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05-23-2010, 03:23 AM   #16
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QuoteOriginally posted by krandle Quote
It never ceases to amaze me how condescending some "pentaxians" can be to people simply trying to learn. Thank Zeus that the vast majority of experienced photogs on this forum know that it is here to educate and inform anyone and everyone regardless their level of experience. Snobbery alienates.

Had to say something!
It's true how amazing it is that 1.5x can bring up so many problems/questions.

And it also never ceases to amaze me how people on here massively over react to stuff and are generally over sensitive to everything.

05-23-2010, 04:41 AM   #17
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But it is a widely misunderstood concept. There was someone who wrote a long review of the kx who didn't understand that the FA 43 had a focal length that was covered by the kit lens (18-55). I think it all goes back to the camera companies selling APS-C cameras as though they added length to lenses, when all they really do is crop the center portion of the lens.

To the OP: you just have to take our word for it, the thing that changes with APS-C is not the lens length, it is the sensor. The field of view will change from a film sensor to an APS-C sensor, but not because the lens has changed, but just because less of the image circle is captured with APS-C.
05-23-2010, 06:53 AM   #18
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I've done this simple experiment: put the DA lenses on a my MZ5n body... and I've seen...
It's true how amazing it is that 1.5x can bring up so many problems/questions
This probably because the concept is not well understood or well explained. Part of the problem is in the fact that camera companies are not so transparent, the K7 manual is not very clear for a 35mm experienced guy but APS beginner...

Look at how many people explained the same concept in so many different ways...

I'm considering to take a degree in light physics
anyway now I hope that is clear for me...

thanks all again !
05-23-2010, 07:37 AM   #19
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You're over thinking it .... really it's not as complex as people make it sound. Just x1.5 ... that's it, end of story .... x1.5.

05-23-2010, 08:07 AM   #20
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When light passes through the lens, when not attached to any camera, will produce a circle of light behind it.

Now take this lens and attach it to a film camera. Same circle of light behind it. The larger "sensor" of film behind it is inside the circle of light.

Now attach this lens to a dSLR. The sensor is smaller, but the lens is still casting the same circle of light.

The result is that the dSLR has the exact same image from the lens to work with, but since its sensor is smaller, it can't capture the as much of it. The image is the same as the film image, but cropped by 1.5x.

So, the focal length is still the focal length, the lens doesn't change depending on what camera it is mounted to. Its the camera sensor size that is changing. This doesn't effect the lens' focal length.
05-23-2010, 01:07 PM   #21

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I said this long ago.

Focal length is focal length is focal length, without regard to sensor size. Period.

As an example, as stated somewhere here before. if you have a lens that projects a focused image of, say a square, that is 10mm on each side. That lens will project the same sized image on any given sensor of any given size.

On a APS-C sensor - 10 mm square.
On a 135 format (so called full frame) - 10 mm square.
On a 645 format - 10 mm square.
On a 4x5 sheet of film - 10 mm square.

The focal length never changes, the size of the object on the sensor never changes. What changes is the size of the sensor, not the size of the objects.

Crop factor is a way of comparing sensor sizes, not focal length.

The Elitist - formerly known as PDL

Last edited by PDL; 05-23-2010 at 01:10 PM. Reason: spacing

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