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Occasional Contributor
Posts: 6
Registered: ‎03-31-2017

Eos rebel xti

I have xti with EF 75-300mm lens. Looking to get more "zoom" will a teleconverter work with my camera/lens combo? If so please recommend one for me. Or is there another way to accomplish this without spending 1000's of $$? Wildlife/birding photography
Honored Contributor
Posts: 5,038
Registered: ‎08-13-2015

Re: Eos rebel xti

[ Edited ]

Elev8or12 wrote:
I have xti with EF 75-300mm lens. Looking to get more "zoom" will a teleconverter work with my camera/lens combo? If so please recommend one for me. Or is there another way to accomplish this without spending 1000's of $$? Wildlife/birding photography

Very few things in life are "win-win", and this is most especially true of teleconverters.  You pay a heavy price when you use a teleconverter, or extender as they are sometimes called.  Have you researched them, at all?  The price you pay is a reduction in the effective maximum aperture of the lens you're using with the extender.

 

The most common types of extenders multiply the focal length by 1.4, or by 2.  Let's say you have a 100mm f/4 lens.  If you use a 1.4x extender, then your effective focal length becomes, 1.4 x 100mm = 140mm.  But, the price that you pay is that a 1.4x extender reduces the effective maximum aperture by one full stop.  Your 100mm f/4 lens has now become a 140mm f/5.6 lens.

 

With a 2x extender, your maximum aperture is reduced by two full stops.  Your 100mm f/4 lens will become a 200mm f/8 lens.  And, with this narrow of effective maximum aperture, f/8, is where you will get into deep trouble and pay a heavy price.  The AF points in DSLRs are affected by the maximum aperture of the lens being used.

 

A wide aperture allows a lot light to enter the camera, which allows the AF system to focus better than if a narrow aperture lens were used.  But, using an extender reduces the effective maximum aperture of the lens you're using.  You can quickly reach a point where the effective maximum aperture is not allowing enough light to enter the camera for the AF system to properly function.  

 

With most Canon DSLRs, the minimum aperture cutoff point is f/5.6.  A maximum aperture of only f/8 is too narrow for the AF system to work properly.  If you use an extender, you will almost certainly lose the ability to autofocus with the lens throughout most of its' zoom focal length range.  

 

Not only that, not only will you most likely lose the ability to autofocus, the image quality of the lens will most likely take a serious hit, too.  You will most likely get better looking images by using the lens without an extender, and cropping the photos in post-processing.  

 

If you do not think the images from the 75-300mm lens don't look very good when you crop them, an extender will not miraculously improve the IQ of your photos.  Most of the 75-300mm lenses that Canon included in their Rebel camera kits were not their best lens offerings.  An extender will only serve to magnify the existing flaws in the lens, not to mention introducing a few flaws of its' own.  

 

Canon has a couple of holes in its' lens lineup, which they may or may not close.  One glaring hole has been the lack of an affordable zoom lens that goes from medium telephoto to super-telephoto.  One popular type of zoom in this category ranges for about 100 to 150mm on the short end, to about 500 to 600mm on the long end.

 

Canon's only offering in this category is an "L" series lens that ranges from 100-400mm.  It has a list price above $2000.  Canon is being beaten badly by third party lenses that have a longer rated focal length at the long end, 500-600mm, and sell for more or less half the price of the Canon "L" series lens.

 

Rumor has it that Canon is working to release a lens to compete with third party 150-600mm lenses.  I have high expectations for such a lens from Canon.  Rumor says it may be released within the next year or two.  Maybe as soon as this summer or fall.  If so, this lens is probably what you're looking, instead of an extender.

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Honored Contributor
Posts: 7,919
Registered: ‎12-07-2012

Re: Eos rebel xti

"...will a teleconverter work with my camera/lens combo?"

 

The simple answer is, no, it will not.  The cheapest and actually pretty good lens for little money is the Bower 500mm f/8 Manual Focus Telephoto.  It is completely manual. One reason why it is so inexpensive at about $120 bucks.  This lens is a branded lens and sold by several names but it is the same lens.

 

Over the years I have had several of these.  I have one now!  They used to make a 400mm f6.3 version that was really a nice lens. Better than it should be. You may be able to find a used one.  It should cost around $30 bucks on the used market.

 

Now if you are so inclined to get the best in IQ for a 400mm lens, the Canon EF 400mm f/5.6L USM Lens is it.  They run around $1200. This lens has no peers.  Nobody makes a lens like this one.  I have seen them for $700 to $900 on the used market.  Hey, you did say, "...way to accomplish this without spending 1000's of $$"  It's not 1000's !  The Canon 400mil is a must have for every photographer.  I have two of them and both are simply fantastic.  Completely handholdable, too, for BIF.

A lot of Canon stuff. Along with, a lot of other stuff.
Occasional Contributor
Posts: 6
Registered: ‎03-31-2017

Re: Eos rebel xti

Thanks for the advice. Sounds like I'm gonna have to bite the bullet and buy a larger lens. I may give that Bower lens a try and work on my manual focusing.
Honored Contributor
Posts: 5,038
Registered: ‎08-13-2015

Re: Eos rebel xti

[ Edited ]

Elev8or12 wrote:
Thanks for the advice. Sounds like I'm gonna have to bite the bullet and buy a larger lens. I may give that Bower lens a try and work on my manual focusing.

Depending upon the type of birding you're looking to do, I would pass on the manual only Bower lens, and other similar lenses.  If you want to photograph fast action, like birds in flight, then save up your money and buy an automatic focusing, super telephoto lens. 

 

Sigma has recently announced a fairly reasonably priced 100-400mm lens, but it hasn't hit the stores, yet.  Another popular birding lens from Sigma is the 150-600mm "Contemporary", and its' big brother the 150-600mm "Sport". 

 

For birding, you can never have too much focal length.  For action shots, you probably want at least 500-600mm.  For capturing still shots of rare birds sitting trees, then a manual focus, super telephoto lens and a good tripod could work out fairly well. 

 

I live nearby to a National Audobon Society Bird Sanctuary.  They hold annual events for birders.  Many people are out there digiscoping with spotting scopes.  They're getting magnifications of 20-60x.  How much focal length is that? 

 

To calculate the magnification factor, divide the focal length of a lens by 50mm, which is considered to be a "normal" lens that approximates what the human eye sees.  A magnification of 20x would equivalent to a 1000mm lens, a 60x magnification would be equivalent to 3000mm. 

 

You will need a VERY ROBUST tripod and mount with those magnifications, though.  The smallest vibrations will cause the image to jump around the frame.  Even the vibrations of the mirror moving up and out of the way blur a shot.

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"I don't rent software. I use Photoshop CS6, ACR 9.8 and Lightroom 6.8 ."
Occasional Contributor
Posts: 6
Registered: ‎03-31-2017

Re: Eos rebel xti

Thank you for your wealth of knowledge. I will keep an eye out for those sigma lenses on eBay or the local pawn shop. I figure if I can get the bower lense for around $30 or so that should keep me busy for a while as I save for the larger lens. I realize it will only be still shots but should work for birds at the feeder or waterfowl floating along. Thanks again. At least now I have a clue what to look for.
Honored Contributor
Posts: 7,919
Registered: ‎12-07-2012

Re: Eos rebel xti

Elev8or12,

I am not pushing the Bower 500mm f/8 Manual Focus Telephoto or any of these very low cost lenses.  I only mentioned it because you seemed to want that price range.  However, it isn't as difficult to use as it may seem.  Don't rely simply on posts especially from people that don't own and use the gear.  These lenses are respectable for what they are.  They are not high quality Canon "L" glass.  At one time we shot everything with a fully manual lens.  Guess what?  We did very well thank you.  YOU CAN TOO!

 

One nice thing is as your distance increases and your aperture decreases your DOF increases.  Example, with the Bower 500mm f/8 Manual Focus Telephoto set wide open @ f8 and 40 ft from a bird, you can miss focus by approx, 6 inches and still have acceptable IQ.  f11 and you get around 9 inches.  Of course it is best to get spot on but it is nice to have a small leeway.  Right?

 

When you have the coin saved up, you need to seriously consider the Canon EF 400mm f/5.6L USM Lens.  I can not put enough positive accolades on this unique lens.  It is legendary in the photographic world. Another lens I can not praise enough is the Canon EF 300mm f/4L IS USM Lens. It is a little more expensive but for that you get IS and the ability to use the EF 1.4x tele converter.  WIth it installed the 300mil f4 becomes a 420mil f5.6 with IS.  WIn, win !  There are very few lenses I ever use a converter on but the  Canon EF 300mm f/4L IS USM Lens is one of them.  It is even better IQ than the fantastic EF 400mm f/5.6L USM Lens. The 300mil can afford the slight loss of IQ caused by the converter.  Most lenses can't.

 

So there you are get the Bower and start shooting and start saving.  That EF 400mm f/5.6L USM Lens is calling you, I can hear it clear over here on my side of the monitor.

A lot of Canon stuff. Along with, a lot of other stuff.
Honored Contributor
Posts: 5,038
Registered: ‎08-13-2015

Re: Eos rebel xti

[ Edited ]

One doesn't need to own a Bower 500mm f/8 lens to know that it would not be good for birding with today's DSLRs.  Some people forget that the camera body is also part of the photography process.

 

It's true that manual focus lenses were used for decades before the advent of autofocusing lenses and camera bodies.  Your camera body is designed for autofocus lenses.  Your camera lacks the manual focusing aids that were found in the viewfinders of the old cameras.  

 

A manual only lens would be not be as easy to use as some people want you to believe.  In fact, it would be tricky, at best.

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"I don't rent software. I use Photoshop CS6, ACR 9.8 and Lightroom 6.8 ."
Occasional Contributor
Posts: 6
Registered: ‎03-31-2017

Re: Eos rebel xti

Haha. Thanks again. You have been a great help. I'm not looking to publish pictures in National Geographic so not sure that I need top of the line equipment if I can save a few bucks and get the sigma lens you mentioned without sacrificing too much quality. If you don't mind me asking one more question... I bought this camera at a pawn shop about 7 years ago for $200. Came with cannon 18-55mm lens and 75-300 mm lens. I haven't used it much. Basically I moved and it ended up in storage and I forgot about it. Any way the 75-300 EF lens has a sunpak 58mm circular polarizer on it that I just figured out is removable. What is the purpose of the polarizer and when should/shouldn't I use it?
Honored Contributor
Posts: 5,038
Registered: ‎08-13-2015

Re: Eos rebel xti


Elev8or12 wrote:
Haha. Thanks again. You have been a great help. I'm not looking to publish pictures in National Geographic so not sure that I need top of the line equipment if I can save a few bucks and get the sigma lens you mentioned without sacrificing too much quality. If you don't mind me asking one more question... I bought this camera at a pawn shop about 7 years ago for $200. Came with cannon 18-55mm lens and 75-300 mm lens. I haven't used it much. Basically I moved and it ended up in storage and I forgot about it. Any way the 75-300 EF lens has a sunpak 58mm circular polarizer on it that I just figured out is removable. What is the purpose of the polarizer and when should/shouldn't I use it?

In order to fully understand what a polarizer does requires a couple of physics lessons about light.  Suffice to say that a CP filter is basically like giving your camera a pair of sunglasses.  It helps to reduce the glare from reflected sources, particular the sky and light reflections off of water.

 

A CP filter works by aligning light waves along one plane.  Normally light waves move in all directions.  Have you ever seen someone grab the end of a long rope, or garden hose, stretched out across the ground, and then grab one end of it so that a "wave" travels the length of it, or until it runs out of energy.  That is one way how light can travel.

 

The wave in the rope is aligned vertically.  Light waves move the same way, but not just vertically.  Their waves can move up and down like the rope, or side to side like a snake in the grass, and all of the angles in between horizontal and vertical.  What a CP filter does is allow light to pass through that is only aligned in one direction.

 

You move noticed that the glass element of the CP filter can rotate independently of the mounting threads, which attach it to the front of the lens.  This allows you to select the angle of polarization that you want.  Of course, you cannot see the light waves light you can on the garden hose example, but what you can see is a reduction in the intensity of the glare as you rotate the CP filter element.

 

One very good way to see this filtering in action, is to look through the camera's viewfinder at a flat screen TV.  If the flat screen is an LED TV, you will see the image on the TV screen fade in and out as you rotate the CP filter.  In fact, you should be able to find a sweet spot where the TV screen is completely blanked out!

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"I don't rent software. I use Photoshop CS6, ACR 9.8 and Lightroom 6.8 ."
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