What is the difference between f2.0 and f1.7 50mm pentax lens?

I am new to photography and was given a pentax a3000 and want to buy

a normal manual lens of 50mm. What is the difference day to day of

the different ones?

the glib answer would be f/0.3

 

Pentax's "standard" 50mm lens was the f/1.7 and they introduced an f/2.0 as a cost reduced option. At one point we had an f/1.7 on my Dad's ME, and an f/2.0 on my MG, and frankly I couldn't tell them appart. In theory the f/1.7 is better optically (and I think the faster lenses they did were better still) but in practice, pretty darn hard to tell.

Half a stop - brighter viewfinder, precise focusing if you want to focus on a ground glass.

 

Not sure about the difference in optical quality, but in many cases film is a bigger limiter factor than a 50mm prime.

Edmund,

 

As others have noted the f1.7 is a 'faster' lens than the f2.0. What that means is that if you set the lens at it's widest aperature (f1.7 or f2.0) and you have the same film in the exact same light that the f1.7 will open and close about a 'half shutter speed' faster than the f2.0. In principle that means that there is less chance for camera shake with the faster lens. In practice you are not likely to see much difference unless you are shooting in low light.

 

Another slight difference, at f1.7 you have a narrower area that is in focus (when shooting at the widest aperature). The nice thing is then that subject 'pop-out' of the background a little better. Again in practice at f1.7 vs f2.0 the difference is likely to be small.

 

The 50mm f1.7 A lens is said to be amungst Pentax's best lenses-but that difference will likely be hard to judge unless you are shooting under controlled conditions.

According to Boz' page the f1.7 should be a bit better optically. I liked my f2.0 a lot for the comparable better feeling of the aperture ring.

Cheers for the replies, I did not expect such a big response. I kinda knew the 1.7 was better but I did not know how and why so thanks for clearing that up for me. I ordered one there from jessops. Looking forward to it now. All the best

I have both. About 1/3 stop difference is no real diffeence at all with todays superior and faster films. They say the 1.7 is slightly better. Either way, they are both inexpensive enough to obtain.

 

On quality: even after 40-some years of photography, I have yet to be able to blame a bad photo on the lens.

Your being new to photography, I'll say this if you choose to be serious about our passion. Most likely if you start with an f2 you will be wanting a f1.7. Then later you probably will have the urge to get a f1.4. And so it goes. Jim

As many have allready said,the f1.7 is ever so slightly better optically.It's tricky to see much difference because they are both VERY sharp.The f1.7 is better built if my memeory serves me correctly.I've serviced several of both of them (some time ago now)and *think* i recall that the f2 is very cheaply built.

<br>End result-either of them will do very well but try to get the 1.7

I have the f2 and love it. Now I want a f1.7! DANG IT!

I bought a 2.0 for my wife, a beauty, and so is the lens. Very compact and razor sharp.

My favorite Pentax 50mm is the 1.4. You can get almost religious arguments over which is

better, the 1.4 or the 1.7... The 2.0 is a great deal for the money and is remarkably flare

resistant. I have a shot on my website (red leaves) that shows off that quality quite well.

The 50mm f2 was my favorite cheap lens...

 

Isaac

 

www.homepage.mac.com/isaacc7

Ed, I've had 4 different Pentax K-mount 50 f2's, all were,in my view, were plenty good enough for anyone. Oh yes, the difference: one element and 1/2 stop...Jim...P.S. all of the world's greatest photographs for photography's first hundred years were taken with lenses with less than 5 elements.