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02-17-2012, 08:45 AM   #76
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QuoteOriginally posted by newarts Quote
Has anyone posted an example or link to an example where a photo with tc is better than the cropped and enlarged photo taken with no tc but same camera & lens?
The unfortunate reality is that real world shots are never taken with and without the TC so a 1:1 comparison is really tough It would almost be easier to do this with 2 members of a local club who both own the same body and lens. But even then, arguments over variations between lenses, and / or shooting technique and motion blurr would still be around.

For me, the real question is, can you produce high quality shots when using a Tele converter, and the answer is yes, and I have posted many examples from both my sigma APO 70-200/2.8, using sigma's 1.4x and 2x APO teleconverters, and also with my K300/4 using the SMC-F 1.7x AF TC. Better or worse than without the TC, I don;t honestly know, other than I am happy with the results both visible on screen and when printed at sizes up to 11 x 17.

For me, a TC is a very useful tool, because no matter how big a lens, when looking at small birds (some only 2-3 inches long) the image is NEVER big enough.

Lets not forget this, I shoot (or try to shoot) birds. Although I am no where near the level of birding in the current movie "the big year" , I try to photograph every new species I see. I have 2 levels of photo, one being proof of sighting, which only really requires an image of about 150 x 100 pixels, depending on species, and the other is print quality of at least life size.

Lets assume, life size is at 300 DPI and the bird fills about 1/2 the frame.
A 3 inch bird therefore would be filling1/2 a frame at 1800 x 1200 pixels

As a result this needs a minimum of about 2.24 MP

If you can resolve the necessary detail out of roughly 1/6 of a K5 frame, or 1/4 of a K10 frame then a crop may be the best, but lets look at this another way too.

Image size = subject size x focal length / distance.

for my 3 inch bird, lets assume this is 72mm (it will be obvious why in a minute)
the sensor is 24 x 36 mm (both divide evenly into 72mm)
if I use my 70-200 without a TC to fill 1/2 of a 1/6 crop of the K5 frame, I need to be withinn 4.8 meters of the subject.

That might not be possible.

with a 2x i only need to be about 10 meters away for the same shot.

02-17-2012, 10:02 AM   #77
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QuoteOriginally posted by Lowell Goudge Quote
For me, the real question is, can you produce high quality shots when using a Tele converter, and the answer is yes, . . .

We keep this up an' we're gonna need a new bumper sticker and a PF signature block - "I'm a TC user an' proud of it!" - for all those that've finally crept out of the closet with TC in hand.

H2
02-17-2012, 10:51 AM   #78
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QuoteOriginally posted by pacerr Quote
We keep this up an' we're gonna need a new bumper sticker and a PF signature block - "I'm a TC user an' proud of it!" - for all those that've finally crept out of the closet with TC in hand.
How about: I WENT TO eBAY AND ALL I GOT WAS THIS LOUSY TC

Or: US TC USERS WOULD RATHER MOUNT THAN CROP

Maybe: TC OR NOT TC? THAT BE THE QUESTION

Hay, I like this: TCs ARE FOR THE BIRDS
02-17-2012, 12:32 PM   #79
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QuoteOriginally posted by newarts Quote
Here's a test I just did with my equipment. About the only time I'd use a TC is when I can't get close enough to use my DA 55-300 cranked all the way out and wide open so that's what I tested. With my Kenko 1.5x on the 55-300 @ 300:5.8 autofocus still works even though the actual f-stop is about f:8.7. I see no big difference between the photos. (Cropping was the only processing done with Picasa on jpeg output)
Sharpness is similar, but contrast, color depth, and CA are noticeably worse on the TC image, I'd say.

Definitely true that the amount of resolution you have, and the exent to which the lens can take advantage of that resolution, plays a big role in the comparison too. My tests were done on a 10MP camera (K200D), which allows me to crop by the same factor as a 1.5TC and still have enough resolution for decent sized prints. I wouldn't at all be surprised if the results didn't come out better for the TC compared to cropping on a 6MP camera, although contrast, color depth, and CA would still generally favor the bare lens.

Another thing to note: even if I want to print big, it's a fallacy to assume that cropping suddenly becomes less desirable. If the shot without TC has more detail than the shot with TC, that is going to remain true no matter how big you blow them up. You just might need to use some fancier upsizing software to avoid the "pixelation" effects.

But despite all this, I still keep my TC, and appreciate the larger viewfinder image if nothing else.

02-17-2012, 12:52 PM   #80
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I recently bought a Tamron "F-system" 2x TC (4 element) on the cheap. I got it thinking of de-glassing it to make an KA-mount extension tube, but first I wanted to test it out as a TC. So I just did some test shots with and without the TC, on both the DA* 200 and the A 400/5.6. Tentative findings:

With the 400, the TC is no better than cropping.
With the 200, the TC does produce higher resolution than cropping, in the center. Edges are pretty bad.
Arguably, the 200+TC is as good or better in the center than the 400 alone. About as sharp, and maybe better in terms of CA. Again, the edges/corners are a different story.

The latter comparison surprised me. (First I did this with both lenses at f/8, then I did another set with the 200 at f/4 to account for the light loss with the TC. The 200+TC was still comparably sharp in the center.) Makes me want to try the Pentax 2x L-converter.
02-17-2012, 03:46 PM   #81
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QuoteOriginally posted by newarts Quote
Has anyone posted an example or link to an example where a photo with tc is better than the cropped and enlarged photo taken with no tc but same camera & lens?
Well, I went home and made a new test today. You judge if it is "fair" or not. Because I did not test the "telephoto application" since seeing in my place (Danish City) is terribly lousy for the present (winter) time being and that degrades any telephoto test.

So I went for the "macro application" and photographed a stamp as shown below. The image uploaded is an 19.1% crop taken with my Tamron Adaptall-2 SP 35-80mm at closest focusing distance.

As adaptall-2.org says: "Amazingly, this lens yields very good macro performance across the entire film plane when used with Tamron's SP 2X tele-converter. "

Next, I took 5 images with very careful focus - using 8X and 10X liveview - and thereafter another 5 with the Tamron F-series 2X Teleconverter at same closest focusing distance excersizing the same care with focus in liveview.

What I present are 2 times 3 sets with and without TC. Images uploaded are actual 100% crops from images with TC and 200% crops from images without TC. Each crop is taken from different pictures randomly chosen.

Now then, which are which? Feel free to evaluate. I have shuffled the crops around and will wait a day or two to reveal which is which.
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Last edited by Stone G.; 02-17-2012 at 04:06 PM.
02-17-2012, 05:09 PM   #82
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QuoteOriginally posted by baro-nite Quote
I recently bought a Tamron "F-system" 2x TC (4 element) on the cheap. I got it thinking of de-glassing it to make an KA-mount extension tube, ......
Before you de-glass: Are you sure it is a 4-element TC? My F-series for PK (the one used in the example above) is a 5 groups/7-element TC.
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02-17-2012, 05:55 PM   #83
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QuoteOriginally posted by Stone G. Quote
Before you de-glass: Are you sure it is a 4-element TC? My F-series for PK (the one used in the example above) is a 5 groups/7-element TC.
Thanks for the heads up. Mine says on the box "4 elements/4 groups" and says on the TC itself "MC4". I think the de-glassing is reversible if I'm careful, but on the other hand after this test I'm not in such a hurry to do this. May hold out for another copy.

02-17-2012, 07:20 PM   #84
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QuoteOriginally posted by Stone G. Quote
Well, I went home and made a new test today. You judge if it is "fair" or not. Because I did not test the "telephoto application" since seeing in my place (Danish City) is terribly lousy for the present (winter) time being and that degrades any telephoto test.

So I went for the "macro application" and photographed a stamp as shown below. The image uploaded is an 19.1% crop taken with my Tamron Adaptall-2 SP 35-80mm at closest focusing distance.

As adaptall-2.org says: "Amazingly, this lens yields very good macro performance across the entire film plane when used with Tamron's SP 2X tele-converter. "

Next, I took 5 images with very careful focus - using 8X and 10X liveview - and thereafter another 5 with the Tamron F-series 2X Teleconverter at same closest focusing distance excersizing the same care with focus in liveview.

What I present are 2 times 3 sets with and without TC. Images uploaded are actual 100% crops from images with TC and 200% crops from images without TC. Each crop is taken from different pictures randomly chosen.

Now then, which are which? Feel free to evaluate. I have shuffled the crops around and will wait a day or two to reveal which is which.
Nice test!



By 200% do you mean that there are 2 display pixels for every sensor pixel? You up-sampled with a factor of two?
02-17-2012, 09:01 PM   #85
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QuoteOriginally posted by baro-nite:
. . . de-glassing is reversible if I'm careful,
Put a small drop of finger nail polish or equivalent, or scratch an index mark, on the thread/barrel seam as a "witness mark" if you think you might ever want to restore the lens. Makes re-assembly and focus calibration much easier.

H2
02-17-2012, 09:05 PM   #86
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QuoteOriginally posted by baro-nite Quote
Thanks for the heads up. Mine says on the box "4 elements/4 groups" and says on the TC itself "MC4". I think the de-glassing is reversible if I'm careful, but on the other hand after this test I'm not in such a hurry to do this. May hold out for another copy.
I'm not sure if this is an M or an A but if its an M, you can get off brand ones very cheap. You might want to consider keeping this one intact if it does turn out to be a good one.
02-18-2012, 08:02 AM   #87
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QuoteOriginally posted by ripit Quote
I'm not sure if this is an M or an A but if its an M, you can get off brand ones very cheap. You might want to consider keeping this one intact if it does turn out to be a good one.
It's KA. (Actually KR and I've already removed the Ricoh pin.) I'm going to keep it as is, and I just found another KR TC for even cheaper that I will de-glass. Different brand, but from the photos it looks like the identical unit.

QuoteOriginally posted by pacerr Quote
Put a small drop of finger nail polish or equivalent, or scratch an index mark, on the thread/barrel seam as a "witness mark" if you think you might ever want to restore the lens. Makes re-assembly and focus calibration much easier.
Thanks for the tip!

Last edited by baro-nite; 02-18-2012 at 09:40 AM.
02-18-2012, 01:43 PM   #88
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QuoteOriginally posted by newarts Quote
Nice test!


A = Bare Lens, B = with Teleconverter?
Your grouping of the various crops was spot on.

But as to which group came from where, well here is the correct answer:





QuoteOriginally posted by newarts Quote

By 200% do you mean that there are 2 display pixels for every sensor pixel? You up-sampled with a factor of two?
The crops from the images taken with TC are 300 X 200 pixels and uploaded "as is" (100%). The crops from the images without TC were from the identical areas on the stamp. These crops were 150 x 100 pixels in size and are resized by a linear factor of two (200% - linear) before upload. So, actually, there are 4 display pixels for each sensor pixel - but that is also what the TC gives: An enlargement by a factor of two in lenght and by a factor of four in area.

Another way of looking at the result is presenting the original 300 X 200 and 150 X100 crops side by side:



The two ways of presentation are of course equivalent and none show more or less detail than the other.
02-18-2012, 05:40 PM   #89
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TC discussions are going on and off regularly on both Pentax forums for years.
I use exclusively the best of 1.4X TCs with the best long telephoto optics available because I have no choice. I do not go for longer and more intrusive TCs. I don't use old cheap junk. It may work OK, but I demand more by default. I don't expect any miracles when cheap 1.4X-2X TC is paired with something on the cheap side, like DAL 55-300 or so. And I don't even bother to test them trying to squeeze impossible from it. I wouldn't use TC with something shorter than extreme tele photo lenses. I simply avoid attaching of my best 1.4X to the Tamron 28-75/2.8 or DA 16-45/4 to get more reach. I would use DA*60-250/4 instead. I always use a stand alone known good lenses for such situations, covering everything from 10mm up to 300mm.
Beyond 300mm Pentax had suffered for a long time. To me TC is a last resort. I wouldn't bother using them, if I had 400-500mm high quality not too heavy solutions. For now I use FA*300/4.5+Tamron 1.4X Pz-AF combo exclusively, because I don't see anything noticeably better around. And I have chosen my Tamron over five other 1.4x's: I bought them, tried them, and made my final choice. It's a very practical trade off for now.
The Pentax roadmap has been revealed. And it is a breath of fresh air for me and for all of us. If coming 560/5.6's IQ is on par or better than my 300x1.4 combo, I'll buy it in a heart beat. If announced 135-400 zoom is capable of what Sigma 100-300 EX DG or DA*60-250/4 deliver, I'm also in. Then I'will gladly forget about these TC driven discussions for a few months in the raw to start it over after next 3-5 months .
02-19-2012, 05:18 AM   #90
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A "real-life" test

Same equipment used as in my previous thread:

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/175362-telecon...ml#post1831613

But this time, I have made some handheld shots in Manual Mode (with all the extra uncertainties that this will involve). Images to the left are the full, un-cropped frames without and with TC. Images to the right are 200% and 100% crops.

Focus has been determined by Catch-in-Focus and the built in flash was used for these shots.

By and large I think this confirms that each and every TC may not be that bad with all lenses and in all situations after all. One might also note that if I were to use extension tubes, I would have had to get much closer and couldn't have used the built-in flash.
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