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03-15-2008, 07:49 AM   #1
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Difference between pentax FA and F

I want to buy a f1.7 50mm for my K10d and I have found on sale both
the smc F and the FA.

Could anybody explain to me in what the FA lenses differ from the F ones?

I have tried a search in the forum but I could not find any info, hope I am not posting something that has been answered already.
I have found a f1.7 50mm F for £99 on amazon uk, which is £50 less than the average price for a 1.7 FA. (the seller advertised it as an FA 1.4 and has no feedback , so I might not take it, but it would be good to know the difference between FA and F for the future)

By the way this is a really nice forum, the lenses reviews are absolutely great!

Thanks!

Aldo

03-15-2008, 08:22 AM   #2
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Wikipedia provides some information about the F and the AF:

Pentax K-F mount - Wikipedia, the free encyclopedia

Pentax K-AF mount - Wikipedia, the free encyclopedia

I am not exactly sure what it means, sorry.
03-15-2008, 08:30 AM   #3
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Thanks!
I ll have a look right now.
03-15-2008, 09:27 AM   #4
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Uuups, With a bit of extra 'googling' I have found the information.
I ll post it here in case somebody is intererested.

So, in brief, in some cases the fa lenses are a re-package of the equivalent
pentax f lenses, with the difference that the FA have a chip that transmits exposure values and other information to the camera.
This means that using an F lense on a digital camera, the metadata embedded in the photo will lack some information.
An example is the focal lenght used, which is obviously irrelevant with a prime, but will require K10 users to set manually the focal lenght on camera for the image stabilizer to work properly.
As for the build and image quality, it seems there are not relevant differences (so good image quality and noisy autofocus).
___________

In brief:
>The FA lenses, as a group, have a chip that sends MTF
> >data to the camera body (so that the MTF program
> >exposure will work), and send focus distance to the
> >body (used for metering and flash). The F lenses do
> >not send MTF information, and I don't think they send
> >focus distance either.

From RE: Difference between F and FA lens?

Also : VanNatta: Pentax F auto focus Lenses

03-15-2008, 09:32 AM   #5
Ole
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QuoteOriginally posted by McAldo Quote
I want to buy a f1.7 50mm for my K10d and I have found on sale both
the smc F and the FA.

Could anybody explain to me in what the FA lenses differ from the F ones?


Aldo
The lenses are optically identical. The cosmetic design is different; the focusing ring of the FA is a tad wider. Next, the FA lens transmits MTF information to the camera, which lets the camera select the sharpest aperture when set to the "MTF" program. The MTF program is close to useless, however, since it is more important to set the aperture to achive the desired depth of field, or to accomodate the desired shutter speed.

It thus basically comes down to cosmetics. If you plan on using manual focus you may want to pay the extra $$$ for the wider aperture ring.
03-15-2008, 09:35 AM   #6
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Not entirely correct

QuoteOriginally posted by McAldo Quote
Uuups, With a bit of extra 'googling' I have found the information.
I ll post it here in case somebody is intererested.

So, in brief, in some cases the fa lenses are a re-package of the equivalent
pentax f lenses, with the difference that the FA have a chip that transmits exposure values and other information to the camera.
This means that using an F lense on a digital camera, the metadata embedded in the photo will lack some information.
An example is the focal lenght used, which is obviously irrelevant with a prime, but will require K10 users to set manually the focal lenght on camera for the image stabilizer to work properly.
As for the build and image quality, it seems there are not relevant differences (so good image quality and noisy autofocus).
___________

In brief:
>The FA lenses, as a group, have a chip that sends MTF
> >data to the camera body (so that the MTF program
> >exposure will work), and send focus distance to the
> >body (used for metering and flash). The F lenses do
> >not send MTF information, and I don't think they send
> >focus distance either.

From RE: Difference between F and FA lens?

Also : VanNatta: Pentax F auto focus Lenses
F lenses do transmit focal length. The only information missing is the close-to-useless MTF data.

I have F and FA lenses, and they work the same on the K10D in every aspect except the MTF program.
03-15-2008, 10:24 AM   #7
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QuoteOriginally posted by KjetilH Quote
Wikipedia provides some information about the F and the AF:

Pentax K-F mount - Wikipedia, the free encyclopedia

Pentax K-AF mount - Wikipedia, the free encyclopedia

I am not exactly sure what it means, sorry.
These are descriptions of two iterations of the Pentax K lens mount, not of the F- and FA-series lenses.
03-15-2008, 10:25 AM   #8
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As Ole says, the F lenses do transmit the info to exif. I have an old Takumar F 28-80 that I used at the Supermoto races last May, and just took a look at them, and all of the info is there.

03-15-2008, 03:27 PM   #9
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QuoteOriginally posted by Ole Quote
Next, the FA lens transmits MTF information to the camera, which lets the camera select the sharpest aperture when set to the "MTF" program. The MTF program is close to useless, however, since it is more important to set the aperture to achive the desired depth of field, or to accomodate the desired shutter speed.
My F*300 appears to transmit MTF data, my K10D auto sets an aperture f6.3 when shooting MTF line in P mode.
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