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08-12-2009, 04:43 AM   #16
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I also believe that sometimes cropping isn't the answer.

I picked up a Teleplus 2x MC4 teleconverter (it has PZ contacts but SDM won't activate and Sigma HSM just hunts - both 2.8 lenses - however my DA16-50 will focus with screw drive through the Converter with my *istD)

Anyway I had this thing mounted on my Sigma 70-200 2.8 HSM II on the weekend and got the sort of results cropping just couldn't achieve.



Fullsize link below (please be gentle on my server)

http://pictures.1337it.com/FullSize/IMGP9220.jpg

Of course I had to MF and Catch in Focus while panning @ 380mm so a lot of shots weren't that good. All those were down to the operator not the gear. In the above shot I nailed it and you can see how well a cheap little MC4 tele did.

08-12-2009, 09:21 AM   #17
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I also don't believe in cropping..period.
I always believe that you have to always frame the shot right the first time..then hope for the best.
Minimal cropping might be recommended 'coz viewfinders don't actually give you 100% of the frame so a slight mis-framing more than likely always happens.
08-12-2009, 09:23 AM   #18
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QuoteOriginally posted by Skyntara Quote
I also believe that sometimes cropping isn't the answer.

I picked up a Teleplus 2x MC4 teleconverter (it has PZ contacts but SDM won't activate and Sigma HSM just hunts - both 2.8 lenses - however my DA16-50 will focus with screw drive through the Converter with my *istD)

Anyway I had this thing mounted on my Sigma 70-200 2.8 HSM II on the weekend and got the sort of results cropping just couldn't achieve.



Fullsize link below (please be gentle on my server)

http://pictures.1337it.com/FullSize/IMGP9220.jpg

Of course I had to MF and Catch in Focus while panning @ 380mm so a lot of shots weren't that good. All those were down to the operator not the gear. In the above shot I nailed it and you can see how well a cheap little MC4 tele did.
Nice shot by the way! The image is always also clearer and cleaner if it is not cropped as all the pixels that are supposed to be there when you took the shot stays there.
08-12-2009, 11:02 AM   #19
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QuoteOriginally posted by GerryL Quote
I also don't believe in cropping..period.
I always believe that you have to always frame the shot right the first time..then hope for the best.
Why? I've met several who feel this way, but I have never understood the logic. If it yields results not possible or as easy to achieve in other ways, why on earth not? You might as well say it's "cheating" to use a zoom lens, or to use AF, or for that matter to use a camera at all instead of whipping out the easel and paints. Unless maybe you built the camera yourself out of a shoebox and ground the lens yourself out of a Coke bottle, using a stone you picked out of the river. I mean really, there's a lot of post-processing that feels like "cheating" in some way, but cropping is at the bottom of that list, it seems to me.

Don't get me wrong; I too take a certain amount of pride in framing well in the first place, and prefer not to crop most of the time. But if the alternative is spending money on a device that is a pain to use and flat out doesn't produce results as good as cropping, I'll give up that bias in an instant. I'd rather have a better picture than be able to brag that I didn't need to crop to get it.

Anyhow, it is true that cropping doesn't *always* produce better results than a TC. It depends on the specific TC, the specific lens, and also whether you can afford the two-stop loss of light. Also how big you intend to print - a heavy crop might be sharp for screen viewing or small prints but look too pixelated in larger ones, while an otherwise inferior uncropped image might look less objectionable in a large print. But in my experience is that in *most* cases, cropping the image without TC will beat using the TC. And images posted to show the alleged benefit of the TC that don't also show the corresponding cropped image without the TC don't really prove otherwise.

I suspect TC's were more advantageous with film, where cropping required more specialized tools and procedures - you had to either produce the prints yourself or pay someone extra to do it for you. With digital, the convenience advantage of the TC is gone, and I'm not sure there ever was much of an IQ advantage.

08-12-2009, 11:31 AM   #20
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QuoteOriginally posted by Marc Sabatella Quote
Anyhow, it is true that cropping doesn't *always* produce better results than a TC. It depends on the specific TC, the specific lens, and also whether you can afford the two-stop loss of light. Also how big you intend to print - a heavy crop might be sharp for screen viewing or small prints but look too pixelated in larger ones, while an otherwise inferior uncropped image might look less objectionable in a large print. But in my experience is that in *most* cases, cropping the image without TC will beat using the TC. And images posted to show the alleged benefit of the TC that don't also show the corresponding cropped image without the TC don't really prove otherwise.
Well said, Marc.

The OP didn't ask about the use of TC in general. He specifically mentioned the use of TC with his Pentax 18-250mm. The lens IQ is already so-so at 250mm, adding a 2X TC will make it worse (besides the fact that AF is not possible). I'm not sure why other posters keep discussing the use of TC in general. Some even cited the use of TC with a Sigma 70-200 2.8 HSM II, a totally different animal.
08-12-2009, 01:38 PM   #21
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QuoteOriginally posted by KyPainter Quote
I have both the Tamron-F AF Tele-converter (2X Pz-AF BBAR MC7) and the Vivitar 2X Macro Focusing Teleconverter with electrical contacts but no AF. I've tried each with a variety of lenses, from modern zooms to old fast primes, and as far as I'm concerned the loss of IQ is too great to justify using them.

The *only* times I've gotten as good or better images by using a 2X teleconverter instead of just cropping or blowing up an image taken without one is when focusing on really distant small objects. I'm fairly certain the only reason for that is the added magnification allowed for more accurate focus, certainly with my eyes, maybe with the autofocus.

Of the two, the Tamron performs more consistently and provides better images. That surprised me based on what many say about the vivitar. Of course the Tamron doesn't help for close focusing and the Vivitar will let you get very close with a 50mm on it.
I did some testing 6 months back using a tripod and focused on a picket fence about 1/2 mile away.
a. I used my Tamron 7 element Pz 1.4TC with a DA*300mm (combination equivalent to 420mm) lens versus an SMC 400mm manual focus lens, both have lens mounts.

b. I took several tries with each lens, bracketing the white picket fence with aperture and shutter settings, within reason.

c. The 1.4 Tamron with DA 300mm was slightly better than the 400mm. The DA 300mm shots that were cropped were 3rd behind the 1.4/300 combo and the 400.

NOTE: The 1.4 TC makes for a gritty feeling when combined with the 18-250, its not dirty, its the feeling of pushing the AF gear train, even when camera is set on MF. I wrote Tamron and they replied that the Tamron 1.4TC was not recommended for the Tamron 18-250. I find i could still autofocus with the 1.4 and the 18-250, in most cases -1 stop loss of light. But often i disliked losing the stop of light so don't use that combo anymore. You can manual focus with the 1.4 in place, it just doesn't have that silky smooth action that one expects of a Pentax manual focus lens.

Don't have any 2x TC so can't comment on that.
08-12-2009, 01:48 PM   #22
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I don't think you will have very good results with any tc and the 18-250. There are some inexpensive long manual lenses that come up regularly for sale. I use a 1.5x kenko and a 1.7x promaster on the tamron 70-200mm and pentax f* 300mm lenses. the results are decent and they do autofocus. but you are talking about $8-900 for such a combo. save your money and get a longer lens. You could sell the 18-250 and pick up a 55-300 and 18-55 (or 17-50mm). that would give you a bit more reach, the same lower coverage and better iq
08-13-2009, 07:49 AM   #23
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I also wouldn't recommend using any teleconverter on the 18-250 lens... it's just too slow throughout its zoom range. Heck, I don't know if I recommend a UV filter on that glass - and I own and like that lens very much. But a 1.4/1.5x or even a 2x converter on something like a 70-200mm f/2.8 lens can be a great package. Very flexible. Very fast when you want/need it and very long when you want/need it. But the key to image quality is to buy a converter that is meant for the lens. Sigma offers a 2x converter that's meant for its 70-200mm f/2.8 HSM lens and the results prove it. Tamron makes an excellent - and less expensive - 70-200mm f/2.8 lens (no HSM). But I can't seem to find any new Tamron 2x converters - especially for Pentax. There's a Kenko converter (a cheap one at $99 and a better one at $149). But I've yet to hear how well this combination works. Teleconverters are fine - but you must start with a fast lens.

08-13-2009, 01:43 PM   #24
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QuoteOriginally posted by philbaum Quote
. I wrote Tamron and they replied that the Tamron 1.4TC was not recommended for the Tamron 18-250. I find i could still autofocus with the 1.4 and the 18-250, in most cases -1 stop loss of light. But often i disliked losing the stop of light so don't use that combo anymore. You can manual focus with the 1.4 in place, it just doesn't have that silky smooth action that one expects of a Pentax manual focus lens.

Don't have any 2x TC so can't comment on that.
I think Tamron gave you a very sensible response: teleconverters are simply not made to be used with slow super-zooms.

Originally tcs were made for specific lenses only (nothing else, but the ancient covertible lenses). Later manufacturers always stated, that they were intended for use with fixed focal length lenses and over a very long period they explicitly stated, not to use tcs with zoom lenses at all.

Then the first dedicated tcs for specific zoom lenses came onto the market (Vivitar was among the first with the matched tc for the 70-210/3.8 if I remember correctly) ans somehow many people simply thought, that now tcs could be used with any lens, prime or zoom, fast or slow. That is wrong.

The tc will multiply not only the focal length by its facor, it will obviously also enlarge all the inherent flaws of the lens by the same factor. Add to that the unavoidable loss of contrast and sharpness, which even a matched tc for a certain lens needs to produce.

So we can easily see, that a mediocre lens (and all super-zooms are nice, but mediocre from a pure iage quality point of view) becomes a very poor lens, when a tc is added - and it is for good reason, that manufactureres do not recommend the use of these lenses with any tc at all. It might be feasible, but then indeed, cropping might be the better choice.

I don't theorize on this topic, I have roughly 10 tcs (among them all the Pentax modells and the two Sigma Apos) at hand and use them only very rarely and with a few select lenses, where their useage makes sense.

Ben
08-13-2009, 01:46 PM   #25
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QuoteOriginally posted by Biro Quote
But a 1.4/1.5x or even a 2x converter on something like a 70-200mm f/2.8 lens can be a great package. Very flexible. Very fast when you want/need it and very long when you want/need it. But the key to image quality is to buy a converter that is meant for the lens. Sigma offers a 2x converter that's meant for its 70-200mm f/2.8 HSM lens and the results prove it. Tamron makes an excellent - and less expensive - 70-200mm f/2.8 lens (no HSM).
That is true. And Sigma emphasizes, that their tcs should only used with certain select lenses, to retain image quality (apart from that, the Sigma tcs cannot be used with too many lenses, due to their protruding front elements). You can easily say, the Sigma Apo tcs are matched to the Sigma 70-200/2.8 - it is one of the best lens+tc-combos available.

Ben
08-14-2009, 06:09 AM   #26
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The flip side to this is that on the day I was shooting, there were heaps of pros with huge white lenses and fullframe setups.

These guys tend to shoot wider and crop down. Shooting wide lets you catch a fast moving target without having to worry as much about framing.

With their 21 Megapixies, I bet they cropped down to a picture the size of mine (or bigger) and got good results on pretty much every shot. I on the other hand had a lot of trouble with fast moving objects that almost fill the whole frame and trying to be steady while hand holding a big, heavy, long lens with no SR on.

So really cropping owned my efforts in this case.

For me personally, all things being equal, I will get better shots with the TC than without. It's all about what works for you and what compromise you're willing to make.
08-14-2009, 08:04 AM   #27
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QuoteOriginally posted by Skyntara Quote
The flip side to this is that on the day I was shooting, there were heaps of pros with huge white lenses and fullframe setups.

These guys tend to shoot wider and crop down. Shooting wide lets you catch a fast moving target without having to worry as much about framing.

With their 21 Megapixies, I bet they cropped down to a picture the size of mine (or bigger) and got good results on pretty much every shot. I on the other hand had a lot of trouble with fast moving objects that almost fill the whole frame and trying to be steady while hand holding a big, heavy, long lens with no SR on.

So really cropping owned my efforts in this case.

For me personally, all things being equal, I will get better shots with the TC than without. It's all about what works for you and what compromise you're willing to make.
Exactly right. And, for many people on these forums, it's also a money issue. They might be able to reach for that $1000 - or even $1200 - lens... but to begin with a $2500-$3000 full-frame camera body and then add quality lenses is simply unrealistic for many. Plus, the size and weight of a full-frame DSLR has to be considered. If one makes a living in photography, then in many cases full frame is the cost of doing business. For the rest of us, there are other options that are quite reasonable.
08-14-2009, 10:26 AM   #28
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QuoteOriginally posted by Biro Quote
Exactly right. And, for many people on these forums, it's also a money issue. They might be able to reach for that $1000 - or even $1200 - lens... but to begin with a $2500-$3000 full-frame camera body and then add quality lenses is simply unrealistic for many. Plus, the size and weight of a full-frame DSLR has to be considered. If one makes a living in photography, then in many cases full frame is the cost of doing business. For the rest of us, there are other options that are quite reasonable.
True, money will be an issue for almost everyone in the forum. I fall into that category and I bought a Pentax K T6 2X rear converter to satify that itch for a longer lens. Sadly, the reslts were less than optimal and the old K T6 2X sits unused on the shelf. I might as well just saved for a year or so and got the longer lens to start with. I find this to be the case nearly every time I try to find an inexpensive option. I'm never satisfied and end wind up spending more in the long run.

Tom G

Last edited by 8540tomg; 08-24-2009 at 11:15 AM. Reason: typo
08-24-2009, 06:33 AM   #29
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hi,

could anyone tell me if the Kenko 2X MC4 is a good teleconverter or not?
Thanks a lot.
08-24-2009, 06:40 AM   #30
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be very careful with SIGMA TCs

I note the OP commented about the sigma 2x TC.

While this is an excellent TC and has produced many fine results posted by myself and other forum members, there are a few cautions.

Sigma TCs require an opening in the rear of the lens 35mmin diameter 10mm deep, because the front element of the TC protrudes into the rear of the lens.

Sigma TCs only work, as a result on a select few lenses typically long telephotos and zooms.

As for the other issues pertaining to TCs, They are pretty much covered.

to really take advantage of a TC the following are to be considered

Final Maximum aperture needs to be F6.7 or faster or AF will become totally unreliable, which means the following lens maximum apertures. For 1.4x TCs F4.5, for 1.7x TCs F4 and for 2x TCs F3.5.

Some TCs do not have correction for prime lens aperture (sigmas included) they just pass the lens info streight through, which causes metering errors on the K10D and K20D.

Similairly some TCs (Sigma included) just pass lens focal length and focusing data streight through, which means the focal length for SR is not optimal

Some TCs modify this data i.e. aperture and perhaps focal length, but these are older TCs and may not correctly communicate AF Info when used with newer lenses. hence as others have reported AF does not work

It is really a mixed bag because pentax never came out with its own AF teleconverter

Last edited by Lowell Goudge; 08-24-2009 at 08:03 AM.
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