Forgot Password
Pentax Camera Forums Home

Show Printable Version Search this Thread
02-21-2014, 12:55 PM   #31
Site Supporter
Stone G.'s Avatar

Join Date: Jun 2010
Location: North Zealand, Denmark
Photos: Gallery | Albums
Posts: 1,516
QuoteOriginally posted by Na Horuk Quote
Its a whole science
I agree with most of what you have said, but - with all due respect - not this one. I should say lens making is an ART!

It is more like cooking: You know the basic ingredients for a certain meal, but one chef makes it differently from another and results are never quite the same.

Just to illustrate Na Horuk's points about lens designs, I have attached two lens diagrams (FA 50mm f/1.4 and Tamron 01B 24mm f/2.5). It is quite obvious that even "simple primes" aren't that simple after all.

One may note that the entrance pupil of the FA 50mm is 36mm in diameter while the Tamron 24mm has an entrance pupil of 9.6 mm even though the TAMRON has a filter thread of 55 mm while the PENTAX has a "mere" 49mm. See attached photo.

Generally speaking: Making VERY large lenses is costly because it is difficult to cast large specimens without flaws. Making small may be cheap in glass but very demanding in respect of shaping and associated tolerances required.

Attached Images
View Picture EXIF
PENTAX K200D  Photo 
02-21-2014, 01:06 PM   #32
Site Supporter

Join Date: Mar 2009
Location: Gladys, Virginia
Photos: Gallery
Posts: 16,253
QuoteOriginally posted by jon404 Quote
@jogiba -- that is a very interesting picture! Unless I'm wrong, all four lenses are designed to cover a FF sensor. And, as I've learned from this thread, they all produce the same exposure at, say. f/2.8.

So why is the Sigma lens glass so large? As another post noted, lens designers certainly aren't stupid. Off the top, I'd think that the larger glass must cost more to produce that the smaller glass on the other lenses. Is that true? If so -- what optical advantages do they get, if any? Or, is it just a marketing thing aimed at folks like me -- "bigger lens, must give you better pictures?"
A lot has to do with how corrected a lens is and how sharp wide open. A lens like the FA 50 f1.4 may give the same exposure wide open as the Sigma 50mm f1.4, but it will be a lot softer, particularly in the corners. Stopped down a stop or two, you might not be able to tell the difference.
02-21-2014, 07:44 PM   #33
Veteran Member

Join Date: Dec 2012
Photos: Gallery
Posts: 696
Original Poster
Thanks Na, Stone, and Rondec -- what an interesting business! And the more you learn about it, the more fascinating it gets. Perhaps many areas are like this -- automotive design comparisons, or software differences between programs that seem similar but each having some key selling point.

As an consumer, I'm glad that capitalism has prevailed over communism and fascism. It may be silly to have so many competing similar brands, but it sure is fun! And it seems to make for a lot more jobs, even if people are basically making basically the same thing at different enterprises...

  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
aperture, camera, cameras, design, diameter, element, f/2.8, front, iso, k-30, lens, lenses, light, pentax help, photography, sensor, size
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Similar Threads
Thread Thread Starter Forum Replies Last Post
Food It Ain't Much... Rupert Post Your Photos! 19 09-23-2013 06:40 PM
Food It Ain't Lobster! Rupert Post Your Photos! 6 07-18-2012 09:50 AM
If it ain't broke.... starstuff Pentax K-5 23 06-18-2011 08:24 AM
Nature It Ain't Spring Yet shooz Post Your Photos! 4 04-02-2011 05:05 PM
With a name like "Skunk Cabbage" you know it ain't gonnna be pretty NaClH2O Post Your Photos! 9 04-19-2007 07:55 AM

All times are GMT -7. The time now is 01:01 PM. | See also:, part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]