter strength/ power. For example, my Inon +6 diopter filter has a focus distance of 165 mm (rounded) result of 1000/6.
Note: A lens set at infinity focus will focus at the the diopter's focus length, no matter what is the FD of the lens to which is attached.
2) the MFD of a lens + diopters combination is dependant of the adition of diopter of the lens (to be calculated) plus diopter(s) attached.
3) Diopter power of a lens = 1000 divided by MFD of the lens in mm. For example, Sony FE 85mm F1.8 has a MFD of 800 mm, so its diopter power is 1000/800 = +1.25
4) New MFD = 1000 divided by total diopters (lens' s + diopters). In the case of this Sony lens + Inon +6 diopter total diopter = +7.25. So new MFD = 1000 / 7.25 = 138 mm
5) New magnification of the lens + diopter filter(s) is the result of the total diopter of lens plus diopter filter(s) multiplied by the focal length of the lens in meters. In this example: 7.25 * 0.085 = 0.62x
6) For Working range I took the new MFD as the closest point and the Focal lenght of the diopter attached as the farthest since diopter filters will not focus beyond its focal lenght.
Notes:
a) results will be always estimations as lens are usually manufactured differently.
b) I am not a "scientist" just an amateur and mostly autodidact photograher, so erreurs may exist.
Welcome everybody to perfect this calculator if considered handy and useful.
regards
