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06-13-2016, 06:09 PM   #1
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FF and APS-C Specs

I just would like to confirm these specs. The Pentax 24-70 would cover the 24-70 range on the K-1, and the 37-107 range on the K-3II. The Pentax 70-200 would cover the 70-200 range on the K-1, and the 107-307 range on the K-3II.

I have a 16-85 aps-c lens on my K-3II right now, and if the lenses I mention above covered something other than that range on the K-3II in aps-c it may be interesting to know. Of course if I had either of them, I would most likely make use of it on a K-1.

Thanks ahead for any input.

06-13-2016, 06:36 PM   #2
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the 16-85 is based on FF measurement. so on the K3ii, you're actually seeing 24-130ish. if you put 16-85 on the K1 then you'll see 16-85.
when they said it a aps-c lens, it means the element is special made for aps-c sensor, so if you put it on a FF camera, it will not cover the whole sensor which leads to vignetting
06-13-2016, 06:40 PM   #3
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The crop factor on a K-3 II is 1.5. So a 24-70 is '35mm equivalent' to a 36-105. The 70-200 is 105-300. That of course only applies to FoV.

The 16-85 Is a 24-128 'equivalent'.
06-13-2016, 06:46 PM   #4
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Thank you to you both. That is what I needed to know.

06-13-2016, 07:28 PM - 1 Like   #5
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QuoteOriginally posted by C_Jones Quote
I just would like to confirm these specs. The Pentax 24-70 would cover the 24-70 range on the K-1, and the 37-107 range on the K-3II. The Pentax 70-200 would cover the 70-200 range on the K-1, and the 107-307 range on the K-3II.

I have a 16-85 aps-c lens on my K-3II right now, and if the lenses I mention above covered something other than that range on the K-3II in aps-c it may be interesting to know. Of course if I had either of them, I would most likely make use of it on a K-1.

Thanks ahead for any input.
The 24-70mm covers 24-70mm on both cameras, same for the 70-200mm. Focal length is focal length.

The field of view of the 24-70mm mounted on the K-1 would correspond to that of a 16-50mm lens on the K-3; the field of view of the 70-200mm mounted on the K-1 would correspond roughly to the field of view of the DA* 50-135mm on the K-3.

If you were to set the 24-70mm to 50mm and the 16-50mm to 50mm and mount them on your K-3, you'd get the same image.

When using the 24-70mm on the K-3, you can directly compare the focal length to the 16-85mm; i.e. the latter is both wider at 16mm at longer at 85mm.

Hope this clears things up!

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06-13-2016, 08:04 PM   #6
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That is really clearly stated and answers my question.

Thank you Adam.
06-13-2016, 09:57 PM   #7
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I think this highlights a reality that the traditional "35mm" equivalent is in reality become an "apc" equivalent. I for one have a better feel of a lens on a crop camera, so I always factor back to my crop camera FOV than the other way. In my mind the 15-30 on the K1 is "equivalent" to my 10-20 on my K5 - I know what a 10-20 looks like!

(Confession time.. Waiting for the backlash from the purists....)

06-13-2016, 10:40 PM   #8
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QuoteOriginally posted by Timd Quote
Waiting for the backlash from the purists....
No backlash, unless you have extensive 35mm film experience you are far more used to the APS-C field of view than the FF field of view. I think a lot of folks, myself included, are having the same issue transisting to the K-1. While the old film hands are happy their lenses now look "the way they are supposed to", those of us from the digital era are having to adjust.

I can say that I've successfully moved to the K-1 and it was not nearly as hard to adjust as I thought it would be.
06-14-2016, 09:53 AM   #9
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Isn't all focal lengths are per 35mm (FF) spec regardless of DA or FA? The ones made for APS-C just happen to have a smaller image circle since the FOV is smaller for APS-C and gives us a virtually zoomed in feel due to the crop.
06-14-2016, 10:33 AM   #10
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As Adam wrote above, focal length is physical property of the lens itself, independent of any camera it could be mounted on. The combination of the lens focal length and the camera sensor size determine the field of view.
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