Tele-extender or cropping?

Started 11 months ago | Discussions
athleticpete
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Tele-extender or cropping?
11 months ago

I have a teleplus 2x extender which I have used occassionally with mixed results on a Canon 40D and 70-300 zoom. I don't like fact that AF does not work or is extrememly slow so therefore it is only used in extreme circumstance.

I have just treated myself to a Sigma 120-300 f 2.8 zoom so thought I would give the extender another try. The AF works reasonably well and I can manually focus if necessary but now I can really notice the difference with and without the extender. Without the extender at full 300mm zoom pictures are pin sharp, but with the extender, even at 150mm there is a definite loss of quality.

An example without the extender at 1/2000s focal length 250mm

Since I am also considering upgrading my body to a 7D I wonder if, with the increased pixels of the 7D, would I get better picture with a 2x digital zoom in photoshop, rather than the 2x optical zoom on camera. i am sure it would work for small prints, but what about A· size, or larger.

Any thoughts

TIA

Pete

valenciabioparc.wordpress.com

athleticpete
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Re: Tele-extender or cropping?
In reply to athleticpete, 11 months ago

Here's one using the tele-extender, 1/160s at 300m x2.

Admittedly this is at the full range of the lens but it is the best I managed among several using AF and manual. Whilst this is an OK shot it has nothing like the detail of the Eagle.

Am I expecting too much?

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steephill
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Handholding?
In reply to athleticpete, 11 months ago

1/160th sec handheld at 600mm focal length is pushing your luck a bit too far. Tripod mounted you lose camera shake but the shutter speed might still be too low to avoid subject movement.

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StevenMajor
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Re: Tele-extender or cropping?
In reply to athleticpete, 11 months ago

You should  test your equipment to learn what works best.

Since your concern is about sharpness, shoot the same static, detailed composition with and without the converter ( a flat brick wall works well  parallel to the cameras sensor). Use a tripod and only change the shutter speed when using the converter. Treat both image files the same in post processing. Do a 2X crop on the non converter image. Judge both files side by side in Photoshop and you will have your answer.

Since you have a zoom, you can also do the same test at different focal lengths if you wish and you will likely see that results will differ.

What affects image sharpness is camera movement, subject movement, and lens quality. That is why you should use a tripod (correctly) and shoot a static subject for your test..so the results will be affected only by the lens.

That's the long answer...the short answer is to throw out that low end piece of junk converter.

Good Luck

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Henry Falkner
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Re: Tele-extender or cropping?
In reply to athleticpete, 11 months ago

With a tele-converter, the minimum distance at which the camera focusses is further away.

My Olympus SP-570UZ (which does have an adaptor for the Olympus B-300, later renamed the Tcon17) this is particularly noticeable when I try to get small birds.

My Olympus SZ-30MR (for which I had to bodge an old adaptor), works beautyfully with the Olympus B-300.

This particular converter is also tried with other brands of camera. I have read reports saying that the B-300 focus distance with some cameras is wrong, and that adaptors have to be modified to correct this.

I have also found that dust settling on the tele-extender during long periods of storage also misleads the focussing, and the B-300 in particular is prone for the butter finger treatment since it has a large exposed glass surface.

Historically, the B-300 was designed for a 35mm all-in-one SLR, the Olympus IS-3000. Olympus used to state categorically that the B-300 would NOT work with their digital cameras, but I have used it directly with the Olympus C-1400L and the C-2500L at that particular time.

Other tele-extenders may have a similar history.

Henry

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BertIverson
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Re: Tele-extender or cropping?
In reply to athleticpete, 11 months ago

athleticpete wrote:

... Since I am also considering upgrading my body to a 7D I wonder if, with the increased pixels of the 7D, would I get better picture with a 2x digital zoom in photoshop, rather than the 2x optical zoom on camera. i am sure it would work for small prints, but what about A· size, or larger.

Any thoughts

TIA

Pete

A couple of years ago (on a 12MP DSLR), I did some tests to compare digital zoom with 2x tele-extender. I convinced myself to forget the tele-extender. Today with 20-36MP cameras, 2x digital zoom makes even more sense to me. Nothing to carry and no lens fiddling. Maybe in the 1-3MP camera era the optical extenders made sense.
of course, just my experience and personal preference,
Bert

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joejack951
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Re: Tele-extender or cropping?
In reply to athleticpete, 11 months ago

Not all teleconverters are created equal, especially when it comes to 2X converters. If you aren't using the latest Sigma DG 2X teleconverter, you may be selling that option short.

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athleticpete
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Re: Tele-extender or cropping?
In reply to StevenMajor, 11 months ago

StevenMajor wrote:

That's the long answer...the short answer is to throw out that low end piece of junk converter.

Good Luck

Thanks for the honesty Steve. It was bought when I first started and couldn't afford much more. In all honest I generally can't be bothered with fiddling about, especially as the results aren't that good.

www.valenciabioparc.wordpress.com

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athleticpete
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Re: Tele-extender or cropping?
In reply to athleticpete, 11 months ago

Thanks to everyone for taking the time to reply. I think I will try the scientific approach by taking the same shot with the same settings on a tripod just to see if it is worth persevering.

www.valenciabioparc.wordpress.com

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fishywisht
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Re: Tele-extender or cropping?
In reply to athleticpete, 11 months ago

Digital zooms have always been called bad, even if an optical zoom can also be quite bad.

As someone who has had to crop images more often than he'd like, I'd counsel you to beware of the increase in image noise with cropped pictures. At a low ISO you could crop and get something pleasant for web viewing, but it's not the solution of quality.

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(Of course, you could argue the toss just to please yourself)

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Doug Haag
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Re: Tele-extender or cropping?
In reply to StevenMajor, 11 months ago

StevenMajor wrote:

You should test your equipment to learn what works best.

Since your concern is about sharpness, shoot the same static, detailed composition with and without the converter ( a flat brick wall works well parallel to the cameras sensor). Use a tripod and only change the shutter speed when using the converter. Treat both image files the same in post processing. Do a 2X crop on the non converter image. Judge both files side by side in Photoshop and you will have your answer.

Several years ago I did precisely this test with a Nikon 70-300 and a Tamron 1.4 converter ordered from B&H.  Because my 90mm f2.8 Tamron lens is sharper than any of my three Nikon lenses, I assumed it would be good glass.

Immediately following the test, I returned the converter because a crop of the same portion of the image taken without the converter was noticeably better than the same view with the converter.

And, yes, the camera was on a tripod and I held the f-stop constant (adjusting only the shutter speed) so that the f-stop would be the same.

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The Sage Knows
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Crop - but with a sharp original
In reply to BertIverson, 11 months ago

BertIverson wrote:

athleticpete wrote:

... Since I am also considering upgrading my body to a 7D I wonder if, with the increased pixels of the 7D, would I get better picture with a 2x digital zoom in photoshop, rather than the 2x optical zoom on camera. i am sure it would work for small prints, but what about A· size, or larger.

Any thoughts

TIA

Pete

A couple of years ago (on a 12MP DSLR), I did some tests to compare digital zoom with 2x tele-extender. I convinced myself to forget the tele-extender. Today with 20-36MP cameras, 2x digital zoom makes even more sense to me. Nothing to carry and no lens fiddling. Maybe in the 1-3MP camera era the optical extenders made sense.
of course, just my experience and personal preference,
Bert

With enough megapixels (that's why I get much more than I think I'll need for enlargements) and as long you start with a sharp - both optically and without motion blur - original, a crop of up to about 2x will look as good or better than an original with a converter. That is because you will be using the sharpest part of the lens image (cropping out the corners) yet still retaining enough pixels to print an 8x10ish enlargement and more than enough for web.

See also this thread where the subject of cropping was "discussed" (for the most part) :

http://www.dpreview.com/forums/post/52240780

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Robert

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