DLS Posted September 30, 2015 Share #1 Â Posted September 30, 2015 Advertisement (gone after registration) I realize this may a dumb question but here goes: when using a 2x APO extender with a 280/f4 I lose two stops, correct? Â But what does this mean for the actual setting on the lens itself, e.g., when it indicates f/4, is it really f/8, and when f 5.6, really f/11 --- OR --- does moving the setting on the lens have no impact UNTIL you reach the 2 stop difference, meaning that there is no impact when lens is at f/4 or f/5.6...I only ask because the EXIF data provided by an M240 is a guess in any case and can be all over the place. Thanks for any insight you can provide. Link to post Share on other sites More sharing options...
stuny Posted September 30, 2015 Share #2  Posted September 30, 2015 Whatever setting you have on your lens by adding the 2X extender you will have two stops less light available. The f/stop itself does not change, only the amount of light reaching the sensor or film. Link to post Share on other sites More sharing options...
wildlightphoto Posted September 30, 2015 Share #3 Â Posted September 30, 2015 The effective aperture is reduced by two stops in all cases. Â For example when the lens aperture is set at f/4, the effective aperture for the lens + extender is f/8. Â When the lens is set at f/5.6, the effective aperture for the combination is f/11. Link to post Share on other sites More sharing options...
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