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07-26-2013, 10:22 AM   #1
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Welcome to everybody !!

Hello to everybody,

I recently both a K30 Pentax and I am starting to take good pictures in a course. I algo got from my father a package of 6 good SMC FA lenses he had from his old 35 mm Pentax camera.

I will be uploading my pictures once in a while.

By the way, can somebody tell me how to calculate the conversion of the focal lenghts of the FA lens to the digital area ? For example, what is the 28 mm FA lens corresponding to a DA lens ?

Sincerely,

Jorgario

07-26-2013, 10:39 AM - 1 Like   #2
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QuoteOriginally posted by Jorgario Quote
Hello to everybody,

I recently both a K30 Pentax and I am starting to take good pictures in a course. I algo got from my father a package of 6 good SMC FA lenses he had from his old 35 mm Pentax camera.

I will be uploading my pictures once in a while.

By the way, can somebody tell me how to calculate the conversion of the focal lenghts of the FA lens to the digital area ? For example, what is the 28 mm FA lens corresponding to a DA lens ?

Sincerely,

Jorgario
The crop factor is 1.5x, which means that your lenses will not be as wide on digital as they were on film. So, a 50mm on digital will feel like a 75mm on film, and vice-versa. The focal length does not change, ever, though.

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07-26-2013, 10:42 AM   #3
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QuoteOriginally posted by Jorgario Quote
I algo got from my father a package of 6 good SMC FA lenses he had from his old 35 mm Pentax camera.
Lucky you! Welcome to the forum

QuoteOriginally posted by Jorgario Quote
By the way, can somebody tell me how to calculate the conversion of the focal lenghts of the FA lens to the digital area ? For example, what is the 28 mm FA lens corresponding to a DA lens ?
Jorgario, strictly speaking the focal length of the lens does not change. You can speak of "effective focal length" instead which tells you the focal length of a lens that will have the same angle of view on a 35mm camera as the lens in question on the cropped sensor. The APS-C sensors that Pentax uses are 1.5 smaller than 35mm film (in linear dimensions). This is called "crop factor". Effective focal length = Crop factor x the actual focal length of the lens.

So a 28mm lens mounted on your K-30 will have the same angle of view as a 28x1.5 = 42mm lens mounted on a 35mm camera. I.e. your 28mm lens can be considered to be a "normal" lens on the K-30

Same applies to any DA lens. The focal length given for all DA lenses is their actual focal length, not their effective focal length. I.e. the DA40 would have the same focal length as an FA40. For example the DA 15 Limited has the same angle of view as 15x1.5 = 22.5mm lens mounted on a 35mm camera

Last edited by vanyagor; 07-26-2013 at 10:47 AM.
07-26-2013, 10:57 AM   #4
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Welcome to PF and bonjour from France ... hope to see an image or two soon ... J

07-27-2013, 11:47 AM   #5
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QuoteOriginally posted by Jorgario Quote
tell me how to calculate the conversion of the focal lengths
Everyone's beaten me to the post with answers, so I'll just say welcome to the forum and enjoy it.
07-27-2013, 08:24 PM   #6
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QuoteOriginally posted by vanyagor Quote
Lucky you! Welcome to the forum



Jorgario, strictly speaking the focal length of the lens does not change. You can speak of "effective focal length" instead which tells you the focal length of a lens that will have the same angle of view on a 35mm camera as the lens in question on the cropped sensor. The APS-C sensors that Pentax uses are 1.5 smaller than 35mm film (in linear dimensions). This is called "crop factor". Effective focal length = Crop factor x the actual focal length of the lens.

So a 28mm lens mounted on your K-30 will have the same angle of view as a 28x1.5 = 42mm lens mounted on a 35mm camera. I.e. your 28mm lens can be considered to be a "normal" lens on the K-30

Same applies to any DA lens. The focal length given for all DA lenses is their actual focal length, not their effective focal length. I.e. the DA40 would have the same focal length as an FA40. For example the DA 15 Limited has the same angle of view as 15x1.5 = 22.5mm lens mounted on a 35mm camera
Thanks for the explanaciones and the cross factor !!
07-27-2013, 08:25 PM   #7
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QuoteOriginally posted by kerrowdown Quote
Everyone's beaten me to the post with answers, so I'll just say welcome to the forum and enjoy it.
Thanks !!
07-27-2013, 08:28 PM   #8
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QuoteOriginally posted by Jean Poitiers Quote
Welcome to PF and bonjour from France ... hope to see an image or two soon ... J
Merci bien !!

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