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01-22-2013, 12:26 AM   #1
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Fa lenses on my k5?

What are the consequences or changes of putting an FA on an apsc lens? I see pentax makes majority of lenses as apsc. Why not make everything full frame so they work on both ff and apsc?

01-22-2013, 12:55 AM   #2
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QuoteOriginally posted by Scootatheschool1990 Quote
Why not make everything full frame so they work on both ff and apsc?

Lenses can be made smaller and lighter
if they only have to cover the APS-C frame.
And if a lens is lighter, the AF works faster.

As a comparison, the DA 15/4 Ltd
is a lot smaller and lighter than the A 15/3.5,
even allowing for the latter's built-in filters.
01-22-2013, 12:58 AM   #3
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QuoteOriginally posted by Scootatheschool1990 Quote
What are the consequences or changes of putting an FA on an apsc [camera]?
They'll work just fine.

You're cropping out a narrower field of view
from the central part of the FA lens's image circle.
01-22-2013, 01:04 AM   #4
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QuoteOriginally posted by Scootatheschool1990 Quote
What are the consequences or changes of putting an FA on an apsc lens? I see pentax makes majority of lenses as apsc. Why not make everything full frame so they work on both ff and apsc?
Consequence is that you don't get the same field of view that then lens is designed to produce. This has implications relating to larger Depth of Field for the same shot among other things. But the reason they don't make full frame lenses is due to the lenses costing more as there need to be more glass in the lens. Typically an increase in size and weight comes with the increase in the size of glass elements inside.

Pentax has not FF sensor in production so it doesn't make sense to make people pay for what they don't need.

01-22-2013, 01:39 AM   #5
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Ohhh okay. So then my next question : is my 14mm2.8 really a 21 in 35mm format? I know it won't work on an ff camera.
01-22-2013, 01:40 AM   #6
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Great photos. The FA lenses are great lenses and often cheaper second hand.
01-22-2013, 02:30 AM   #7
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QuoteOriginally posted by Scootatheschool1990 Quote
Ohhh okay. So then my next question : is my 14mm2.8 really a 21 in 35mm format? I know it won't work on an ff camera.
Yes, it has an equivalent FOV to 21mm on a FF camera.

FWIW, I use FA lenses more than any other series (on my K-5 and K-5 IIs).
01-22-2013, 02:31 AM   #8
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QuoteOriginally posted by Scootatheschool1990 Quote
Ohhh okay. So then my next question : is my 14mm2.8 really a 21 in 35mm format? I know it won't work on an ff camera.
FA lenses are full frame lenses. Its the DA's that are APSC. Your FA 14mm f/2.8 was designed for a film camera back in 'The Day' and as such would work on a FF Pentax digital camera should such a critter actually exist.

01-22-2013, 07:02 AM   #9
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QuoteOriginally posted by Scootatheschool1990 Quote
Ohhh okay. So then my next question : is my 14mm2.8 really a 21 in 35mm format? I know it won't work on an ff camera.
No a 14mm lens is a 14mm lens. To get the same field of view on a FF you would use a 21mm. To get the same field of view on M4/3 you would have to use a 10mm lens.
01-22-2013, 11:04 AM   #10
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QuoteOriginally posted by Sagitta Quote
FA lenses are full frame lenses. Its the DA's that are APSC. Your FA 14mm f/2.8 was designed for a film camera back in 'The Day' and as such would work on a FF Pentax digital camera should such a critter actually exist.
I think OP is referring here to the DA 14/2.8,
which was designed for APS-C format
(and which apparently now has the dubious distinction
of being the first DA lens to be discontinued.)
01-22-2013, 11:09 AM   #11
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QuoteOriginally posted by lytrytyr Quote
I think OP is referring here to the DA 14/2.8,
which was designed for APS-C format
(and which apparently now has the dubious distinction
of being the first DA lens to be discontinued.)
The OP has to be referring to the DA 14, it is the only 14mm lens Pentax has produced.
01-22-2013, 11:30 AM   #12
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QuoteOriginally posted by boriscleto Quote
The OP has to be referring to the DA 14, it is the only 14mm lens Pentax has produced.
Exactly.
01-22-2013, 04:18 PM   #13
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QuoteOriginally posted by lytrytyr Quote
Exactly.
Oh, durrr on me. The OP threw me in asking about FA lenses and I didn't bother doublechecking whether there was an FA version or not of the 14mm.

The fact I've been pricing the Samyang 14mm's today (which ARE ff) also messed with my head.
01-22-2013, 05:16 PM   #14
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QuoteOriginally posted by Scootatheschool1990 Quote
14mm2.8 really a 21 in 35mm format
No...your 14mm is a 14mm regardless. What happens in 35mm format is that the FOV is 1.5x wider then with APS-C. I would caution that that extra FOV needs to be matched by a bigger image circle or you will git huge shadows in the corners.


Steve
01-23-2013, 04:15 AM   #15
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QuoteOriginally posted by Sagitta Quote
The fact I've been pricing the Samyang 14mm's today (which ARE ff) also messed with my head.
If you get one, please show us what you do with it.

I use wide angles for architecture (among other things),
so the 5% barrel distortion would bother me,
and correcting it would kill some of the lens's great edge resolution.
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