Fast Aperture, Good Light

I mentioned yesterday that I used a three stop neutral density filter in order to be able to use my 50mm f/1.4L VCM lens at f/1.4. The photo below is my favorite from that shooting.

A neutral density filter is tinted glass that reduces the light reaching the camera. This is needed in good light to shoot at the widest apertures because of limits on a camera's shutter speed. My camera has a 1/8000th of a second fastest shutter speed. Many excellent cameras only have shutters half as fast.

Fast is a confusing word when it comes to exposure. With shutter speeds it means shorter exposures and less light. With apertures it means wider openings and more light.

An f-stop of 1, or f/1, means the diameter opening of the aperture equals the focal length of the lens. A 50mm lens at f/1 would have an aperture opening of 50mm. The f-stop progression in full stops is 1, 1.4, 2, 2.8, 4 , 5.6, 8, 11, 16, 22, etc. Each stop lets in half as much light as the one before.

Back to the need for the ND filter, without the filter the exposure for the photo below would have been 1/12000th of a second, which is beyond the capabilities of my camera's mechanical shutter, so it would be over exposed. [Electronic shutter mode is another matter but my camera only offers faster shutter speeds in manual or shutter priority modes, not aperture priority which is how I shoot.]

Why the fast aperture of f/1.4? The aperture determines the depth of the area in focus, the degree of "blurriness" in the out of focus areas, and the quality of "blur" in the out of focus areas. A wide open aperture is completely round with no aperture blades narrowing the opening so the "blur" or "bokeh" is at it's best. 

The quality of bokeh in each lens will be different but the quality of bokeh in each lens will generally be best at its widest aperture. If I had the RF 50mm f/1.2 lens I would want to use f/1.2 for these purposes. 

If you click on the photo, then click on it again, blogger will, for some reason, blow it up beyond 100%. 

RF 50mm f/1.4L VCM, f/1.4, 1/1500 sec., ISO 100
3 stop ND filter