[RobG]

Hi Rob; So stupid question, but what did he say about using the D-FA150-450 on the K3III. Does it work ok. Will all Full Frame lenses be compatable? Thats all I have now

Oh! Sure, it works fine, just like the lens works fine on my K3. I see no reason why any full-frame lens would be incompatible, other than to say that due to the crop you won't get the same effective focal length. However, because of the crop, I have the impression that I get better sharpness from the DFA 150-450 than with a K1, but that's just an impression since I don't actually own a K1 to compare it. I'll try to figure out what he says at that point about the DFA 150-450 more accurately, but I think he was simply saying that the focal length is different because of the APSC sensor. Some of the earlier photos at Shiretoko used the DA560 rather than the DFA 150-450.

[Kunzite]

Oh! Sure, it works fine, just like the lens works fine on my K3. I see no reason why any full-frame lens would be incompatible, other than to say that due to the crop you won't get the same effective focal length. However, because of the crop, I have the impression that I get better sharpness from the DFA 150-450 than with a K1, but that's just an impression since I don't actually own a K1 to compare it. I'll try to figure out what he says at that point about the DFA 150-450 more accurately, but I think he was simply saying that the focal length is different because of the APSC sensor. Some of the earlier photos at Shiretoko used the DA560 rather than the DFA 150-450.

Sigh... no, there is no "effective focal length", and the focal length is not different - it stays the same, regardless of the format and even without the lens being put on a camera.

I know the "effective focal length" is a widely used nonsense, Ricoh Imaging is using it as well, but people are getting convinced that a lens at 300mm has a different angle of view than a lens at 300mm, when put on the same camera. We had such cases.

Let's keep simple things simple, and in this case also accurate:
- there's no change in the focal length by putting the D FA 150-450 on either a FF or an APS-C camera (or a medium format if you can adapt it, or on an improvised shoebox camera).
- talking about crops and angle of view - the lens will behave no different from an APS-C lens on said APS-C camera. At 300mm it will show the same angle of view as an APS-C 300mm.

What is happening? The lens is covering the FF format, in other words it's projecting an image sufficiently large so you could get an useful 24x36mm out of it. Well, the only change is that you'd get a smaller, APS-C sized rectangle - because that's how big your sensor is.
If it was the other way around - using an APS-C lens on a FF camera - then you'd have to ask, can this lens, guaranteed to offer an useful APS-C-sized image, actually get me a larger usable image? Some DA lenses do that, even to the extent they have been designated as officially being FF (the DA*200mm, DA*300mm, DA 560mm). Some do that well enough that we're happy with the results. Some do that partially, or not at all - so we'd have to crop.

OTOH, Pentax has no restrictions about putting a K-mount FF lens on an APS-C camera or the other way around.

[bxf]

Sigh... no, there is no "effective focal length"

True, but there is "effective view of focal length"

[Pål Jensen]

It is the angle of view that's different. Focal length is focal length regardless of format You use different focal lengths on different formats to achieve the same angle of view....

[Kunzite]

True, but there is "effective view of focal length"

No, there isn't.
Although somewhere in Romania there's a road on which 1 km has 800m; I guess that was an "effective view of length". But unless there's some fraud involved, the length doesn't change.

[Kunzite]

It is the angle of view that's different. Focal length is focal length regardless of format You use different focal lengths on different formats to achieve the same angle of view....

Yes, this must be understood - it makes no sense to complicate your life if it's not about different formats.

[bxf]

No, there isn't.
Although somewhere in Romania there's a road on which 1 km has 800m; I guess that was an "effective view of length". But unless there's some fraud involved, the length doesn't change.

I think you may have over-complicated my comment. If I'm looking through a 50mm lens but I'm seeing what a 75mm lens would show (on FF), then I'm getting "effective view of 75mm". I'm not sure I can see any other way to interpret such an example.

[Serkevan]

We are getting dangerously close to invoking the Big E Word here, everyone tread carefully! :P

[RobG]

Sigh... no, there is no "effective focal length", and the focal length is not different - it stays the same, regardless of the format and even without the lens being put on a camera.

Thanks but I didn't ask for a lecture. I was just saying what I understood the person in the video to have said.

[reh321]

No, there isn't.
Although somewhere in Romania there's a road on which 1 km has 800m; I guess that was an "effective view of length". But unless there's some fraud involved, the length doesn't change.

“Effective focal length” just tells some of us what we see through the viewfinder - what is captured by the sensor. I carry around in my head the fact that my Q-7 has an “effective focal length” roughly three times what my K-30 or KP does,
so I know quickly that my Q-7 will need more than the ‘06 lens {focal length 15-45mm} to capture scene best if 150mm worked best on my KP.

[Class A]

Sigh... no, there is no "effective focal length",

Obviously the physical focal length of a lens never changes.

However, many people equate the angle of view a lens covers with the latter's focal length specification, i.e., a 50mm lens is regarded as a "normal focal length" on an FF camera because it (roughly) produces the perspective that is most natural when viewing the image (e.g., as a print) from a distance that is twice the image diagonal. A certain focal range is regarded as "wide angle" whereas lenses with a focal lengths beyond a certain number are regarded as "telephoto" lenses.

Therefore, because the real value is "angle of view" but people use "focal length" as a shortcut to refer to the former, the shortcut becomes format dependent. A 50mm (actually, 43mm) lens only produces a "normal" (undistorted) perspective on an FF camera. On an APS-C camera, one needs a ~28mm lens, if one wants to make images with the same "normal perspective" property.
It therefore makes sense to regard the focal lengths "43mm" on FF and "28mm" on APS-C as equivalent (meaning, they are not the same, but they produce the same effect).

At 300mm it will show the same angle of view as an APS-C 300mm.

Yes, an angle of view which is achieved by using a ~450mm lens on an FF camera.

There is nothing to debate here. Just like a lens never changing its focal length (regardless of the camera which it is mounted on) is a fact, it is also a fact that one can express the angle of view a certain lens delivers in terms of specifying a focal length (with respect to a format size). You may not find the latter fact helpful but that does not turn it into "nonsense" for everyone.

If people weren't aware of the relevance of converting focal length then a "85mm" would be an "ideal portrait lens" regardless of sensor size (which it isn't) and "lower than 35mm" would be considered "wide angle" regardless of sensor size (which it should definitely not). On APS-C, for instance, "35mm" is even higher than the format's native "normal" focal length, i.e., a 35mm lens on APS-C is far from being a "wide angle" lens.

FWIW, knowing that he crop factor of the Pentax Q7 is ~4.6, one can calculate that the "normal" focal length for the Q7 is ~9.3mm. In other words, the "43mm FF-equivalent" lens on a Q7 is a 9.3mm lens. This is useful.

[JASMAZ77]

yeah some people can't even agree on the proper way on how to spell the unit:



Meter vs. metre – Correct Spelling – Grammarist

Correct way internationally around the world like every country is METRE its only usa that spells it meter which is incorrect.

[MMVIII]

Correct way internationally around the world like every country is METRE its only usa that spells it meter which is incorrect.

Oh my, this thread went down these two rabbitholes now...

Well, like every country outside the US using English or any romanic language... in German it is "Meter", don't know for other germanic languages though, but assume the same. Slavic languages I just know in Slovenian it's meter too. Best compromise would be Russian: metr

[aslyfox]

Obviously the physical focal length of a lens never changes.

However, many people equate the angle of view a lens covers with the latter's focal length specification, i.e., a 50mm lens is regarded as a "normal focal length" on an FF camera because it (roughly) produces the perspective that is most natural when viewing the image (e.g., as a print) from a distance that is twice the image diagonal. A certain focal range is regarded as "wide angle" whereas lenses with a focal lengths beyond a certain number are regarded as "telephoto" lenses.

Therefore, because the real value is "angle of view" but people use "focal length" as a shortcut to refer to the former, the shortcut becomes format dependent. A 50mm (actually, 43mm) lens only produces a "normal" (undistorted) perspective on an FF camera. On an APS-C camera, one needs a ~28mm lens, if one wants to make images with the same "normal perspective" property.
It therefore makes sense to regard the focal lengths "43mm" on FF and "28mm" on APS-C as equivalent (meaning, they are not the same, but they produce the same effect).. . .

if interested

here is an article that can be read:

The Crop Factor Unmasked
Field of View vs Focal Length on various formats
By PF Staff in Articles and Tips on Jul 23, 2014
The Crop Factor Unmasked
Many of us have cameras with different sensor sizes; this raises the question of which lenses need to be used to get the same field of view on two different formats. Below we provide a table listing focal lengths with equivalent Field of View (FoV) across several sensor sizes. The actual diagonal field of view (in degrees) is shown on the far right. Click the table to enlarge. . . .

Read more at: The Crop Factor Unmasked - Articles and Tips | PentaxForums.com

[reh321]

Correct way internationally around the world like every country is METRE its only usa that spells it meter which is incorrect.

"Meter" is correct in American, just as we call the engine covering a "hood", while the British use the term "bonnet"..
A guy named Noah Webster made his famous dictionary because Americans had wandered off from the British
Incidentally, the British also pronounce it differently - putting emphasis on the first syllables, while we put it on the last syllables.