[GibbyTheMole]

I've never had good luck with them, but then again all of them were cheap 2x TCs. The better 1.4x TCs are likely much better.

On all of them I've used, they lowered the contrast and made CA much worse.

I bought mine as old stock, new in box from a Forum member, Tom in Japan. I use it mostly with my Tamron 28-75/2.8 for near macro work ( maintains the 12" minimum focus"). Also works on Sigma 100-300/4 and my DA 50-135 if I need reach and don't have the Sigma. I'd love to see Pentax introduce a new one.

Iris & Butterfly are Tamron + Kenko, Moon is Sigma + Kenko example, Dancer is 50-135 + Kenko

[pacerr]

Worth? Compared to what?

A few decades ago, high quality telephoto lenses were relatively even more expensive than they are today and few non-pros could justify the expense of a 300-500mm tele lens. Film ASA's in the low-hundreds also severely limited the utility of a stopped-down tele lens. Nevertheless, the TC opened the door to a relatively low cost "long lens" for the expanding advanced amateur market -- and in my opinion did the intended job pretty well. It allowed the user of a fairly common 135mm lens to explore the world of 300mm lenses at a reasonable cost.

Today, it's a rare individual that doesn't have an AF 70-300mm lens within his economic reach. But to take an economy 1.5x or 2x TC and pair it with an economy 200-300mm consumer lens shouldn't be expected to match the dreamworld results we see in the new mix of experienced pros and "others" on the internet displays. Those high expectations just aren't going to be met with economy gear in the hands of inexperienced users. (And there's definitely a significant learning curve above the 135mm level!)

If your use/value for a TC is to explore the long telephoto range on a budget, or simply to be prepared to capture a picture you couldn't otherwise grab with a shorter lens in the field, a 6 oz, lens-extender half the size of a PC mouse in your pocket is a great bargain -- if you don't attempt to compare it with the other options you either weren't carrying or couldn't afford anyway.

Now, you're likely thinkin' "Well, just crop, sucker!" -- and most of the time I'm thinkin' I need stand-off distance for close-up situations. There's more than one reason to use a TC. Likewise, a 10-20mm extension ring can also make an impromptu close-focus lens out of a kit lens.

It's useful to think of TC's and other accessories from the Macgyer POV -- what can I do despite the lens I don't have with me -- rather than wishin' you had a lens that's not available for what ever reason. A 1.4x and 2x TC takes up little more than the space and weight of a 50mm lens in the field. The shot I might get with them without comparing to some super lens I didn't have is what counts.

But again -- use a TC on the longest lens available that produces acceptable results only when it makes sense to do so and if you're gonna carry one, get the best you can afford. Personally, I don't believe they're beneficial when used with less than the longest FL lens you have available at any given time.

I have all three Adaptall-2 TCs for the 90, 180 and 300 lenses and the Tamron AF 1.4 which sees service with the Tamron SP 28-75 and SP 24-135 AF lenses when it makes sense to use 'em.

But ya gotta compare results with what you have in hand, not with what you wish you had at the time.

H2

The Tamron Pz-AF 1.4 and the Kenko Pz-AF 1.5x Teleplus SHQ are essentially the same item from an optics standpoint. And the newer Promaster may be equivalent.

[pacerr]

Two examples using the Tamron Adaptall SP 180/2.5:

Pairs processed in Faststone Imag Viewer & Screen Capture. Minimal PP and cropping to match image size at 600x800. ISO 800, F6.7, K200D. EXIF shown.

Left image is actual size with lens + Ad-2 200F 2x TC + Pz-AF 1.4x TC.

Right image is lens only (180mm) cropped to match enlargement factor.
----------------
Birds at about 12 ft -



Fence at about 30 ft -



While it's possible to see a slight difference when compared side-by-side. the images made with TWO stacked TCs would be respectable if using TCs were the only way to use an ~500mm lens.

I wouldn't expect the results to be as comparable if using low-end consumer equipment.

H2

---

Last edited by pacerr; 02-14-2012 at 01:48 PM.

[demp10]

All depends on the output size you are targeting. You need a certain dpi for an acceptable print at a given viewing distance. That can be anything from 70 dpi (or less) for a poster size print to be viewed from across the room to more than 250 dpi for a 8x10 being viewed at arm’s length.

If the sensor’s resolution provides more than the needed dpi for the targeted size, you can crop without any image degradation down to the acceptable dpi level. Lower than that, you will see softness and blurriness.

Enlarging the projected image from any lens will make it softer, but if the lens out-resolves the sensor by a significant margin, then the enlarged softer image can still be within the sensor limits in which case you do not lose any quality. And since you can now print at a higher dpi you will get a better image as it will compare to a cropped and enlarged print.

On the other hand, if the sensor out-resolves the lens, you are out of luck and a teleconverter will produce a soft, fuzzy image. At this point it is a balancing act, between the fuzziness from the lens/teleconverter combo and the fuzziness from cropping and enlarging.

Another way to look at it, is that a lens/teleconverter combo vs. cropping will produce better results on low resolution sensors (e.g. K10D)than higher ones (e.g. K-5) for a given output size.

[littledrawe]

I would say yes Converters are worth it, but you have to find a good lens + converter combo. I have been using the Pentax A 1.4x-L rear converter and it is great with the lens I have it on now.
I had the Pentax F 1.7X AFA and it was fantastic on my tamron adaptall 2 300mm f2.8 but did not shine on some of my other lenses.

[littledrawe]

Ad-2 200F 2x TC

Would love to get ahold of one of those, I would be all over the adaptall telephotos if I had one!

[jpzk]

My point of view:

High quality and fast prime lens ... good to go with a TC but you would still loose IQ.

Other than that, I wouldn't use a TC: too much picture "degradation" (possibly the wrong tern used here)

That is the reason why I am looking forward to this Pentax 560/5.6 ... it shouldn't need a TC and hopefully will be just as good as my DA*300/4 which I did use with TC's but not with great results.

JP

[Lowell Goudge]

Two examples using the Tamron Adaptall SP 180/2.5:

Pairs processed in Faststone Imag Viewer & Screen Capture. Minimal PP and cropping to match image size at 600x800. ISO 800, F6.7, K200D. EXIF shown.

Left image is actual size with lens + Ad-2 200F 2x TC + Pz-AF 1.4x TC.

Right image is lens only (180mm) cropped to match enlargement factor.
----------------
Birds at about 12 ft -



Fence at about 30 ft -



While it's possible to see a slight difference when compared side-by-side. the images made with TWO stacked TCs would be respectable if using TCs were the only way to use an ~500mm lens.

I wouldn't expect the results to be as comparable if using low-end consumer equipment.

H2

Considering the shots with a TC are at much slower shutter speeds that can enhance shake and blurr I would say the comparison is unfair and biased toward croP shots. It would be better to compare at at least the same shutter speed to focal length ratio

[pacerr]

Considering the shots with a TC are at much slower shutter speeds that can enhance shake and blurr I would say the comparison is unfair and biased toward croP shots. It would be better to compare at at least the same shutter speed to focal length ratio

Granted that potential shutter speed blur vs. ISO is one of the trade-offs and a consideration when choosing between these two options. However, all of these shots were with a dead steady rest without SR and it was of insignificant effect in this case. My point was that used intelligently, quality optical items can potentially produce reasonably comparable IQ results even with stacked TCs vs. a bare lens cropped to match FoV.

Practical results in the field would be affected by MANY less controllable conditions; experience with the gear and personal technique being but one significant factor. (Those were shot through a dirty, double-paned window for instance.)

But, I'd reiterate that a longer FL solution may be desirable for reasons of limited shooting locations, FoV criteria or safe stand-off distance as well as simply to achieve greater telephoto reach. My caveat that using TCs is logically relegated to pairing with the longest 'good' lens available and only when no other solution is practical seems generally prudent.

Knowing that acceptable results can be achieved with certain trusted lens/body/TC pairings can make the gear load a lot lighter. E.g., I have a Tamron SP AF 24-135 + Pz-AF 1.4X TC combination that provides a satisfactory, although not superior, solution to lugging an additional 3 lbs of bulky SP 80-200/2.8 unless deemed necessary.

And knowing I can pair the 1.4x TC with the SP 180 to achieve the narrower FoV of a 250/3.5 without lugging around a 4 lb 360B to solve a high DR situation without extensive PP is nice too.

The SP 180 + 140F or 200F TCs easily out classes the Super Tak 300/4 I once owned and every AF 70-300 I've used. Not likely that's also true of the DA* 300; however. that wasn't in my bag last time I looked.


H2

[Greyser]

Looked at the reviews at B&H for Sigma and Vivitar. Reviews were pretty dismal. Although many complaints were about the auto camera functions. I am concerned with sharpness, not auto features.

Do you use a teleconverter? What was your experience?

Are TCs worth using? Yes, they are. However, as almost all posters above mentioned they are worth using when paired with very good to excellent lenses. I don't use TCs with zooms personally, but had a decent test samples with DA*60-250/4 and Sigma 100-300/4. To me primes are still better.

I was reluctant to use TCs for some time, preferring cropping. Last summer two great experts snostorm and brandrx taught me a lesson. After that I bought my precious FA*300/4.5 instead of DA*300/4 to be specifically paired with screw driven 1.4X TC to make portable and lightweight 400mm combo. I hope the samples below speak better than anything else. They all were shot with FA*300/4.5 and various TCs. All images are more or less cropped.

Vivitar Series1 1.4X AF



Tamron 1.4X Pz-AF



ProMaster 1.7X Spectrum 7 Z AF



Tamron 1.4X Pz-AF at about 75-100ft. distance



ProMaster 1.7X Spectrum 7 Z AF



Tamron 1.4X Pz-AF



And that is what the Tamron Adaptal-2 400/4 is capable of when paired with Adaptal-2 2X 200F flat field TC. Distance is 25-27ft. Wide open.




Edit: For some reason I'm not lucky with my Pentax 1.7X AFA. I'm fine pre-focusing manually. However, AF is inconsistent and not as reliable as I want it to be.

[Lowell Goudge]

For the record, I have 10 TCs and have used them all, some with good results some with bad results. I find them somewhat paired with lenses

I have the Tamron TC for my Tamron 200-500/5.6 zoom but find it a PITA to use because you need to take the mount off the lens. It basically sits in the case. in place of the Tamron TC, I use my sigma APO 1.4 and 2 x TCs with the 200-500 as well as with my APO 70-200/2.8 EX. OK that covers 3 TCs and 2 lenses

I hac
Ve a soligor and a Tamron 2x TC in M42 mount, I think the Tamron is a better unit I carry it when I have my M42 lenses because my M42 kit stops at 200mm and if I need reach the Tammy TC goes on. Ok that's 2 more TCs down

I have old vivitarn2x and 3x 4 element TCs the 2x is ok but the 3x is a joke. They don't get much use. I have a takumars-A 2x TC that I use only because it has A contacts, but again it is about on par with the Vivitar 2x. Ok that's 8 TCs in total

The remaining 2 get the rest of my work, I have the 1.7x AF TC that is semi perminantly paired with my K300/4. it is a great pair and the lens is just fast enough that the TC will reliably focus. Then I have a Vivitar 2x macro focusing TC that goes with my K mount MF kit

In short, the sigma TCs a great on good tele lenses, but the lenses they can be used on are limited due to design. The AF TC is a great all round but I really only use it for teles, and the macro focusing TC is a good way to get both reach and macro. Out of 10 I use 4 regularly and one just in case.

[thoughton]

Might have posted this before, but someone might find it of interest:

These informal tests were just to satisfy my own curiosity about lens sharpness with these TCs. I didn't concern myself with colour, noise, etc. All shot indoors with my K20D on my home-printed lens resolution chart.

These are all 1:1 centre crops. To be frank I don't see how anyone can compare TC results using 800px forum-sized images.

I moved the tripod back and forth to keep the fields of view roughly similar. No PP apart from brightness adjustments so they all looked similarly bright.

(The smearing you can see in the right-hand-side converging lines near the numbers 14-16 and 18-20 is a result of the laser printer's limited resolution, not the lens)

Sigma 70-200 f2.8 Mk1, no TC


Sigma 70-200 f2.8 Mk1, Sigma 1.4x TC


Sigma 70-200 f2.8 Mk1, Sigma 2x TC


Personally I think the Sigma 1.4x TC is an excellent teleconverter. Bump up the contrast a bit and it's hard to tell it apart from pics taken with the lens on its own.

The 2x TC is not so great

Heres a version of the three above images shown at the equivalent of 800px forum sizes. I've corrected the contrast in the 1.4x and 2x versions here, but still no sharpening. (Bare lens on the left, 1.4x in the middle, 2x on the right):



And here's another version with sharpening:

[Lowell Goudge]

My point was that used intelligently, quality optical items can potentially produce reasonably comparable IQ results even with stacked TCs vs. a bare lens cropped to match FoV.

I agree, the issue is "intelligent" use.

[Lowell Goudge]

Personally I think the Sigma 1.4x TC is an excellent teleconverter. Bump up the contrast a bit and it's hard to tell it apart from pics taken with the lens on its own.

The 2x TC is not so great

I guess the question I have is when you state Sigma 70-200/2.8 MK1 what version exactly do you have.

I have the APO 70-200/2.8 EX (non DG non Macro) This lens works very well when paired to the APO Teleconverter 2x EX DG, at least in my opinion. I also know that later releases of the sigma lens were reported not as sharp at 200mm.