FA 50 1.4 vs DA 50 1.8

ogl wrote:

Bernie3 wrote:

I have the FA 50 f/1.4 and K5IIs and plan to stick with APC. I could sell the FA 50 and purchase a DA 50 f/1.8. Would the DA 50 f/1.8 be better? Is the DA sharper edge to edge?

Bernie

I had FA50/1.4 for many years and I have DA50/1.8. DA50/1.8 is sharper at all apertures.

It's better than FA50/1.4 in terms of sharpness. FA43 is sharper than FA50/1.4 too.

If you like f/1.4-1.6's bokeh only, keep it...But I don't need soft pictures with such bokeh.

I'm not fan of such fast lenses. 1.8 is enough for me.

I agree with you that most lenses faster than f/2 need to be stopped down by at least half a stop to be adequately sharp and free of bloom. You also end up with considerable failure to capture all the light due to incidence angle of light at fast apertures.

However, at least on the older model f/1.4s (m50 in my case), the speed of the lens does benefit comparatively when stopped down somewhat. The sharpness at f/2 is pretty good. However, the f/1.8 is still practically wide open at f/2 - and some bloom is still evident. Also, longitudinal CA (purple in front, green behind point of focus) is much more evident.

The lenses are pretty close to equal overall, but their strengths differ. It isn't surprising that the newer, designed for crop sensor, lens will be a bit sharper at most apertures. However, for fast aperture shooting (f/2.4 and faster), the f/1.4s are probably at least as good.

Bottom line, if I had an FA and was happy with it, I wouldn't look at the DA f/1.8. However, the m50 is not a FA - and I like having the AF option and better metering options.