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03-26-2012, 10:24 AM   #1
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FF lens vs APS-C lens

both at 35mm.... is there a diff between a lens made for FF and a lens made for APS-C? would the result be the same? i feel compelled to buy FA's instead of DA's just in case i end up with a FF Pentax body... but right now... is there a significant reason to buy an FA 35mm rather than a DA 35mm?
still confused after reading a lot of texts, help.

03-26-2012, 10:40 AM   #2
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Take a look at the similar threads at the bottom of this page- this topic has been discussed a lot already and there are plenty of answers sprinkled throughout various threads. In a nutshell, an FF lens will perform better in terms of vignetting as you're only using the center of the frame, but it may have a lower resolution or worse flare resistance than a lens optimized for digital (this especially applies to older manual lenses).

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03-26-2012, 10:52 AM   #3
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the fundamental differences between a DA35 and FA 35 will be as follows:

- the coatings on the DA will be better because they are newer, and things like coatings are always advancing
- the FA lens may be a little heavier because the use of plastics has been increasing, and because some internal parts such as the rear element may be bigger to cover the larger frame
- the rear element on the DA will be specially coated to reduce reflections from the sensor, that lead to lost contrast, the FA will not have this coating unless it is a DFA lens
- the FA lens may, when used on a digital camera, have lower contrast because it will be allowing light to cover a full 24 x 36 mm frame into the mirror box and shutter area. although the interior is black, it may still lead to some increased light being scattered al around and lower contrast on the sensor,
03-26-2012, 11:10 AM   #4
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I prefer the F and FA as they have an aperture ring.
Jake

03-26-2012, 12:14 PM   #5
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Besides all the good info above, here are some other points about FF vs DA / APS-C lenses:

* If you ever expect or intend to use a FF film or digital SLR, APS-C lenses won't be appropriate.
* APS-C lenses can be wider|shorter than FF lenses -- ultrawide FF glass is quite rare and costly.
* FF lenses with lesser edge performance have their weakest areas cropped by APS-C sensors.
* New APS-C lenses will be under manufacturer's warranty; old FF lenses are all caveat emptor.
-- EDIT: Forget this last one if you're buying only new FA lenses.

Other than what's already been mentioned, it's hard to generalize across the vast range of available lenses; they must be judged individually. Some FF lens types just aren't made in APS-C versions: the ultrafast, like the 50/1.2s, and slower primes, like classic old f/4.5s. Many newer APS-C zooms perform considerably better (if more homogeneously) than their FF ancestors. Think of it as evolution in action.

Last edited by RioRico; 03-26-2012 at 10:43 PM.
03-26-2012, 12:29 PM   #6
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QuoteOriginally posted by Lowell Goudge Quote
- the coatings on the DA will be better because they are newer, and things like coatings are always advancing - the FA lens may be a little heavier because the use of plastics has been increasing, and because some internal parts such as the rear element may be bigger to cover the larger frame - the rear element on the DA will be specially coated to reduce reflections from the sensor, that lead to lost contrast, the FA will not have this coating unless it is a DFA lens - the FA lens may, when used on a digital camera, have lower contrast because it will be allowing light to cover a full 24 x 36 mm frame into the mirror box and shutter area. although the interior is black, it may still lead to some increased light being scattered al around and lower contrast on the sensor,
While all this may be true I would be skeptical if it would lead to anything clearly noticeable in the resulting images. The FA 35 is not that old of a lens (released in 1999); and the DA 35 supposedly has a full-frame image circle, so not sure about the reduced contrast due to larger image circle. The only time I've noticed reduced contrast in older lenses is when using zooms which feature a lot of lens elements. Both these 35mm lenses have six elements in five groups. If the coatings on the DA lens are slightly better, it shouldn't make much of a difference, at least not one that has any practical significance. What might be noticed is that the lens render color differently, as FA lenses in general have slightly different look from DA lens. Not necessarily better or worse, but different.
03-26-2012, 01:04 PM   #7
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With regards to the two 35's discussed I don't see much of a reason to get the FA35 at this point. The DA is almost half the price new with a warranty.

Sure there are a few that still shoot film and a few that want to use it reversed or on tubes but the vast majority of us would benefit more from saving the $150 dollars.

As far as a potential FF camera upgrade (if it ever exists), don't sweat it now. If you're considering this in the next two years (if it exists) then your budget now should include either the FA31/43 instead. If you plan on upgrading in more than two years then take that extra money and put it towards a FA50/1.4 (if you don't have one).

I can't remember if it was the DA35 or the DA40 (or both) but the optics are the same except the rear element is slightly smaller. Not sure if this means there would be any difference on FF they should perform similar on APSC.
03-26-2012, 01:29 PM   #8
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Are you by any chance asking about the behaviour of FF lenses on APS-C? As in, the FOV difference?

03-26-2012, 06:16 PM   #9
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Just coming from a common enthusiast,,, to invest in a system is a serious matter (money matters) pentax as good as it has been just frustrates it's loyal followers.. How about some reward for a change? the K7/K5/Kx/Krs were good... everybody just keeps on guessing the about the future... where it leads...
the "being left out" feeling is strong. i'm sure i am not alone about this issue.
it is an investment... just trying to be smart about it now... acessories etc... flash and most importantly lenses...
all replies helped a lot...

Last edited by tristan; 03-26-2012 at 06:17 PM. Reason: additional stuff
03-26-2012, 06:18 PM   #10
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and thank you guys...
03-26-2012, 09:12 PM   #11
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Everything else aside I don't own any APSC lenses for the same silly reason, just planning that far ahead and hoping for a full frame. I also don't own anything I can't use on my old film camera.

Something to consider is the full FA line will be updated (as in optimized for digital) and re-released should there ever be a FF digital body to go with it. So you could go with a few DA's and sell them with your APSC body later, especially the super wides which as mentioned are impossible to get in FF.
03-27-2012, 12:12 AM   #12
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QuoteOriginally posted by PPPPPP42 Quote
Everything else aside I don't own any APSC lenses for the same silly reason, just planning that far ahead and hoping for a full frame. I also don't own anything I can't use on my old film camera.

Something to consider is the full FA line will be updated (as in optimized for digital) and re-released should there ever be a FF digital body to go with it. So you could go with a few DA's and sell them with your APSC body later, especially the super wides which as mentioned are impossible to get in FF.
but the DA35 used the FA35 optics. Is there anything that suggests it won't work on digital other than the DA designation that Pentax gave it?
03-27-2012, 12:21 AM   #13
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QuoteOriginally posted by Lowell Goudge Quote
- the FA lens may, when used on a digital camera, have lower contrast because it will be allowing light to cover a full 24 x 36 mm frame into the mirror box and shutter area. although the interior is black, it may still lead to some increased light being scattered al around and lower contrast on the sensor,
Strange then that nobody saw an oppertunity for aftermarket rear lens element shims, to shade out the excess light when used on APSC.
03-27-2012, 06:19 AM   #14
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@giklab... yup... i experimented with it... 50 mm 1.7M and the 18-55 kit... just want to make sure i see all the right (or wrong) reasons to invest on DA's and the/or any aps-c lenses out there. they are cheaper(at least most of them) not necessarily cheaply built,,, esp not in the limited DA. sure love those old lenses,,, but is it still taboo for serious photographers to use autofoucus?
03-27-2012, 06:30 AM   #15
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QuoteOriginally posted by Clavius Quote
Strange then that nobody saw an oppertunity for aftermarket rear lens element shims, to shade out the excess light when used on APSC.
you will note in my comment i state MAY not DOES.

I do not know how much impact the stray light inside the mirror box bothers things, it is a theoretical possibility. The same is true about rear element coatings on digital lenses, often touted as a necessity, but in my collection of 45 lenses (where only 6 are digital era designed lenses) i have not had a lot of issues with either.

BTW, of my 45 lenses only 3 are designed for ASP-C, all the rest are full frame lenses, and I do still use them on my film bodies (principally my PZ-1) from time to time
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