Re: FA 24-90 focal length
Did you check the short end? Wouldn't be interesting if it was just another 28-80? BTW, nominal and actual focal lengths have always been somewhat problematic, but 10+% is a bit out of line. Ciao, Graywolf http://pages.prodigy.net/graywolfphoto - Original Message - From: keller.schaefer [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Thursday, July 03, 2003 9:29 AM Subject: FA 24-90 focal length Some weeks ago I inquired here about the FA 24-90 lens quality. Subsequently I bought the lens and shot some film with it. I would rate the optical quality as very reasonable and the mechanical quality as not-so-good. What puzzled me was the fact that when looking through the viewfinder the lens in the longest '90' mm position still had a shorter (!) focal lenth than my M 2,0/85. I tried to verify this by mounting the remnants of an old ME Super K-mount to the lens standard of a view camera and attaching the lens to it. As the difference in distance between lens and film (when moving the lens from infinity to 1:1 magnification) equals the focal length, I was able to measure this with some precision. The longest focal length turned out to be 81 mm (I'd say plus or minus 1 mm). I have also tested some other Pentax lenses: M 2,0/35: 34,8 mm M 1,4/50: 49,2 mm M 2,0/85: 83,9 mm M 2,8-4/40-80 at 80 mm: 78,9 mm and found these are quite close to what the lens designation says. Pentax Germany did not dispute my measurements but admitted that the 90 mm designation is an exaggeration for competitive reasons (...everybody does it like that). So, effectively, this lens is an 24-80. I thought you might be interested. Sven
re: FA 24-90 focal length
Sven, I'm not familiar with your measuring system, but are you able to check the focal length at various focusing distances? Some internal focusing (IF) lenses are known to have shorter effective focal lengths at shorter distances. The FA 28-200 is around 180mm at infinity, but more like 110 mm at around 2 meters, as tested by Keppler at Popular Photography. Most other Pentax lenses are much closer to the specified focal length. Thanks for the info, Sven, it is of interest. Pat White
Re: FA 24-90 focal length
Sven wrote: ks As ks the difference in distance between lens and film (when moving the lens from ks infinity to 1:1 magnification) equals the focal length, I was able to measure ks this with some precision. Sven, this may be valid with older lenses design, but nowadays modern lenses focus at close distances by shorting the focal length. The odds are that your lens is near 90mm at infinity and drops towards 80mm at the shortest focus distance. Servus, Alin
re: FA 24-90 focal length
The difference between infinity and 1:1 is the focal length of any lens, by definition. I had blocked the lens (with tape) in the infinity position (verified by looking through the finder) so - more precisely - I should have stated that what I measured is the focal length in the infinity position. With internal focusing, away from infinity, the lens effectively becomes 'a different lens'. So it may well be that when set to closer distances the focal length is different... but at infinity it is significantly less than 90 mm. The short end of the lens seemed to be o.k., but at short focal lengths it becomes difficult to adjust the lens to exact 1:1 magnification, so I did not measure this. Sven Zitat von Pat White [EMAIL PROTECTED]: Sven, I'm not familiar with your measuring system, but are you able to check the focal length at various focusing distances? Some internal focusing (IF) lenses are known to have shorter effective focal lengths at shorter distances. The FA 28-200 is around 180mm at infinity, but more like 110 mm at around 2 meters, as tested by Keppler at Popular Photography. Most other Pentax lenses are much closer to the specified focal length. Thanks for the info, Sven, it is of interest. Pat White
Re: FA 24-90 focal length
on 03.07.03 15:29, keller.schaefer at [EMAIL PROTECTED] wrote: What puzzled me was the fact that when looking through the viewfinder the lens in the longest '90' mm position still had a shorter (!) focal lenth than my M 2,0/85. I tried to verify this by mounting the remnants of an old ME Super K-mount to the lens standard of a view camera and attaching the lens to it. As the difference in distance between lens and film (when moving the lens from infinity to 1:1 magnification) equals the focal length, I was able to measure this with some precision. [...] So, effectively, this lens is an 24-80. Interesting. But read test of this lens in Popular Photography: http://www.popphoto.com/article.asp?section_id=2article_id=327 They rate 24-90 as 24.42-87.14 mm in reality. Who is right? Also, have you tried 24-90 at different focusing distances? Internal focusing AFAIK changes a bit focal length, so maybe here is the point? -- Best Regards Sylwek
Re: FA 24-90 focal length
Yes, the old FA Power Zoom 28-105 actually went to 101 mm. The Sigma AF 70-200 f2.8 actually goes to 190 mm. or so. It is common practice. Still I regard the FA 24-90 as a fine lens. Like you, I do not care for the built quality. Joe
Re: FA 24-90 focal length
Hallo, I just put my FA 1.4/85 and my 24-90 on my camera and compared the field of view on 85 and 90 at infinity. The zoom has a longer focal lenght than the 85, maybe 88? I think that the FA* 85 has a focal lenght of about 85. I compared it also to the FA 2/24. There it looked the same. I think the zoom is longer as 80. Ones I have measured my SMC-F 28-80 and it was 77 at the long end. I do not know how you did your measurement, but I think the 24-90 is not far from the specs. regards Rüdiger Von: keller.schaefer [EMAIL PROTECTED] Some weeks ago I inquired here about the FA 24-90 lens quality. Subsequently I bought the lens and shot some film with it. I would rate the optical quality as very reasonable and the mechanical quality as not-so-good. What puzzled me was the fact that when looking through the viewfinder the lens in the longest '90' mm position still had a shorter (!) focal lenth than my M 2,0/85. I tried to verify this by mounting the remnants of an old ME Super K-mount to the lens standard of a view camera and attaching the lens to it. As the difference in distance between lens and film (when moving the lens from infinity to 1:1 magnification) equals the focal length, I was able to measure this with some precision. The longest focal length turned out to be 81 mm (I'd say plus or minus 1 mm). I have also tested some other Pentax lenses: M 2,0/35: 34,8 mm M 1,4/50: 49,2 mm M 2,0/85: 83,9 mm M 2,8-4/40-80 at 80 mm: 78,9 mm and found these are quite close to what the lens designation says. Pentax Germany did not dispute my measurements but admitted that the 90 mm designation is an exaggeration for competitive reasons (...everybody does it like that). So, effectively, this lens is an 24-80. I thought you might be interested. Sven
Re: FA 24-90 focal length
I always knew my FA77 is actually a FA85. :-) regards, Alan Chan Some weeks ago I inquired here about the FA 24-90 lens quality. Subsequently I bought the lens and shot some film with it. I would rate the optical quality as very reasonable and the mechanical quality as not-so-good. What puzzled me was the fact that when looking through the viewfinder the lens in the longest '90' mm position still had a shorter (!) focal lenth than my M 2,0/85. I tried to verify this by mounting the remnants of an old ME Super K-mount to the lens standard of a view camera and attaching the lens to it. As the difference in distance between lens and film (when moving the lens from infinity to 1:1 magnification) equals the focal length, I was able to measure this with some precision. The longest focal length turned out to be 81 mm (I'd say plus or minus 1 mm). I have also tested some other Pentax lenses: M 2,0/35: 34,8 mm M 1,4/50: 49,2 mm M 2,0/85: 83,9 mm M 2,8-4/40-80 at 80 mm: 78,9 mm and found these are quite close to what the lens designation says. Pentax Germany did not dispute my measurements but admitted that the 90 mm designation is an exaggeration for competitive reasons (...everybody does it like that). So, effectively, this lens is an 24-80. I thought you might be interested. Sven _ Help STOP SPAM with the new MSN 8 and get 2 months FREE* http://join.msn.com/?page=features/junkmail
Re: FA 24-90 focal length
On 3 Jul 2003 at 16:50, Sylwester Pietrzyk wrote: on 03.07.03 15:29, keller.schaefer at [EMAIL PROTECTED] wrote: Interesting. But read test of this lens in Popular Photography: http://www.popphoto.com/article.asp?section_id=2article_id=327 They rate 24-90 as 24.42-87.14 mm in reality. Who is right? Also, have you tried 24-90 at different focusing distances? Internal focusing AFAIK changes a bit focal length, so maybe here is the point? At a 3m subject distance my A*85/1.4 definitely shows narrower field of view than my FA24-90 at 90mm. However what I noticed is that the magnification seems far more affected by focal distance using the zoom so at an effective infinity subject distance it may well measure more like 90mm (or ~87mm) Rob Studdert HURSTVILLE AUSTRALIA Tel +61-2-9554-4110 UTC(GMT) +10 Hours [EMAIL PROTECTED] http://members.ozemail.com.au/~distudio/publications/ Pentax user since 1986, PDMLer since 1998
