31 mm ltd
Posted 15/12/2010 - 23:21
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The 31mm gets very close to an equivalent std focal length on a cropped sensor.
Maybe pentax new that?
Maybe they wanted a 70' FOV on a 35mm format?
Best regards
Maybe pentax new that?
Maybe they wanted a 70' FOV on a 35mm format?
Best regards
Too far from a shore.
Posted 15/12/2010 - 23:23
Link
My guess is it's nominally halfway between 28 and 35. I wondered some time ago how the focal length range came about. this is what I came up with. Each number is half way between it's neighbours
Progression Pentax AF Range
784
588 600
392 400
294 300
196 200
168
140 135
112
98 100
84 85
77 77
70 70
56 55
50 50
42 43
40 40
38
35 35
31 31
28 28
24 24
21 21
20 20
18
16
15 15
14 14
Progression Pentax AF Range
784
588 600
392 400
294 300
196 200
168
140 135
112
98 100
84 85
77 77
70 70
56 55
50 50
42 43
40 40
38
35 35
31 31
28 28
24 24
21 21
20 20
18
16
15 15
14 14
Barrie - Too Old To Die Young
https://pentaxphotogallery.com/artists/barrieforbes
https://www.flickr.com/photos/189482630@N03/
https://pentaxphotogallery.com/artists/barrieforbes
https://www.flickr.com/photos/189482630@N03/
Posted 15/12/2010 - 23:29
Link
They are just being honest perhaps. Traditionally, focal lengths as marked are just approximations, and of course some manufacturers will try to make things look better than they are.
Most 1970s and earlier 24mm lenses are more like 25mm. Only Zeiss admit this I think.
Zooms are wide open to abuse - after all a 28-80mm zoom sounds much better than a 29-77mm one!
Most 1970s and earlier 24mm lenses are more like 25mm. Only Zeiss admit this I think.
Zooms are wide open to abuse - after all a 28-80mm zoom sounds much better than a 29-77mm one!
Best regards, John
Posted 15/12/2010 - 23:30
Link
Well, I don't exactly know but I'll guess..
They started with 43 which was "true normal" (43mm is diagonal of 35mm film format). For tele they opted for 77/1.8 (size and weight of M85/2 with marginally narrower DOF) I guess to keep away from 85 (they already had FA*85/1.4) yet long enough for portraits and fast enough for shallow DOF. These two are great compromise between speed and size/weight. They needed wide lens to complete the line up. Now what do you do? You have 28/2.8 and 35/2 out there. Sigma was already (I believe) doing 28/1.8. So what do you do to be different? Make a lens slap bang in the middle, as fast as competition but smaller. E voila.... 31/1.8 was born. Some think it's a big lens, but just put it next to 28/1.8 or old K28/2 and you'll know better!
disclaimer: all above is pure speculation on my behalf...
oh and one more reason:
So Pentax folks could say: we have the best AF lens by anyone outhere
They started with 43 which was "true normal" (43mm is diagonal of 35mm film format). For tele they opted for 77/1.8 (size and weight of M85/2 with marginally narrower DOF) I guess to keep away from 85 (they already had FA*85/1.4) yet long enough for portraits and fast enough for shallow DOF. These two are great compromise between speed and size/weight. They needed wide lens to complete the line up. Now what do you do? You have 28/2.8 and 35/2 out there. Sigma was already (I believe) doing 28/1.8. So what do you do to be different? Make a lens slap bang in the middle, as fast as competition but smaller. E voila.... 31/1.8 was born. Some think it's a big lens, but just put it next to 28/1.8 or old K28/2 and you'll know better!
disclaimer: all above is pure speculation on my behalf...
oh and one more reason:
So Pentax folks could say: we have the best AF lens by anyone outhere
Posted 16/12/2010 - 00:39
Link
K10D wrote:
The 31mm gets very close to an equivalent std focal length on a cropped sensor.
Maybe pentax new that?
Maybe they wanted a 70' FOV on a 35mm format?
Best regards
Was that new or knew Gary?The 31mm gets very close to an equivalent std focal length on a cropped sensor.
Maybe pentax new that?
Maybe they wanted a 70' FOV on a 35mm format?
Best regards
Must learn grammar!
Too far from a shore.
Posted 16/12/2010 - 01:04
Link
johnriley wrote:
They are just being honest perhaps. Traditionally, focal lengths as marked are just approximations, and of course some manufacturers will try to make things look better than they are.
Most 1970s and earlier 24mm lenses are more like 25mm. Only Zeiss admit this I think.
Zooms are wide open to abuse - after all a 28-80mm zoom sounds much better than a 29-77mm one!
good points and while there is no need to tell you this, JR some others might be surprised to learn that most zooms are vari-focal lenses that regardless of indicated focal length on the lenses, the focal length actually changes as the lens focuses. This is especially noticeable in wide range zooms like the 28-200's....
They are just being honest perhaps. Traditionally, focal lengths as marked are just approximations, and of course some manufacturers will try to make things look better than they are.
Most 1970s and earlier 24mm lenses are more like 25mm. Only Zeiss admit this I think.
Zooms are wide open to abuse - after all a 28-80mm zoom sounds much better than a 29-77mm one!
Fired many shots. Didn't kill anything.
Posted 16/12/2010 - 10:17
Link
Don wrote:
good points and while there is no need to tell you this, JR some others might be surprised to learn that most zooms are vari-focal lenses that regardless of indicated focal length on the lenses, the focal length actually changes as the lens focuses. This is especially noticeable in wide range zooms like the 28-200's....
The focal length quoted for any lens is the focal length at infinity. They all change as you focus closer
good points and while there is no need to tell you this, JR some others might be surprised to learn that most zooms are vari-focal lenses that regardless of indicated focal length on the lenses, the focal length actually changes as the lens focuses. This is especially noticeable in wide range zooms like the 28-200's....
Half Man... Half Pentax ... Half Cucumber
Pentax K-1 + K-5 and some other stuff
Algi
Pentax K-1 + K-5 and some other stuff
Algi
Posted 16/12/2010 - 10:19
Link
K10D wrote:
Was that new or knew Gary?
Must learn grammar!
MZS, 15mm f/3.5
Your only as good as your last shot
^^^^
Oh dear. Was that "your" (as in 'it belongs to you') or "you're" (as in 'you are')?
Was that new or knew Gary?
Must learn grammar!
MZS, 15mm f/3.5
Your only as good as your last shot
^^^^
Posted 16/12/2010 - 10:21
Link
Because it's a prime number
Typo, word blind, ...
be glad it's not SMS speak
K10D wrote:
Was that new or knew Gary?
Must learn grammar!
Bull...Was that new or knew Gary?
Must learn grammar!
Typo, word blind, ...
be glad it's not SMS speak
Pentax K10D + Vivitar 55/2.8 macro + Super Takumar 55/1.8 + SuperMultiCoated Takumar 85/1.8 + SuperMultiCoated Takumar 135/3.5 + SuperMultiCoated Takumar 200/4 + Super Takumar 300/4
Pentax K100D + DA18-55ALII + DA55-300
Pentax K5 + FA31Ltd + M50/1.7 + DFA100WR + M120/2.8 (+ DA18-55WR at occasion)
Pentax K100D + DA18-55ALII + DA55-300
Pentax K5 + FA31Ltd + M50/1.7 + DFA100WR + M120/2.8 (+ DA18-55WR at occasion)
Posted 16/12/2010 - 10:27
Link
txt spk sterretje
Z-1p, K-1, P50
F50 1.7. SMC-FAs 24, 35, 50 1.4, 85, 135. HD-FA15-30, DFA24-70, D-FA*70-200. The SMC-FA Limited Trinity.
Metz 45 CL-4, AF500FTZ. AF540FGZ.
Some Mamiya and some Nikon, and a Canon T70.
F50 1.7. SMC-FAs 24, 35, 50 1.4, 85, 135. HD-FA15-30, DFA24-70, D-FA*70-200. The SMC-FA Limited Trinity.
Metz 45 CL-4, AF500FTZ. AF540FGZ.
Some Mamiya and some Nikon, and a Canon T70.
Posted 16/12/2010 - 10:40
Link
Apparently 77mm was chosen because the number 7 is considered lucky in Japan (hence the K7 with its 77 segment metering and 77 weather seals).
Joining the Q
Posted 16/12/2010 - 19:01
Link
Maybe they just wanted a prime lens with a prime number focal length?
MZ
MZ
K5, K7, Nikon FA.
AF Lenses: DA15mm Ltd, DA21mm Limited, DA35mmAL, DA50mm f1.8, DA18-55mmWR, FA28-70mm f4AL, DA50-200mmWR,Tamron SP70-200mm f2.8, AF70-300mm LD Di, SP10-24mm, SP90mm Macro.
MF Lenses: SMC-A 50mm, Adaptall 24mm(CW-24), 135mm(03B), 35-70mm(17A) 80-210mm(03A), Micro-Nikkor55mm, Soligor I-S 200mm f2.8 AIS
My Flickr - link
My Photobucket - link
AF Lenses: DA15mm Ltd, DA21mm Limited, DA35mmAL, DA50mm f1.8, DA18-55mmWR, FA28-70mm f4AL, DA50-200mmWR,Tamron SP70-200mm f2.8, AF70-300mm LD Di, SP10-24mm, SP90mm Macro.
MF Lenses: SMC-A 50mm, Adaptall 24mm(CW-24), 135mm(03B), 35-70mm(17A) 80-210mm(03A), Micro-Nikkor55mm, Soligor I-S 200mm f2.8 AIS
My Flickr - link
My Photobucket - link
Posted 16/12/2010 - 19:44
Link
Maybe it was marketing.... even if it was not intentional, these unusual focal lengths stand out.
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