With the same FL and f-number, a DX lens has more light covering the APS-C area?

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mxk7 Forum Member • Posts: 63
With the same FL and f-number, a DX lens has more light covering the APS-C area?
2

Am I right on this?

The amount of light passing through the aperture should be the same with a given FL and f-number, no matter how big the senor is. As an FX lens needs to cover a larger sensor area, the "intensity" of the light reaching the sensor is smaller when compared with a DX lens with the same FL and f-number.

If only part of the full-frame sized sensor is used for imaging, like in the DX crop mode, then the FX lens will have slightly more than the one-stop loss in its max aperture?

I am asking this because I think of using DX telephoto lenses on my Z7 for better portability, price, and effective FL. I know the effective FL thing is basically the same as cropping the image. I am fine with cropping, or say only using part of the sensor, for telephotography if this can save me a lot of money on the lenses and the efforts to carry them. The FLEXIBILITY offered by the high MP full-frame sensor is the main reason I got a Z7. It seems that the light gathering ability is another advantage of a DX lens over a similar FX lens in DX crop mode.

I really like the compatibility of the DX/FX lens on DX/FX bodies, a lot of freedom. I may get a second Z DX body for a two-body setup.

 mxk7's gear list:mxk7's gear list
Nikon Z7 Fujifilm X-T200 Fujifilm XF 55-200mm F3.5-4.8 R LM OIS Fujifilm 15-45mm F3.5-5.6 OIS PZ Nikon Z 24-70mm F4 +1 more
Nikon Z7
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