[dgaies]

Because he was asking primarily because he wants autofocus.

Autofocus isn't a great reason to invest in an FA limited IMHO. There are other reasons that are good, but not a desire for autofocus.

I mean, the F 50 1.7 is only 200 bucks.

True, the OP stated that he wanted AF and that he was interested specifically in the FA43 and how it compared to his M50/1.7 (aside from having AF). Certainly nothing wrong bring up other options such as the F50/1.7, DA35/2.4, DA40, etc.; they're all great lenses that would serve the OP well and at a lower cost than the FA43. However, I still fail to see how the price of his existing lens (the M50/1.7) has anything to do with whether or not he "needs" the FA43. The purchase of whatever lens he decided to buy should be made based on the attributes of the new lens, which would certainly include cost and value.

[rparmar]

I DO see a difference in sharpness (the FA 77 is VERY sharp, even from wide open). I believe this sharpness gives the lens a *pop*, which is what makes it so coveted.

It is not the sharpness that does this, but the specific choices made in the optical design process as mentioned earlier. Otherwise all sharp lenses would have the same look, but plainly they don't.

If sharpness is your only criteria though, the 50 1.7 is no joke either. It's a great lens for about 1/9th the price.

Sharpness is not my only criteria or many lenses could do the job.

I don't care about image tests, or resolution charts. I compare real images with my eyes to make decisions.

A proper MTF plot (with S and M curves for both contrast and resolution) reveals loads of info about a lens that would otherwise take thousands of shots to determine. Not caring about relevant data is an odd attitude for someone who wants to argue lens versus lens. It is much easier for your eyes to be fooled by composition and other extraneous factors. And almost impossible outside a lab situation to take two identical photos to make a comparison meaningful.

I would rather read the MTF charts and then spend my photographic time taking images I want to take, and not making my own (inferior) test shots. (Though I have been known to do that as well to satisfy my own curiosity.)

[paperbag846]

I currently have a Pentax 50mm 1.7 and I love it for it's low light performance, bokeh, build quality and size-- these are all things that I value. However, I don't have the greatest eyesight which makes focusing difficult, and I think I would greatly appreciate an AF around this focal length.

Getting away from this extremely tangential subject, your options are:

1) FA 43 ~570 dollars (the best overall, but not flawless. autofocus may hunt in low light, sometimes busy bokeh like the 1.7. this is the sharpest lens).
2) DA 40 ~360 dollars (also amazing, but only f2.8. fastest autofocus).
3) FA 50 ~ 360 dollars (best bokeh, cheaper-feeling design makes no difference in practice, autofocus can hunt in low light like the FA 43. corner sharpness is not as good as the limiteds).
4) F 50 1.7 ~200 dollars (exactly what you have, but autofocus. worth looking into - this is a great lens as you know).

[paperbag846]

It is not the sharpness that does this, but the specific choices made in the optical design process as mentioned earlier. Otherwise all sharp lenses would have the same look, but plainly they don't.

Because most lenses aren't sharp from 1.8. I'm not going to buy your argument until you get specific. The only things that make the 77 special are (1) sharpness wide open, (2) strong coloured aberrations in high-contrast areas of a scene -- not really a plus, (3) buttery bokeh -- common to many lenses in the 85mm range (however... not all of them are sharp at f1.8..)

For the layperson it's not helpful to discuss "optical qualities" like they are some magical decision, or to treat lenses as "black boxes". Break it down. A lens gives you colour, contrast, bokeh, and dof. The *major* differences between the DA 40 and FA 50 are different colours, higher contrast for the DA, less DOF for the DA. There might be some other subtle differences, but most people don't care about them, and I think that this general approach gives most people *enough* of an idea to tell whether they would be happy with a lens.

My experience with the LTDs have taught me something - there is no free lunch, you ALWAYS are making compromises with lenses. There is no lens that is small, fast, and optically perfect. The FA 77 has harsh chromatic abberations, the DA 70 is slow. The FA 50 is not nearly as sharp as the 43, but it has creamier bokeh. One cannot simply look at the price tag and deduce that "this is the best lens, because it is most expensive". Even with the most expensive glass, you are making some compromises.

Here is an important point: A compromise that a pro would find acceptable (largely because he/she can compensate with skill) might *not* be acceptable to a layperson.

[rparmar]

For the layperson it's not helpful to discuss "optical qualities" like they are some magical decision, or to treat lenses as "black boxes".

I am not discussing them as though they were magic -- quite the opposite. I am saying that different decisions were made for the FA Limiteds than have been made for other lens lines. Practical design decisions.

You don't need to believe me but you do need to believe the lens designer Jun Hirakawa. Read his documents.

We only call it "magic" because it's simpler than saying: "Rather than perfectly correcting for field curvature, the FA Limited lenses completely correct astigmatic difference in both meridional and sagittal subject planes, allowing small amounts of field curvature to remain."

[rparmar]

One cannot simply look at the price tag and deduce that "this is the best lens, because it is most expensive". Even with the most expensive glass, you are making some compromises.

I said nothing of the kind. I can see now that you are not interested in actually reading what I am saying, checking references or doing your own research. It's a lot easier to simply question my motives.

I will now leave this thread.

[paperbag846]

I said nothing of the kind. I can see now that you are not interested in actually reading what I am saying, checking references or doing your own research. It's a lot easier to simply question my motives.

I read every word and gave it some thought. I think the difference here, is that I am trying to address OP's question, and you want to discuss *very* technical stuff (or glaze over it with catchphrases like "optical design decisions"). When I was a beginner, I thought I had a lot to learn with people here comparing charts. Then I realized most skilled photographers don't give a rat's *** about technical qualities and compare what the eye can see.

Wander over to a audiophile forums, and then go talk to musicians. You will see the same pattern of behaviour.

Besides, the OP asked "what differences will I notice between the 50 1.7 and the 43 1.9?"

Your first answer was "It is not the sharpness that does this, but the specific choices made in the optical design process as mentioned earlier." Pretty vague. You second attempt was a muddled pile of jargon that no one should really care about (unless you an optician).

Dumb it down for the OP and the general population. It's much more helpful. The fact is that for most people, you need to look at pictures to see the difference between these lenses (to *really* understand them).

We should set up a comparison thread, to sticky. Not test shots, real world pictures, that flaunt the best of each lens. That would help a lot of people decide what they actually "need" to get the photos they "want".