FA Limited Lens' focal length question - Page 2

Alfisti · 08-07-2008, 11:37 AM

Oh it gets better too, we have a solid half dozen key lenses missing from the line up, production is banked up et cetc etc etc ... so they release yet another 35mm lens, we have about 10 lenses that cover 35mm. Mystifying.

VAV · 08-07-2008, 12:17 PM

Thanks to JJJphoto and rparmar for your very educative posts... I need to read that report attached by JJJPphoto once I get home.. and also to gooshin for your comments that drew those responses from the other posters

*jsherman999* · 08-07-2008, 12:35 PM

Originally Posted by JJJPhoto

I don't think that holds water. If that were true then when I hold my K10D with 28mm lens up to my eye and look through the viewfinder I would see the same perspective as I see if I took the camera away and looked with the same one eye.

I don't.

I see more of the scene with ONE eye than I do with a 28mm lens mounted to my K10D.

Even if i move my head (and eye) forward to where the front element of the lens was I still see a wider field of view than the 28mm lens.

There goes that theory.

I don't think we're talking about FOV (field of view) here, we're talking about relative magnification, right? The human FOV is probably something equivalent to 8mm, with resolution dropping sharply beyond the 50mm (film crop) FOV.

Magnification with a 43mm lens is about exactly what you see, as Gooshin was saying.

.

*tranq78* · 08-07-2008, 12:57 PM

Originally Posted by rparmar

The first thing to know is that all numbers on lenses are rounded off. A Canon 50mm might in fact be a 52mm when tested. A Vivitar maximum f/2.8 might actually be f/2.9. But Pentax has this odd-ball impulse to correctly label their gear. So one lens might be released as a f/1.8 and the next f/1.9. Any other manufacturer would let the .1 slide for the sake of consistency and marketing.

Second, 50mm is not the true film normal dimension, it's just an approximation that came to be common. Pentax went back to the drawing board for the FA43. Remember it was the first of the Limited line... the photography world had seen nothing like it for SLRs. It is a completely idiosyncratic lens.

My theory with the FA31 is that they set out to design another 28mm... something conspicuously missing from the contemporary lens line-up, you'll note. But when it came out it of the lab it was a 31mm. Shaving off 3mm would have meant compromising the design. So they didn't.

Ditto the FA77, which might have been designed as a 75mm between the 50mm and 100mm. Just guessing now.

Another way to put this is to say that Pentax makes gear for photographers and not, for example, to appease marketing departments.

aleonx3 · 08-07-2008, 01:40 PM

very interesting and intriguing conversation; and very educational too, I might add. Thanks OP for such an interesting topic. Reminds me that I once quoted someone who asked me why I did not choose the C* brand, I say I want to have that 77mm lens. He thinks that I was weird as he thinks that there is no such lens existing.

*KFrog* · 08-07-2008, 02:20 PM

Originally Posted by aleonx3

very interesting and intriguing conversation; and very educational too, I might add. Thanks OP for such an interesting topic. Reminds me that I once quoted someone who asked me why I did not choose the C* brand, I say I want to have that 77mm lens. He thinks that I was weird as he thinks that there is no such lens existing.

I love that answer.

*rparmar* · 08-07-2008, 02:28 PM

Originally Posted by aleonx3

I once quoted someone who asked me why I did not choose the C* brand, I say I want to have that 77mm lens. He thinks that I was weird as he thinks that there is no such lens existing.

I must admit the odd numbers totally appeal to me. Maybe that's why I've got a Vivi 105mm.

OK, well, there are other reasons to own that and the FA Limiteds. A few reasons.

Pål Jensen · 08-07-2008, 05:22 PM

Originally Posted by VAV

I am curious about how Pentax came up with the focal lengths for the three FA limited lens - 31, 43 and 77 - How do they decide on these focal lengths ?- why not, for example, 30-50-75?

Thanks

The first Limited lens was a private(?

) project between Pentax chief lens designer, Harakawa(?

) and the famous Japanese photographer Shoji Ueda(I think it was but may be wrong

). The focal lenght is the true normal lens for the 35mm system; diagonal 43mm. They wanted to mimic the pleasant rendering qualities of the pre computer age lens designs. They used a lot of trial and error. Thats why the 43 Limted have quite large amounts of distortions as it contribute to its rendering qualities.
The 77 Limited was obviously to fill the need for a Limited short telephoto. The rumor has it that it was presented to Ueda(?

) on his 77th birthday. Thats why it is 77mm. In reality, rumor again has it, it is indeed a 79mm lens

.
The 31mm designed by another team

. Its focal lenght choice, except for being ideal focal lenght for landscapes - something I tend to agree with - is unknown (to me

). Its rendering philosophy likewise...

There were also a FA 118/2,4(or 2.8?

) Limited. And a 90/3.5 Macro Limited that went to 1:2 by itself. 1:1 with matching (Limited) close focus lens or small Limited extenstion tube (which one wasn't decided upon yet when got the information) included with the lens. Needless to say, neither saw the light of day....
My guess is that there was a Limited wide angle wider than the 31mm, but haven't heard anything about that one...

VAV · 08-08-2008, 06:30 AM

Originally Posted by Pål Jensen

The first Limited lens was a private(?) project between Pentax chief lens designer, Harakawa(?) and the famous Japanese photographer Shoji Ueda(I think it was but may be wrong). The focal lenght is the true normal lens for the 35mm system; diagonal 43mm. They wanted to mimic the pleasant rendering qualities of the pre computer age lens designs. They used a lot of trial and error. Thats why the 43 Limted have quite large amounts of distortions as it contribute to its rendering qualities.
The 77 Limited was obviously to fill the need for a Limited short telephoto. The rumor has it that it was presented to Ueda(?) on his 77th birthday. Thats why it is 77mm. In reality, rumor again has it, it is indeed a 79mm lens.
The 31mm designed by another team. Its focal lenght choice, except for being ideal focal lenght for landscapes - something I tend to agree with - is unknown (to me). Its rendering philosophy likewise...

There were also a FA 118/2,4(or 2.8?) Limited. And a 90/3.5 Macro Limited that went to 1:2 by itself. 1:1 with matching (Limited) close focus lens or small Limited extenstion tube (which one wasn't decided upon yet when got the information) included with the lens. Needless to say, neither saw the light of day....
My guess is that there was a Limited wide angle wider than the 31mm, but haven't heard anything about that one...

Thanks Pal Jensen - this seems to fill in some interesting details on NaCL's previous post.

Alfisti · 08-08-2008, 06:44 AM

Is the 77 really 79? If the 70 is really 68 then there is 11mm difference not 7mm. It explains a few things.

*rparmar* · 08-08-2008, 08:02 AM

Originally Posted by Alfisti

Is the 77 really 79? If the 70 is really 68 then there is 11mm difference not 7mm. It explains a few things.

I have read this a couple of times, with the 77mm being claimed as 80mm or whatever. Does anyone have the tests where this was determined?

IOW, proof would be nice.

RBellavance · 08-08-2008, 09:28 AM

Another interesting tidbit is that if you *divide* the FA Ltds' focal lengths by 1.5, you get "standard" 135 format focal lengths:

77mm becomes 50mm (i.e. a normal)
43mm becomes 28mm (i.e. a wide-angle)
31mm becomes 20mm (i.e. an ultra wide-angle)

It almost seems like the FAs had originally been designed for a larger-than-135 format

Miserere · 08-08-2008, 01:27 PM

Originally Posted by jsherman999

I don't think we're talking about FOV (field of view) here, we're talking about relative magnification, right? The human FOV is probably something equivalent to 8mm, with resolution dropping sharply beyond the 50mm (film crop) FOV.

Magnification with a 43mm lens is about exactly what you see, as Gooshin was saying.

.

J, that's almost correct. In fact, magnification with a 43mm isn't 1:1, that's what 50mm lenses are for.

A 50mm lens offers no magnification, like someone already pointed out. This isn't some magic quality of 50mm lenses, it's a standard decided by the camera manufacturers at some point in the distant past. It doesn't matter what camera you put a 50mm lens on, be it 35mm, APS-C or 4x5, magnification will always be ZERO (or 1, or 100%, depending how you want to define magnification). What WILL BE different is the FoV; APS-C will have the smallest, then 35mm, and 4x5 will have the largest.

Ever wondered why the viewfinders of APS-C cameras are so small compared to 35mm? It's because the both have the same magnification but the FoV of the APS-C camera is 1.5 times smaller, so the viewfinder has to also be 1.5 times smaller.

Gooshin · 08-08-2008, 01:32 PM

Originally Posted by Miserere

Ever wondered why the viewfinders of APS-C cameras are so small compared to 35mm? It's because the both have the same magnification but the FoV of the APS-C camera is 1.5 times smaller, so the viewfinder has to also be 1.5 times smaller.

weeellllllll

they COULD have made a mirror and viewfinder the same size as a 35mm SLR, and then simply etch a border in the focusing screen to let you know where your APC's sensor limits are.

its not totaly out of the question...

Miserere · 08-08-2008, 01:34 PM

As for focal lengths of the Ltds, 43mm is the normal focal length (FL) for 35mm film, like has been pointed out. 31mm is then about 1 FL-stop wider than 43mm, meaning the FoV is about 50% larger. 77mm is the odd one, as 1 FL-stop would be 61mm and 2 FL-stops would be 86mm; 77mm is about 1-2/3 stops longer than 43mm.