[Greyser]

Due to image attachment limitations here I posted my shoot out in DPR Pentax SLR forum:
Pentax SLR Talk Forum: Digital Photography Review
The following TCs were tested:
1. Tamron-F 1.4X Pz-AF MC4
2.-3. Vivitar Series1 1.4X AF and Sigma APO 1.4X EX
4. Sigma APO 1.4X EX DG
5. Pentax 1.7X AFA
All originals for download and further cropping are here:
https://picasaweb.google.com/111077764509465751575/FA30045AllShortTCShootOut...DfCEiQf2uTkWiw
Please feel free to ask any questions about the results.
SG

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Last edited by Greyser; 02-14-2012 at 11:29 PM.

[pcarfan]

Thank you

[Lowell Goudge]

i think the biuggest issue here is minor focus errors and not a good representation of the lenses / TCs used.

a 3D subject would have been much better than a flat subject. I would be willing to bet that it would be possible to make any one of the TCs look sharper.

[Digitalis]

the vivitar is surprisingly good, though corner crops would tell the tale a bit better.

[Lowell Goudge]

the vivitar is surprisingly good, though corner crops would tell the tale a bit better.

maybe, but the TC is probably a full frame converter, therefore anything on a DSLR would show favoourable results

[falconeye]

Due to image attachment limitations here I posted my shoot out in DPR Pentax SLR forum:
Pentax SLR Talk Forum: Digital Photography Review
The following TCs were tested:
1. Tamron-F 1.4X Pz-AF MC4
2. Sigma APO 1.4X EX
3. Vivitar Series1 1.4X AF
4. Sigma APO 1.4X EX DG
5. Pentax 1.7X AFA
All originals for download and further cropping are here:
https://picasaweb.google.com/111077764509465751575/FA30045AllShortTCShootOut...DfCEiQf2uTkWiw
Please feel free to ask any questions about the results.
SG

I applaud your effort.
Unfortunately, as in most such tests, no conclusions can be derived.

A number of points to watch in similiar tests:
- have high contrast in the subject (done, great!)
- provide crops (done, great!)
- eliminate defocus blur, either by a focus series or by small enough aperture. 300mm/5.6 or 54mm is still a big aperture! Manual focus or LV focus is not good enough!
- eliminate shake (1/250s on 300mm may not suffice with many tripods! Use separate flash or attach the camera to a big stone)
- Use the lens' sweet spot aperture. For the 300/4.5, it is f/6.3 rather than f/5.6.
- Have detail near the sensor's Nyquist frequency, like a measurement scale in the proper distance or a star chart. Because contrast decreases more quickly than resolution with such combos.

[Lowell Goudge]

I applaud your effort.
Unfortunately, as in most such tests, no conclusions can be derived.

A number of points to watch in similiar tests:
- have high contrast in the subject (done, great!)
- provide crops (done, great!)
- eliminate defocus blur, either by a focus series or by small enough aperture. 300mm/5.6 or 54mm is still a big aperture! Manual focus or LV focus is not good enough!
- eliminate shake (1/250s on 300mm may not suffice with many tripods! Use separate flash or attach the camera to a big stone)
- Use the lens' sweet spot aperture. For the 300/4.5, it is f/6.3 rather than f/5.6.
- Have detail near the sensor's Nyquist frequency, like a measurement scale in the proper distance or a star chart. Because contrast decreases more quickly than resolution with such combos.

Your comments made me go back and look at the results again, and there are a couple of additional points to consider. BTW I agree with your comments, specifically focus blurr, and use of flash, however that is one of the points I will discuss further below.

I don't see any mention of how focus was actually achieved? It would be interesting to know for certain, i.e. live view, manual or auto focus. THis is specifically because the lens and any 1.4x to 1.5 x TC would be at the limit of reliable AF confirmation for auto focus. To add onto that, the SMC-F 1.7x AF converter is about 1/3 of a stop beyond reliable AF ability, which is really only reliable at F4 and below.

There is mention of deliberate under exposure, due to the use of the TC, however this is not correct, and will be a finction of the TC and the camera. SOme TC's, specifically the SMC-F 1.7x AF converter, but perhaps others, modify the aperture data and feed true aperture back to the camera, and should not require any adjustment, additionally some cameras are quite reliable in metering, others (K10D and K20D specifically) are very poor if the true aperture is not known, therefore the compensation should or could be different for each. A better way to do this would be to use a constant exposure value for all the sample shots, however, this gets difficult because the 1.7x will need a different lens setting to the others.

Also, along the lines of constant exposure etc, how was this really controlled, because if some TCs modify the maximum aperture setting, then when setting to F5.6 may result in a different true and total aperture than other lenses?

Also depending on control of exposure etc, if the variables of each TC and aperture reporting are correctly compensated for, using a true constant exposure would show the efficiency of each TC and that would also be of interest.

As for flash, I agree, but again, this is very highly dependant on whether the TC properly corrects for the maximum aperture. Unless the flash was set to manual, there could be highly varrying results.


Aside from the issues above, all of which should be addressed, the actual resulting images are all quite good, and show that using a good TC on a good lens can produce acceptable images.

[Greyser]

I applaud your effort.
Unfortunately, as in most such tests, no conclusions can be derived.

A number of points to watch in similiar tests:
- have high contrast in the subject (done, great!)
- provide crops (done, great!)
- eliminate defocus blur, either by a focus series or by small enough aperture. 300mm/5.6 or 54mm is still a big aperture! Manual focus or LV focus is not good enough!
- eliminate shake (1/250s on 300mm may not suffice with many tripods! Use separate flash or attach the camera to a big stone)
- Use the lens' sweet spot aperture. For the 300/4.5, it is f/6.3 rather than f/5.6.
- Have detail near the sensor's Nyquist frequency, like a measurement scale in the proper distance or a star chart. Because contrast decreases more quickly than resolution with such combos.

Thank you for applauses . I had no intentions to setting up any scientific tests (bored already with those randomized studies, Cpk, LTL, worst case scenarios, etc.). I simply simulated my own regular shooting conditions. I even shoot at ISO 800 for the BIF situations sometimes. However, I rarely shoot the combo at f/6.3. Most of the time I don't care about corners sharpness, for example. And for manual live view focus exercises at 800mm I have Tamron 400/4 paired with 200F flat-field TC. I, maybe, should not include 1.7X AFA due to its own AF fluctuations. But again my intention was to figure out what is the best TC out of mine and only mine group of short range TCs paired with very specific lens for my very specific shooting conditions: wildlife photography during light brisk walks and hikes with no tripod/monopod use.
I learned something new from my experiments and wanted to share that Sigma APO is not always the best; and relatively cheap grey horse Vivitar 1.4X AF is a rebranded highly praised Tamron 1.4X Pz-AF with no Pz ability. There is no absolute truth here; everything depends on shooting conditions and style. But you are right: it might confuse somebody. Let me copy and put here the same disclaimer, what I posted in original DPR thread.
Disclaimer: ...please note that all conclusions below are made in regards to my copies of TCs paired with my copy of FA*300/4.5. I cannot guarantee that other copies would have the same IQ output.

[Greyser]

the vivitar is surprisingly good, though corner crops would tell the tale a bit better.

Sorry, I going for work and can't reply to everybody now. regarding the corners. Due to my shooing style I don't care about corner sharpness too much. However I include the special hight resolution targets in the corners. You are welcome to download the originals and try for yourself.

[Greyser]

Due to image attachment limitations here I posted my shoot out in DPR Pentax SLR forum:
Pentax SLR Talk Forum: Digital Photography Review
The following TCs were tested:
1. Tamron-F 1.4X Pz-AF MC4
2. Sigma APO 1.4X EX
3. Vivitar Series1 1.4X AF
4. Sigma APO 1.4X EX DG
5. Pentax 1.7X AFA
All originals for download and further cropping are here:
https://picasaweb.google.com/111077764509465751575/FA30045AllShortTCShootOut...DfCEiQf2uTkWiw
Please feel free to ask any questions about the results.
SG

I was interested exclusively in AF performance. So all shots are done with AF.

[Greyser]

Thank you

My pleasure. I hope it'll help somebody to go through the TC choices.

[Greyser]

i think the biuggest issue here is minor focus errors and not a good representation of the lenses / TCs used.

a 3D subject would have been much better than a flat subject. I would be willing to bet that it would be possible to make any one of the TCs look sharper.

From my own experience the 3D targets are more subjective giving sometimes more questions than answers. I had no intention of any real "scientific" testing. I just tried to find out what is the best short range TC, out of five I own, for my FA*300/4.5. The flat complex target that represents fine details of the wild life at real shooting distance was my choice based on my shooting style and preferences.

[Greyser]

the vivitar is surprisingly good, though corner crops would tell the tale a bit better.

Feel free to download the original files and check any crop you want. Please see the link in OP. It appeared that Vivitar is rebranded highly praised Tamron 1.4X Pz-AF with no Pz ability (doesn't work with SDM lenses).

[Lowell Goudge]

From my own experience the 3D targets are more subjective giving sometimes more questions than answers. I had no intention of any real "scientific" testing. I just tried to find out what is the best short range TC, out of five I own, for my FA*300/4.5. The flat complex target that represents fine details of the wild life at real shooting distance was my choice based on my shooting style and preferences.

understood. my idea about 3D targets was more aimed at the ability to resolve fine details and perhaps assess slight focus errors, between tests. if you had, for example, a small stuffed bird as the target, then if one lens focused slightly in front or behind, you would be able to see that and perhaps make a better assessment ( or just state equal performace) and be able to understand this is largely a focus error issue.

but I still think my last statement is quite appropriate, I think all the results are quite acceptable, and in a real world situation I suspect you would not be able to tell them apart, especially if you tuned your camera focus for each.

In reality I think any good TC will only be as good as the prime it is connected to, and a bad prime is just that a bad prime, lens characteristics, especially Laterall CA will only be amplified, but simple math says when you multiply zero by anything, you still have zero.

[Greyser]

understood. my idea about 3D targets was more aimed at the ability to resolve fine details and perhaps assess slight focus errors, between tests. if you had, for example, a small stuffed bird as the target, then if one lens focused slightly in front or behind, you would be able to see that and perhaps make a better assessment (or just state equal performace) and be able to understand this is largely a focus error issue.

I do 3D targets shoot out sometimes, but they usually add too many variables. Nicely set 2D target gives less trouble and quicker answers. Also I had my lens micro adjusted and all TC combinations tested with it for AF before the final shoot out. And you are right, in real life the margin might be even thinner. However, I feel better when using better resolving combo in general. I hope you know what I mean?

but I still think my last statement is quite appropriate, I think all the results are quite acceptable, and in a real world situation I suspect you would not be able to tell them apart, especially if you tuned your camera focus for each.

That is another problem. The camera doesn't see the TC attached. If your lens+TC combo needs different than lens AF fine tuning it's very inconvenient to do so manually (all lenses choice via menu ON before and OFF after shooting). Luckily enough all TCs in the test group fell within the main lens adjustment DOF window. And I used f/5.6 (or f/10 equivalent for the 1.7X AFA) to have the DOF more forgiving. That's another reason for use a 2D target.

In reality I think any good TC will only be as good as the prime it is connected to, and a bad prime is just that a bad prime, lens characteristics, especially Laterall CA will only be amplified, but simple math says when you multiply zero by anything, you still have zero.

Or vice versa: if you multiply 100% performing lens by zero performing TC, you get also a zero, right? I'm not a pixel peeper, but I'd like to have the best TC to be paired with my fabulous FA*300/4.5 (especially when I own all of them already ). I chose the FA*300 over the DA*300 mostly for one reason: ability to be coupled with screw driven TC to get 400-500mm output.