Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
06-26-2007, 08:11 PM   #1
Inactive Account




Join Date: Jun 2007
Location: Gippsland, Victoria, Australia
Photos: Albums
Posts: 66
Question about K100D lenses

Hi, I am new here, and firstly I have to say THANKYOU all

I have been reading through info for the past few days, and it is great to see how great you all are with sharing info and encouraging each other. It is so nice to find a place where others know how to use my camera!!

I have been using pentax cameras pretty much since I got into photography . . . I am just an amateur 'family' photographer, who likes taking photos!

I recently, a week ago infact, bought my first dSLR - a K100D (I have a MZ-50 and an MZ-7 also) . . . I think I am going to love it. (I had a compact digital which died, and didn't want to replace it until I could afford an SLR).

Anyway . . . my question!!

I know that there is a 1.5X magnification factor when I use my other lenses on the K100D, but I am not sure about the digital specific lenses that came with the camera.

What I want to know is . . . the 18-50 DC (sigma lens for digital cameras) that came with the camera, IS it 18-50, or is it infact equivalent to 28-75 like the other lenses??

Does my question make sense??
I am trying to work out what range lenses I 'actually' have!!!
And thank you to those who take the time to answer . . . I appreciate it

06-26-2007, 08:32 PM   #2
Veteran Member




Join Date: Jun 2007
Location: Owego, NY
Posts: 976
QuoteOriginally posted by JLou Quote
Hi, I am new here, and firstly I have to say THANKYOU all

I have been reading through info for the past few days, and it is great to see how great you all are with sharing info and encouraging each other. It is so nice to find a place where others know how to use my camera!!

I have been using pentax cameras pretty much since I got into photography . . . I am just an amateur 'family' photographer, who likes taking photos!

I recently, a week ago infact, bought my first dSLR - a K100D (I have a MZ-50 and an MZ-7 also) . . . I think I am going to love it. (I had a compact digital which died, and didn't want to replace it until I could afford an SLR).

Anyway . . . my question!!

I know that there is a 1.5X magnification factor when I use my other lenses on the K100D, but I am not sure about the digital specific lenses that came with the camera.

What I want to know is . . . the 18-50 DC (sigma lens for digital cameras) that came with the camera, IS it 18-50, or is it infact equivalent to 28-75 like the other lenses??

Does my question make sense??
I am trying to work out what range lenses I 'actually' have!!!
And thank you to those who take the time to answer . . . I appreciate it
The numbers are its actual focal length, not it's "35mm effective" focal length.

The only difference is that the DAs have a smaller image circle (which allows Pentax to make a lens with a short FL more easily).
06-26-2007, 08:34 PM   #3
Veteran Member
Kguru's Avatar

Join Date: Jun 2007
Location: Perth - WestAust
Posts: 602
If mounted on a 35mm film camera it's 18-50 as given.
If mounted on digital camera with 1.5x then it's 27-75 equivalent.
06-26-2007, 08:46 PM   #4
Inactive Account




Join Date: Jun 2007
Location: Gippsland, Victoria, Australia
Photos: Albums
Posts: 66
Original Poster
Thanks for your quick responses

You answered what I thought would be the answer
I guess I was just confused because the digital lenses can't be used on the film SLR cameras!

Again . . . thanks

06-26-2007, 11:40 PM   #5
Pentaxian




Join Date: Sep 2006
Location: Kaunas
Posts: 1,452
QuoteOriginally posted by Kguru Quote
If mounted on a 35mm film camera it's 18-50 as given.
If mounted on digital camera with 1.5x then it's 27-75 equivalent.
Well, to be precise, it stays 18-50mm wherever it is mounted on. Focal length is lens characteristic and doesn't depend on anything else.
06-27-2007, 12:04 AM   #6
baw
Senior Member




Join Date: Dec 2006
Location: Neterlands
Posts: 189
Actually the lens characteristics don't change when mounted on a smaller sensor.
The Field of View changes and looks like the 1.5X equivalent.
DOF etc. stay the same.

example my Nikon 5700 has an 8 - 70 mm lens and a 4x "cropfactor". (approximately)
FOV is like a 32-280 lens on a 35mm. camera, but DOF is still as is to be expected from a 8-70mm lens.
06-27-2007, 02:28 AM   #7
Veteran Member




Join Date: Mar 2007
Location: Queensland, Australia
Posts: 668
QuoteOriginally posted by Entropy Quote
The only difference is that the DAs have a smaller image circle (which allows Pentax to make a lens with a short FL more easily).
They also save materials (and therefore weight) and cost.
06-27-2007, 03:58 PM   #8
Veteran Member




Join Date: Jun 2007
Location: Owego, NY
Posts: 976
QuoteOriginally posted by SupremeMoFo Quote
They also save materials (and therefore weight) and cost.
True, that too.

If you compare the DA 50-200 compared to anything that covers that zoom/aperture range and has an image circle that supports full frame cameras, the FF lens will be far heavier and more expensive, and often have lower image quality. (Like my Sigma 28-200 from the old film days, which will be replaced by the DA 50-200 as soon as UPS delivers it. )

06-27-2007, 04:05 PM   #9
Inactive Account




Join Date: Jun 2007
Posts: 264
To be fair the 28-200 will have lower image quality... because it is a 28-200, not because it's designed for the 35mm format.
06-27-2007, 04:17 PM   #10
Senior Member




Join Date: Nov 2006
Location: Portland, Oregon
Photos: Gallery
Posts: 217
1) Remember so far all lenses are marketed with their actual focal lengths.

2) The lens does not change depending on what is attached to.

3) the question is how much of the scene is recorded by the camera... not by the lens... by the camera.

digicam < Dslr < 35mm < 645 MF < 6x7 MF < 8x10LF .... the crop factor is marketing trying to explain how the Dslr behaves differently than your old SLR.

So if you mount a 50mm lens on your MZ-7 it will record a "normal" view, but if you mount the lens on the K100, a smaller field of view is recorded. the edges get "cropped" out. To get the same field of view on the K100, you should try the FA35/2

(But if you get the same field of view from the same vantage point, you will get greater depth of field since you used a shorter focal length.)
Reply

Bookmarks
  • 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!
camera, cameras, dslr, info, k100d, lenses, photography, question
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
K100D IR Conversion QUestion Tyler Pentax DSLR Discussion 4 09-28-2008 07:42 AM
K100d Flash question cathynwv Pentax DSLR Discussion 10 05-21-2008 10:21 PM
K100D Super Question Tuner571 Pentax DSLR Discussion 3 03-09-2008 12:28 PM
New K100D Question Romoman Pentax DSLR Discussion 5 07-08-2007 10:12 PM
K100D question about AE lock leaton Pentax DSLR Discussion 3 10-07-2006 09:55 PM



All times are GMT -7. The time now is 12:10 PM. | See also: NikonForums.com, CanonForums.com 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?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top