Jan 30, 2015

What is a Teleconverter?

I recently shared a photo on our Instagram account of my new teleconverter. Questions were asked and even more questions came in through messages and emails.  So I thought I would share a little bit about it, in case you were wondering yourself.

I bought a 2x teleconverter. There is also a 1.4x teleconverter.  As you can guess the 2x doubles the focal length and the 1.4x adds 40% to the focal length.  I went with the Tamron SP AF 2x teleconverter. Canon, Nikon, and other third party lens companies make them, too.  Since I own a few Tamron SP lenses (their professional quality line), it seemed only natural to match up my teleconverter with my lenses. You can easily use a Canon on a Tamron lens, or a Tamron on a Canon lens.


Image from Tamron’s website

So a little bit about the teleconverter. I have already told you that it doubles the focal length, but you should know it also doubles the aperture you are capable of. So if you want to use it on your 70-200 f/2.8 lens, it can become a 140-400 lens at f/5.6. I have heard many women say that has been a deal breaker for them in the past because they don’t like losing the f-stops. I can understand that.

Sigma and Tamron both have a lens that is 150-600mm. They both start at f/5.6. They are high quality lenses and very sought after for wildlife photographers, so they aren’t the equivalent of a kit lens at all.  Canon’s 100-400mm or even its 400mm is an f/4.  So you aren’t going to find a “fast lens” at these focal lengths on the market.

Without getting into the specifics of math of depth of field, I do want to tell you that bokeh and compression of a shot at 400mm and f/5.6 can still be amazing. It is all about how you position your subject in the setting, just like any other shot. The greater distance between your subject and the background, the better blur. The greater distance between you and your subject, the better background blur. 

Here is an example:


This is one of my kid’s banks. Yes, it is an armadillo. I am a {misplaced} Texan and my family sends Texas stuff to my kids all of the time. ;) So I placed this bank on my fence to take a photo. I am standing 15 feet away form it.  The trees in the background are 20 feet away.  This was shot with my Tamron 70-200 lens.  Settings are: 200mm, f/2.8, 1/160, ISO 320.  This shot has not been cropped or edited. I shot it in RAW and then converted to jpeg and saved as a web optimized image in Photoshop. That is it.


Here is the same bank in the same spot. I did not take a single step. I simply added the teleconverter onto the camera and attached the lens. The settings for this shot are: 400mm, f/5.6, 1/160, ISO 1250. Once again no cropping, no editing. I simply converted from RAW to web optimized jpeg in Photoshop.

As you can see from the settings, I had to bump up my ISO to get the same exposure because of the loss of f-stops. But you can also see how much closer I was able to get without even moving. My max zoom capability of 200mm was now 400mm.  I think the bokeh/background blur is fantastic. So the added f-stop was not as affected because of the added zoom created the same effect.

Teleconverters do have autofocus, but to be able to utilize the autofocus feature you have to be within certain guidelines. The focal length needs to be 90mm or longer.  The lens needs an f-stop of f/2.8 or lower. So you can definitely add a teleconverter to a 100-400mm f/4 lens, but you will be using manual focus. Many, many photographers choose this to get that increased focal length.

You can add a teleconverter to your macro lens.  I have taken the last four Mystery Macro Monday shots with my telecovnerter added to my Tamron 90mm f/2.8 lens.  With that increase in focal length you can get a closer shot without having to be closer.  I was able to capture this snowflake before it melted with my 90mm with teleconverter (making it a 180mm). I shot it at f/5.6 and was so close to it that the entire snowflake barely made it into the depth of field. The snowflake was about 1.5mm. It could have fit on the head of a pin.


If you have any questions about a telelconverter, please feel free to ask. I am by no means an expert, but I will do my best to help. If you have been thinking about getting one, but not sure about it, why don’t you rent one for the weekend and see if it fits your needs. I bought my 2x telelconverter new from a reputable store for $250.  There are less expensive ones on the market and by Tamron, but I chose to get the SP one because I knew I wanted the top of the line glass with it.