Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
6 Days Ago   #1
Senior Member




Join Date: Feb 2018
Posts: 105
Tele converter

Back in the old days I purchased vivitar 2x converter but never took the time to learn how to use it. I knew that it was supposed to double your lens from say 50mm to 100mm but that is about it. I remember hearing somewhere (right) that if you used one it effected your aperture settings. Anybody out there willing to set me on the road to find out.

6 Days Ago   #2
Seeker of Knowledge
Loyal Site Supporter
aslyfox's Avatar

Join Date: Aug 2016
Location: Topeka, Kansas
Photos: Gallery | Albums
Posts: 18,903
some times an encyclopedia ( wiki in digital age ) is good for basic knowledge:

QuoteQuote:
Teleconverter
From Wikipedia, the free encyclopedia

A teleconverter (sometimes called tele extender) is a secondary lens mounted between a camera and a photographic lens which enlarges the central part of an image obtained by the objective lens. A 2 teleconverter for a 35 mm camera would enlarge the central 1218 mm part of an image to the size of 2436 mm in the standard 35 mm film format.

Teleconverters are typically made in 1.4, 1.7, 2 and 3 variants, with 1.4 and 2 being the most common. A 2 teleconverter effectively doubles the focal length of a given lens. Teleconverters also decrease the intensity of the light that reaches the film plane (or sensor) by the square of its magnification. A 2 teleconverter reduces the light to 1/4, doubles the focal ratio and halves the resolution of an image . . . .
Teleconverter - Wikipedia
QuoteQuote:
Pentax-DA 1.4x AW AF Rear Converter
Introduction
Pentax released the long-awaited 1.4x autofocus teleconverter in March, 2014. This handy accessory mounts between your existing DSLR lens and the camera mount to increase the effective focal length by 1.4x, giving you extra reach at the expense of one stop of light. For example, a 300mm F4 lens paired with the teleconverter would give you the same field of view and maximum aperture as a 420mm F5.6 lens. We feel that the teleconverter is an important addition to the Pentax lens lineup, which currently has a limited number of extreme telephoto lenses.


Read more at: Pentax-DA 1.4x AW AF Rear Converter Review - Introduction | PentaxForums.com Reviews
6 Days Ago   #3
Pentaxian




Join Date: Sep 2012
Location: NY
Photos: Gallery | Albums
Posts: 4,095
Supposedly the amount of light that enters the camera is limited more when you apply the converter. That is why the user may have to resort to a lower number aperture to allow more light in than would be required if a converter was not being used.
6 Days Ago   #4
Site Supporter
Site Supporter




Join Date: Jul 2011
Location: Melbourne
Photos: Gallery | Albums
Posts: 666
Easy 2x ones lose 2 stops of light so if your original lens is a 2.8 then the effective f stop becomes f5.6
then 1.4x ones lose 1 stop so the 2.8 then becomes f4
The quality of result depends on the quality of the teleconverter, always worth trying out, enjoy

6 Days Ago   #5
Seeker of Knowledge
Loyal Site Supporter
aslyfox's Avatar

Join Date: Aug 2016
Location: Topeka, Kansas
Photos: Gallery | Albums
Posts: 18,903
what

have fun with photography

I guess that is one option:


QuoteQuote:
How to Use a Teleconverter
Everything you need to know about teleconverters
BY NASIM MANSUROV 128 COMMENTS
LAST UPDATED ON APRIL 24, 2020

. . .

Table of Contents
What is a Teleconverter?
Optical Design
Common Teleconverters
How to Mount and Use a Teleconverter
Teleconverter Lens Compatibility
Coupling Teleconverters with Prime vs Zoom Lenses
The Pros and Cons of Using Teleconverters
Focal Length Versatility
No Change in Minimum Focus Distance
Image Degradation with Teleconverters
Reduced Sharpness
Reduced Contrast
Impact to Lens Calibration
Reduced Autofocus Performance
Teleconverters vs Extension Tubes
Teleconverter vs Cropping in Post
Teleconverter vs Cropping in Camera
Nikon Teleconverter Overview
Sony Teleconverter Overview
Teleconverter FAQ
\\https://photographylife.com/what-is-a-teleconverter

5 Days Ago   #6
dms
Site Supporter
Site Supporter




Join Date: Aug 2011
Location: New York, NY
Photos: Gallery
Posts: 1,964
Since the TC enlarges the image, the part that reaches the film/sensor is lower in intensity. A 1.4x TC enlarges linear dimension by 40% and thus the total area (if it was all captured) is double [1.4 x 1.4 ~2], thus the light intensity is 1/2 and thus 1 stop more exposure is required. If a 2x TC, the area is 2 x 2 =4 or 1/4 the intensity, and thus 2 stop more exposure is required.
5 Days Ago   #7
Forum Member




Join Date: Feb 2012
Location: Columbus Ohio USA
Posts: 60
I had a albinar. In my experience I get better results not using it and cropping the photo (k3 user). I ended up removing the glass and I use it as a macro tube
5 Days Ago   #8
Loyal Site Supporter
Loyal Site Supporter
UncleVanya's Avatar

Join Date: Jul 2014
Photos: Gallery | Albums
Posts: 16,665
Cheap teleconverters degrade the image too much. In the film era they were acceptable often but in digital only the high quality ones are worth using vs cropping.

5 Days Ago   #9
Loyal Site Supporter
Loyal Site Supporter
i_trax's Avatar

Join Date: Jan 2011
Location: Perth Western Australia
Photos: Gallery | Albums
Posts: 1,352
Tamron SP F 1.4x AF is my most used teleconverter, it is Full Frame
Occasionally I use Pentax HD DA 1.4X AW AF cropped sensors only and Vivitar 2x Macro PKA ( for MACRO photos )
I also have Tamron SP F 2x AF , never use it.
5 Days Ago   #10
Site Supporter
Site Supporter




Join Date: Oct 2018
Location: Quebec
Posts: 1,018
645 FA 200 mm f/4 alone VS 645 FA 200 mm f/4 + 645 1.4 X converter.



5 Days Ago   #11
Pentaxian
Lord Lucan's Avatar

Join Date: Sep 2017
Location: South Wales
Photos: Gallery
Posts: 754
I think in terms of an equivalent simple lens. The F number is the focal length divided by the diameter of the lens.


When you add a teleconverter you are changing the focal length but not changing the lens diameter. So if the converter doubles the focal length, you double the F number.

Last edited by Lord Lucan; 5 Days Ago at 12:21 PM.
5 Days Ago   #12
Site Supporter
Site Supporter




Join Date: Dec 2015
Location: Goldsboro North Carolina
Photos: Gallery | Albums
Posts: 1,481
I have two Vivitar M42 teleconverters, a 2X and a 3X. (I think I must be one of the 4 or 5 people who bought the 3X unit!) The 3X has a rotating ring that does the f-number conversion for you. If anyone wants either of these priceless gems, send me a PM. They're yours for the shipping cost.
5 Days Ago   #13
Pentaxian




Join Date: Jun 2008
Location: Idaho
Photos: Gallery
Posts: 1,002
Teleconverters vary a lot. As mentioned, low quality ones aren't worth the effort, but high quality ones can work fairly well. If the main lens isn't too good, its deficiencies are magnified by the teleconverter and you get poor results. Bottom line: use a good teleconverter and lens if possible and even then, cropping might give better results (with cropping you lose total pixel count which you don't with a teleconverter so it pays to compare).
4 Days Ago   #14
Loyal Site Supporter
Loyal Site Supporter
UncleVanya's Avatar

Join Date: Jul 2014
Photos: Gallery | Albums
Posts: 16,665
QuoteOriginally posted by Bob 256 Quote
Teleconverters vary a lot. As mentioned, low quality ones aren't worth the effort, but high quality ones can work fairly well. If the main lens isn't too good, its deficiencies are magnified by the teleconverter and you get poor results. Bottom line: use a good teleconverter and lens if possible and even then, cropping might give better results (with cropping you lose total pixel count which you don't with a teleconverter so it pays to compare).

Well said. The initial lens resolution has to be high and the TC must be very good to exceed the detail from cropping, but it can be satisfactory in these circumstances.
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, converter, pentax help, photography, troubleshooting
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
For Sale - Sold: Sigma APO Tele Converter 1.4x DG EX AF sergysergy Sold Items 13 05-30-2020 08:03 AM
Nature Its amazing what a 2x tele-converter can do...... joelbolden Post Your Photos! 2 10-02-2019 07:18 PM
Best lens aperture (best sharpness) with a tele-converter? palikrovol Pentax SLR Lens Discussion 24 03-02-2019 02:38 PM
For Sale - Sold: Pentax DA 1.4x AW AF Rear tele-converter new lower price - ($349) Lou Kraus Sold Items 8 07-08-2018 04:05 AM



All times are GMT -7. The time now is 04:25 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