[Flickeroo]

How to do a lens test:

1) Set up your tripod with a far away background and some stationary object close by.
2) Focus and shoot lens A on the stationary object wide open, at f4, and at f8.
3) Focus and shoot lens B on the stationary object wide open, at f4, and at f8.
4) Remember to keep white balance fixed (do not use AWB).
5) Use a proper hood.

Now you are done! Compare each lens at each aperture and see what you like best.

EDIT: No guarantee that this will help you much... I tried to figure out if I should sell the K 55 1.8 or the A 50 1.7, and i simply could not pick a favorite because they are both different enough! Gah!

I'll follow your instructions during the weekend. I might be able to tell if there's a difference. Thank you for the WB tip. I might set everything on manual in order to make sure that everything remains the same.

[audiobomber]

I'll follow your instructions during the weekend. I might be able to tell if there's a difference. Thank you for the WB tip. I might set everything on manual in order to make sure that everything remains the same.

I would leave the WB on auto, assuming that's how you intend to use the lens. I prefer to let the camera set the exposure too, since different lenses may expose differently. I like to make my test mimic reality as much as I can. For resolution testing though, always a tripod and 2s MLU.

If you decide to post your results, which is always welcome around here, be prepared for a lot of critique. No matter what settings you use, someone will think you should have done something different.

[paperbag846]

I would leave the WB on auto, assuming that's how you intend to use the lens.

I suggest to keep the WB fixed so that you can see any differences in how the lens' render colours. While it might be further away from "real" shooting, the trick here is to control variables to elucidate any differences between the two lenses.

[bdery]

Some on this board say the 1.7 is sharper at 1.8, but the only objective test I've seen found otherwise. Nifty 50 Shootout ERPhotoReview Maybe the people who preferred the 1.7 didn't use a hood, maybe they confused contrast with resolution, or quite possibly their copy was sharper. Most who say the 1.7 is sharper are just parroting someone else. In a test dgaies posted showing the two, most thought the 1.7 sharper and some (like me) found the opposite. One thing for sure, they are both great lenses, so you can't lose.

I fully agree with the last sentence.

However, I disagree with the rest. It's nickpicking, since indeed both lenses are great, but being an optical designer I know some stuff about contrast, sharpness, MTF, and all those other buzzwords we love On my K20D, my f1,4 was clearly less sharp AND less contrasty at f1,8 than my f1,7 wide open. Could it be anecdotal? Sure. But I think considering the sheer number of people observing the same thing, it's more than parrotting.

I still have sample shots even though I don't own the f1,4 anymore, I could show them to you if you'd like.

[dgaies]

Some on this board say the 1.7 is sharper at 1.8, but the only objective test I've seen found otherwise. Nifty 50 Shootout ERPhotoReview Maybe the people who preferred the 1.7 didn't use a hood, maybe they confused contrast with resolution, or quite possibly their copy was sharper. Most who say the 1.7 is sharper are just parroting someone else. In a test dgaies posted showing the two, most thought the 1.7 sharper and some (like me) found the opposite. One thing for sure, they are both great lenses, so you can't lose.

I fully agree with the last sentence.

However, I disagree with the rest. It's nickpicking, since indeed both lenses are great, but being an optical designer I know some stuff about contrast, sharpness, MTF, and all those other buzzwords we love On my K20D, my f1,4 was clearly less sharp AND less contrasty at f1,8 than my f1,7 wide open. Could it be anecdotal? Sure. But I think considering the sheer number of people observing the same thing, it's more than parrotting.

I still have sample shots even though I don't own the f1,4 anymore, I could show them to you if you'd like.

Here's a link to the sample shots (100% crops) of the FA50/1.4 and FA50/1.7. If I could do it over again (I don't have either lens at the moment), I would have taken more test shots under different conditions to try and answer the question more completely. However, at the time I was just trying to figure out which lens I wanted to keep (like the OP ).

The botton line is they are both fantastic lenses, and as many people have said, you really can't go wrong with either. My personal opinion (not just based on this particular test, but on real world shots too), is that the 50/1.7 is slightly sharper than the 50/1.4 at larger apertures. However, there are other factors (bokeh, color, the extra half-stop of speed, cost) that would be important to consider when choosing between the two lenses.

[mysticcowboy]

I've used both lenses and don't find any appreciable difference in in IQ. The half stop speed increase in the 1.4 isn't that valuable as the lens is very soft at that f-stop. You'll get at least a third more from the FA lens. On the other hand the FA is better built and has a metal filter thread.

[mysticcowboy]

I've used both lenses and don't find any appreciable difference in in IQ. The half stop speed increase in the 1.4 isn't that valuable as the lens is very soft at that f-stop. You'll get at least a third more from the FA lens. On the other hand the FA is better built and has a metal filter thread. I kept the F.

[bdery]

The botton line is they are both fantastic lenses, and as many people have said, you really can't go wrong with either. My personal opinion (not just based on this particular test, but on real world shots too), is that the 50/1.7 is slightly sharper than the 50/1.4 at larger apertures. However, there are other factors (bokeh, color, the extra half-stop of speed, cost) that would be important to consider when choosing between the two lenses.

My opinion exactly.

[Ratmagiclady]

Oh, why didn't I realize, you have your copies of both lenses in hand. Yes, a test!

I'd also suggest adding a test of people shots or any other favored subjects at those wider apertures, and see which you may like better subjectively.

[Flickeroo]

Oh, why didn't I realize, you have your copies of both lenses in hand. Yes, a test!

I'd also suggest adding a test of people shots or any other favored subjects at those wider apertures, and see which you may like better subjectively.

I had just a few minutes to set up a test, but I didn't choose my subject properly and the timing was wrong. The lighting wasn't constant (cloudy with sunny breaks) and it was quite windy. So a flower bush with trees in the background wasn't a good idea.

With what I did get it's really hard to tell them apart. But I need to set up something in my living room with constant lighting and no wind!

[audiobomber]

I need to set up something in my living room with constant lighting and no wind!

I suggest you do the test in daylight, since your K-x AF will misfocus at wide apertures under tungsten light. I usually shoot a cereal box indoors or outside in full shade, from about 6-8 feet. I like cereal boxes because they're colourful, they have printing that shows resolution very well (100% crop), they don't move in a breeze and they're small enough in the frame that you can get a good look at bokeh. Definitely use a tripod or solid stand and 2s timer.