Teleconverter and purple haze question...

Joemess · January 23, 2007

Hey folks, I picked up a teleconverter on a whim a while back and took it to the local wetland to play with it. I have to say i was disappointed in my efforts. Anytime I took a photo of a white bird, say a great egret, I would get this funky purple halo around the white portion of the photos. I would love to post an example, but I believe I deleted the files in disgust.... (this was before I found this outlet to ask questions)

I was shooting in bright sunlight, a 2X teleconverter on a Quantaray 70-300mm 1:4-5.6 LD The camera was a 300D. I have started buying canon glass, but I was on a budget for a while.

Now, I am the proud owner of a 30D and have yet to really get a chance to fire it up and do any shooting, but when I do if I choose to use this doohicky are there any tips and or prior knowledge I should know about? Or should I just relegate it to the back of the drawer as a gimmick?

But again, the main question was what about the lens structure makes the purple phase flare around the white.

Andrew

cmason · January 23, 2007

I hope you attempted to clean up the shots in your photo editting software, as you can make big improvements on purple fringes with software, so I suggest you try cleaning up the photos first.

But, a teleconverter does bring challenges, and frankly degrades images in one way or another with any lens, including some of the best (and most expensive) lenses out there. That being said, the quality you get greatly depends on the quality of the lens itself. An extender will exagerate flaws in a lens, plus add some of its own. You haven't said what brand you 2x is, but in general you need a brand name, with good glass. Also, the more 'extending' you do, the more exagerated the degradation. Finally, 2x are known to impact autofocus for most cameras, your Rebel being one, and this could be adding to the problem (not sure)

But, I would have to say that your Quantaray lens would be my first suspect. It is not known as a high quality lens, and perhaps exhibits purple fringing on its own, only exacerbated by the 2x extender.

Search the forums and you will see photos taken with extenders that are remarkable, but typically I would say these are done with 1.4x extenders (typically Canon, Kenko or Sigma) and usually the higher end lens, such as Canon L or a Sigma EX lens.

In the end, it really comes down to a combination of lens and extender that works for you. Some lenses seem to work better with them, others not. It seems that this combination does not work for you, so you may wish to try a different extender, or try your extender on a new lens. This could be a criteria for a new lens, finding one that works for you with your extender...

Joemess · January 23, 2007

Thanks for the reply...
The brand of the teleconverter is Quantaray as well... I have to say that I did not try to clean up the images, there was just to much flare for me to want to really even mess with them. To be honest, the teleconverter was bought on a whim... Most of my shots are of a botanical nature, I just wanted a cheap alternative to a big telephoto lens. I think that is what I got...

Anyway, I think I am going to focus on the use of just a lens / camera combo without the teleconverter. but if anyone has any words of wisdom I will be glad to take it all in.

Andrew

sirsloop · January 23, 2007

That lens plus a teleconverter spells trouble. TCs reduce image quality on ALL lenses they magnify, so when you start out with a real entry level zoom lens like that 70-300, then add an entry level 2x converter, you don't get very good results. In reality, the only lenses that really fair all that well with a 2x TC are the big canon f/2.8-f/4 superlong primes. You'll lose AF as well with any f/4 lens or smaller and a 2x TC.

My guess is that 70-300 already had poor CA performance, and the addition of a 2x TC magnified the problem. My opinion... sell the 2x converter and get a 1.4x kenko pro300 TC. Its got great image quality and will fit on any EF (not ef-s!) lens. It will effectively make your 70-300 a 420mm - f/8. If you have the budget for it, get a better lens too!!

That lens in reality is at best a 70-200 f/8 withot the TC... im sure its 300mm f/5.6-f/8 performance is pretty bad.

Canon 70-300IS f/4-f/5.6 + 1.4x kenko on a bright day isnt a bad setup. 420mm f/8... really usable at f/11. I have this lens and have done this on occasion
Canon 70-200 f/4L + 1.4x kenko is a nice 280mm f/5.6 setup
Canon 70-200 f/2.8L + 1.4x kenko is what I shoot with!

Add IS to either of those L lenses for 5-600 bucks

don't fear the 1.4x on a decent zoom lens!

date taken: 2007-01-20 09:56:35
date digitized: 2007-01-20 09:56:35
date modified: 2007-01-20 09:56:35
make: Canon
model: Canon EOS DIGITAL REBEL XTi
size: 3888px x 2592px
file size: 6.58 MB
aperture: f/4.0
iso: 400
focal length: 265mm (guess: 281mm in 35mm) Canon 70-200 f/2.8L + 1.4x
exposure time: 0.0015s (1/640)
flash: flash did not fire, compulsory flash mode
exposure program: aperture priority
exposure bias: 0
exposure mode: 0
white balance: manual
colorspace: sRGB

Joemess · January 23, 2007

sirsloop wrote:

That lens plus a teleconverter spells trouble. TCs reduce image quality on ALL lenses they magnify, so when you start out with a real entry level zoom lens like that 70-300, then add an entry level 2x converter, you don't get very good results. In reality, the only lenses that really fair all that well with a 2x TC are the big canon f/2.8-f/4 superlong primes. You'll lose AF as well with any f/4 lens or smaller and a 2x TC.

My guess is that 70-300 already had poor CA performance, and the addition of a 2x TC magnified the problem. My opinion... sell the 2x converter and get a 1.4x kenko pro300 TC. Its got great image quality and will fit on any EF (not ef-s!) lens. It will effectively make your 70-300 a 420mm - f/8. If you have the budget for it, get a better lens too!! That lens in reality is at best a 70-200 f/8 withot the TC... im sure its 300mm f/5.6-f/8 performance is pretty bad.

Canon 70-300IS f/4-f/5.6 + 1.4x kenko on a bright day isnt a bad setup. 420mm f/8... really usable at f/11. I have this lens and have done this on occasion
Canon 70-200 f/4L + 1.4x kenko is a nice 280mm f/5.6 setup
Canon 70-200 f/2.8L + 1.4x kenko is what I shoot with!

Add IS to either of those L lenses for 5-600 bucks

don't fear the 1.4x on a decent zoom lens!

date taken: 2007-01-20 09:56:35
date digitized: 2007-01-20 09:56:35
date modified: 2007-01-20 09:56:35
make: Canon
model: Canon EOS DIGITAL REBEL XTi
size: 3888px x 2592px
file size: 6.58 MB
aperture: f/4.0
iso: 400
focal length: 265mm (guess: 281mm in 35mm) Canon 70-200 f/2.8L + 1.4x
exposure time: 0.0015s (1/640)
flash: flash did not fire, compulsory flash mode
exposure program: aperture priority
exposure bias: 0
exposure mode: 0
white balance: manual
colorspace: sRGB

Thanks to you as well.... That is pretty much what I was assuming. The lens itself has performed "pretty" well for me if you keep in mind I did not know what I was doing. I agree on the good glass, I just picked up a 100mm 2.8 from canon and I am amazed at the difference. Night and Day. I can only imagine what it is going to do on the 30D.... (if I could find a few minutes to get out of my lab to go play with it)

claudermilk · January 23, 2007

OK, Quantaray superzoom + Quantaray converter. Seems to me there's the problem. Once your budget allows buying some decent glass I would expect much improved results (better glass before the 30D would have been much more bang for the buck).

sirsloop · January 23, 2007

Joemess wrote:

Thanks to you as well.... That is pretty much what I was assuming. The lens itself has performed "pretty" well for me if you keep in mind I did not know what I was doing. I agree on the good glass, I just picked up a 100mm 2.8 from canon and I am amazed at the difference. Night and Day. I can only imagine what it is going to do on the 30D.... (if I could find a few minutes to get out of my lab to go play with it)

Honestly, I wouldnt expect all that big of a difference between the 300D and the 30D. You will see HUGE benefits when you bolt on top notch glass on either body. Instead of getting a 30D I would have gotten at least one or two real nice lenses... maybe a 17-40L and the 70-200/4L. Live and learn I suppose

that 100/2.8 is an excellent place to start though!

Joemess · January 23, 2007

yep

sirsloop wrote:

Honestly, I wouldnt expect all that big of a difference between the 300D and the 30D. You will see HUGE benefits when you bolt on top notch glass on either body. Instead of getting a 30D I would have gotten at least one or two real nice lenses... maybe a 17-40L and the 70-200/4L. Live and learn I suppose

that 100/2.8 is an excellent place to start though!

Well , my the 300D was a graduation present my wife received... When I graduated She said she wanted her camera back.

so I started looking for me a body. I went with the 30D based on a number of factors, not limited to it is just built better and is a little larger (big dude here)

Geeeze, and those folks at Wolf Camera said Quantaray was a good lens

Its all a learning curve.... expensive learning curve though.
Andrew

Phyxius · January 23, 2007

I don't know anything about teleconverters, but I do know about chromatic aberrations, that purple fringe.

Luckily someone posted a link on here for me about a month ago with an AWESOME action by Shay Stephens that is SO simple to use you it just takes 1-2 clicks. And IT WORKS!

Shay Stephen's Chromatic Aberration Action

Best $10 you can spend.

Joemess wrote:

Geeeze, and those folks at Wolf Camera said Quantaray was a good lens

Yeah, they make more money selling you the Quantaray. And, they know you'll be getting rid of it and upgrading shortly after you start using it. Wolf/Ritz is evil that way, but if you're like me they're also the only game in town. (And they offer 10month no interest on purchases over $300 with their card)

sirsloop · January 23, 2007

Joemess wrote:

Geeeze, and those folks at Wolf Camera said Quantaray was a good lens
Andrew

Of course they did!

My 400D plus the battery grip is great for big hands... and I'm no average big guy. I'm 6'9" 255

The 20d and 30d are nice with the battery grip too... i'm not a big fan without cause my pinkey hangs off the bottom of the body.

TylerW · January 23, 2007

Joemess wrote:

Geeeze, and those folks at Wolf Camera said Quantaray was a good lens

Isn't Quantaray the Wolf Camera house brand, and are the Sigma lenses that didn't make the Sigma quality control cut?

gus · January 23, 2007

Joemess wrote:

funky purple halo around the white portion of the photos. I would love to post an example, Andrew

It is called chromatic aberration which is can be typical of a lens shooting into a bright area (we all get it from time to time)...send our very own Shay $10 & all is gone forever.

claudermilk · January 24, 2007

Joemess wrote:

Well , my the 300D was a graduation present my wife received... When I graduated She said she wanted her camera back. so I started looking for me a body. I went with the 30D based on a number of factors, not limited to it is just built better and is a little larger (big dude here)

Geeeze, and those folks at Wolf Camera said Quantaray was a good lens

Its all a learning curve.... expensive learning curve though.
Andrew

OK, the body makes sense now.

Second lesson learned: Wolf/Ritz is evil & overpriced. Never shop there. If there's nothing else local, then B&H, Adorama, KEH, etc. are your friends. For lenses you really want to stick with Canon, Tokina, Sigma, and Tamron; then check up on the 3rd party ones before jumping, some are equivalent or near-equivalent to Canon's, some aren't anywhere near.

erich6 · January 24, 2007

I fell into the Quantarray 70-300 trap when I got my Rebel 300D a few years ago. When it comes to telephoto lenses there's no way around it. If you want good image quality you're going to have to fork out the $$.

That said, now that you have the 70-300 you might as well use it as much as you can until you can afford a better lens. My recommendation is to save and get the top-of-the-line Canon. Meanwhile just practice shooting with your cheapy Quantarray. Focus on learning techniques that will help you take better pictures no matter what quality lens you have. Steady handholding at long focal lengths, using a monopod, etc.

You can actually get some decent pictures with the Quantarray...you just have to know it's limitations. Stressing conditions like the high contrast scene you described will not work.

Here are a couple of examples of what I was able to get with the Quantarray. Not contest winners but decent.

Word of warning...these are never straight out of the camera type of shots. You have to invest some time in post-processing....

Erich

Teleconverter and purple haze question...

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