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11-28-2011, 02:22 PM   #16
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I guess now's a good time to put my Tamron-F 1.4X Pz-AF MC4 on the market place

11-28-2011, 03:05 PM   #17
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I respect your comments falconeye, but there is more than one way to skin a cat.

QuoteOriginally posted by falconeye Quote
eliminate shake (1/250s on 300mm may not suffice with many tripods! Use separate flash or attach the camera to a big stone)
or you can use a long exposure where camera shake simply isn't an issue - about 5~10 second exposure with mirror lock up and even a half-decent tripod should deliver assessable results. Or you can use flash, and as an added bonus if you could include a metallic subject in the test scene that could give us an idea of how the TC's affect the levels of CA and LOCA in the scene. Ideally you should use two flash units at the same power level at a 45 degree angle relative to the focus plane.

QuoteOriginally posted by falconeye Quote
Use the lens' sweet spot aperture. For the 300/4.5, it is f/6.3 rather than f/5.6.
again, I think it is more reasonable to have a range of apertures involved in the testing to give us a more well-rounded perspective on how the TC's are helping or as the case may be, hindering the performance of the lens.

QuoteOriginally posted by falconeye Quote
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!
I don't get this, I know defocus blur can be a pain in the neck to eliminate but suggesting that LV isn't good enough is a going a bit far IMO. LV shows you exactly where the point of critical focus will be at the sensor level. At closer focus distances even with longer lenses the depth of focus at the sensor level is actually quite large - while at the other end of the lens depth of field becomes quite shallow, so there is a reasonable expectation that use of LV will produce satisfactory results.
11-28-2011, 03:14 PM   #18
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QuoteOriginally posted by twitch Quote
I guess now's a good time to put my Tamron-F 1.4X Pz-AF MC4 on the market place
What about comission?
11-28-2011, 04:22 PM   #19
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Greyser, of a study of AF performance was your interest, then the following factors should be considered:

1. did you do a focus fine calibration for each TC?
2. did you run a series of say, 8 shots ans select the best, for each TC?

I am asking this because, based on my own experience, not considering #1 and #2 can lead to arbitrary (read: random) sharpness conclusions.

The good truth in this is that performance with a good lens like the 300/4.5 and TCs is so good that these subtle factors need to be considered.

QuoteOriginally posted by Digitalis Quote
I respect your comments falconeye, but there is more than one way to skin a cat.
...
I don't get this, I know defocus blur can be a pain in the neck to eliminate but suggesting that LV isn't good enough is a going a bit far IMO.
You're right of course.

Except that LV isn't accurate enough for tests indeed. I measured AF accuracy in various situations and with the K-5, phase AF (if fine-tuned to the lens) can actually beat LV AF performance! But both are (in most cases) measurably off the point of best resolution when doing a focus series.

If you need a theory why this is so ...

LV doesn't may not read all pixels (lower resolution) and each focus motor has play so AF settles if "close enough" to true focus.

As for the tripod: Did you ever watch a 10x zoom LV display with a 500mm lens (1.4x300)? Did you then ever move your feet even on a concrete floor? Obviously not ... Many test sites leave out testing long lenses for this reason -- too hard to achieve reproducible results.

11-28-2011, 06:39 PM   #20
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QuoteOriginally posted by falconeye Quote
Except that LV isn't accurate enough for tests indeed. I measured AF accuracy in various situations and with the K-5, phase AF (if fine-tuned to the lens) can actually beat LV AF performance! But both are (in most cases) measurably off the point of best resolution when doing a focus series.
I see your point, however even phase AF can get dicey with slower lenses because it has less light to work with and of course there are the very tolerances that the physical hardware the AF system is built to - something has to give.

QuoteOriginally posted by falconeye Quote
LV doesn't may not read all pixels (lower resolution) and each focus motor has play so AF settles if "close enough" to true focus.
right, Supersampling Vs Subsampling.

QuoteOriginally posted by falconeye Quote
As for the tripod: Did you ever watch a 10x zoom LV display with a 500mm lens (1.4x300)? Did you then ever move your feet even on a concrete floor? Obviously not ... Many test sites leave out testing long lenses for this reason -- too hard to achieve reproducible results.
again a good point, a colleague of mine does holography and the efforts they go through to eliminate all possible sources of vibrations involves hideously expensive air-cushioned tables. However I wouldn't say testing long lenses is impossible it just requires rigorous adherence to long lens technique - a thing few people these days care for, or have the time to cultivate. I have tested many of my longer lenses 400mm and up and using ultra-short duration studio flash and a studio camera tree* and obtained perfectly satisfactory results.


*basically the biggest,heaviest tripod you can get - used exclusively in studios, the one I use weighs around 50Kg
11-28-2011, 09:47 PM   #21
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QuoteOriginally posted by falconeye Quote
Greyser, of a study of AF performance was your interest, then the following factors should be considered:

1. did you do a focus fine calibration for each TC?
2. did you run a series of say, 8 shots ans select the best, for each TC?

I am asking this because, based on my own experience, not considering #1 and #2 can lead to arbitrary (read: random) sharpness conclusions.

The good truth in this is that performance with a good lens like the 300/4.5 and TCs is so good that these subtle factors need to be considered.
You are talking about real AF testing. I was not testing the AF of these TCs. My intention was to test the resolving power of them to chose the best one to be paired with my FA*300/4.5. If you saw the crops, all of them are in focus, but sharpness and resolution are different, but not by a thick margin though. Of course I did lens micro adjustment and checked all TC to be within the provided DOF. If any of TC failed here I would not consider it convenient for every day use (ON/OFF micro adjustment exercise is not for me). I had my own system requirements and I was simply fulfilling them designing the practical test for it. I don't care what f-stop is optimal for testing, if I shoot mostly at f/4.5-5.6. In medium light conditions some TC would not AF at smaller apertures anyway. What the practical rational is behind of using 50kg steady tripod, if I'm going to hand hold the combo? From the other hand I'd like to use the most capable system possible. The approach was simplicity and practicality versus magazine style scientific testing. That's all. I've done enough scientific experiments in my life to value simplicity when it's possible.
11-29-2011, 06:09 AM   #22
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QuoteOriginally posted by Digitalis Quote
I have tested many of my longer lenses 400mm and up and using ultra-short duration studio flash and a studio camera tree* and obtained perfectly satisfactory results.

*basically the biggest,heaviest tripod you can get - used exclusively in studios, the one I use weighs around 50Kg
I mentioned using flash in my first post you replied to. You're right. And a flash (avoiding the full power setting) is good enough (read, fast enough) w/o a heavy tripod then.

QuoteOriginally posted by Greyser Quote
I've done enough scientific experiments in my life to value simplicity when it's possible.
You may be missing my point here. I say that you may have gotten random results. And you cannot know if this is the case or not because you didn't study if you have significant factors under control, like AF accuracy. To say it with Einstein: "Keep it as simple as possible. But no simpler." You went for simpler.

But don't take it as personal critics: I still think you did a great test and what you call "scientific magazine test" doesn't exist. Almost all magazine tests suffer from the same problems.

One minor detail though: I think that the aperture setting and AF ability aren't related. AF always happens with open aperture anyway.
11-29-2011, 09:01 AM   #23
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I think that falconeye has raised some good points, specifically not so much with respect to criticizing the test, it was interesting, but when you get into pixel peeping even if the subject is within the DOF range of the lens in theory, that really only applies to blowing up to 8 x 10, and not zooming in to assess the fine detail that might be in the individual pixel range.

I think this is where the comparison gets de-railed, to some extent. If you set up and run this test again, for example, do you get the same results?

For me, I think what you have from any of the TCs is acceptable, and I am not sure with your target, you can get any better. I think what may be more important, is the other aspects of the TCs now that y9ou have proven that they are all acceptably sharp.

What is the impact on metering,, with your camera, both normal exposure and P-TTL flash. what is the efficiency of each TC, i.e. real light loss of each, with the prime lens at the same aperture on each, do some cause exposure errors at different apertures, do some, under low light fail to get AF confirmation, while others work OK.

Determination of the BEST is not just the optical performance, because in real world shots, I am not sure you can tell these 5 apart.

11-30-2011, 12:32 AM   #24
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QuoteOriginally posted by falconeye Quote
One minor detail though: I think that the aperture setting and AF ability aren't related. AF always happens with open aperture anyway.
Agree. I don't remember what I meant to say there:ugh:
QuoteOriginally posted by falconeye Quote
You may be missing my point here. I say that you may have gotten random results. And you cannot know if this is the case or not because you didn't study if you have significant factors under control, like AF accuracy.
Theoretically yes. My practical take: if you have your 2D target within decent DOF window of you lens/combo, AF accuracy becomes redundant. I did not calculate it, but at 20ft and almost flat target, I assumed that I had enough DOF room not to worry about AF. And, yes, I did check and adjust it for FF/BF.
QuoteOriginally posted by falconeye Quote
did you run a series of say, 8 shots ans select the best, for each TC?
Why do you suggest running 8 shots may I ask? Do you know that for minimum sample size of 8 at confidence level 95% the max. failure rate to tolerate is 33%. It means that 33 out of 100 whatever you are going to test for samples might be a failure. For 90% confidence the failure rate is 27%. In biomedical industry we routinely test for 95% confidence and 5% max. failure rate, which require 59 samples to be randomized and tested. So, if you insist on running 8 test samples would you be satisfied with approx. 30% predefined failures?
Second: Even if I followed you advise on 8 samples, it would not really help. Let say, we are going to compare five (5) optical pieces. Each piece requires eight (8) shots to be made with some randomization. To do so at least you need to make a shot, switch to MF, re-set the focus manually, switch back to AF, and finally AF re-focus. Then switch back to MF, change the focus... and so on. Preferably you also need to run at least 3 separate test batches within your total sample size. Finally you will end up with 40 test images for pure non-instrumental and very subjective eyeball evaluation. Are you serious?

QuoteOriginally posted by Lowell Goudge Quote
when you get into pixel peeping even if the subject is within the DOF range of the lens in theory, that really only applies to blowing up to 8 x 10, and not zooming in to assess the fine detail that might be in the individual pixel range.
I'm not a pixel peeper at all. I was selecting the best resolving combo for myself. Then I made a mistake, when decided to share my results
QuoteOriginally posted by Lowell Goudge Quote
for me, I think what you have from any of the TCs is acceptable, and I am not sure with your target, you can get any better. I think what may be more important, is the other aspects of the TCs now that y9ou have proven that they are all acceptably sharp.
1. What's is wrong with my target? I explained already why I chose 2D target over 3D.
2.They all relatively sharp, you are right. And personally I'm going to stick with the Tamron from now
QuoteOriginally posted by Lowell Goudge Quote
What is the impact on metering,, with your camera, both normal exposure and P-TTL flash. what is the efficiency of each TC, i.e. real light loss of each, with the prime lens at the same aperture on each, do some cause exposure errors at different apertures, do some, under low light fail to get AF confirmation, while others work OK.
I did not care about all these stuff, what makes life miserable, not leaving time for real photography. BTW: all shots are very equally lit. I left them untouched, please see for yourself, if you are interested. The only noticeably darker is an output from the 1.7X AFA. But it was a total mistake to bring it for the shoot out among 1.4X TCs.
QuoteOriginally posted by Lowell Goudge Quote
I think this is where the comparison gets de-railed, to some extent. If you set up and run this test again, for example, do you get the same results?
I better stick my sharpest (proven ) Tamron 1.4X Pz-AF on FA*300 and go shooting.
QuoteOriginally posted by Lowell Goudge Quote
Determination of the BEST is not just the optical performance, because in real world shots, I am not sure you can tell these 5 apart.
Maybe not. But It's nice to believe that you shoot the best out of five. Don't you agree?
QuoteOriginally posted by Digitalis Quote
I think it is more reasonable to have a range of apertures involved in the testing to give us a more well-rounded perspective on how the TC's are helping or as the case may be, hindering the performance of the lens.
That's what people do for money. I usually go way further at work (non photography related though) to prove my concept. Seriously, why bother, if I use f/4.5-f/6.3 (in lens aperture terms, of course) most of the time?

I think I made a big mistake posting about my humble results here. On my way to my (and only my, please note) perfect light and sharp long telephoto solution I went through many wrong assumptions, mistakes, and financial losses. I used to search major forums and photo sites for a tiny grain of real knowledge, trying to learn from others. If I would be me half a year ago, I would appreciate this quick and dirty results. At least this knowledge would save me $250, spent on Sigma APO 1.4X EX DG, and $460, spent on 1.7X AFA. It costed me about $5K in total to come to the point where finally I'm not ashamed of my humble wildlife photography (IQ wise not artistic side of it, of course ). I'm really sick to make excuses for something what Iintentionally was not pursuing.
That's said, I will not be posting comparative shoot out here (quick and dirty, of course ) of FA*300/4.5 (alone and paired with 1.4x Tamron), Sigma 100-300/4 (alone and coupled with 1.4x undetermined for now TC) and DA*60-250/4 (again alone and with SDM capable 1.4X-1.7X TC). Have you noticed the 1.7X numbers? I have another TC on the way: the Promaster 1.7X Z AF, but that's another story.
Peace,
SG
11-30-2011, 06:57 AM   #25
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It seems my comments have perhaps not been fully understood, so I will put the point much more simply, I think all the TCs tested, within the range of possible errors are, from an optical point performing equally, and to get to a "best" decision, needs to consider all the aspects of the TC, and not just the optical performance.

While optical performance is nice, once you get to the point of proving equal, which I think Greyser has done, my experience with the other issues may lead me to take one TC over another, depending on shooting conditions.

For example, consider I own the SMC-F 1.7x AF TC,the sigma APO 1.4x EX and Sigma APO 2x EX DG teleconverters, and might just plan to use one of them on my Sigma APO 70-200F2.8 EX zoom.

On my K10D, if I just needed a quick shot without much thinking, I might actually prefer the Pentax TC because it reports the true (TC corrected aperture) to the camera and metering will be correct with that combo without any adjustments, in all modes. The sigma TCs do not correct aperture and the K10D is known for metering errors if true aperture is not known, and while this can be adjusted for in Av mode, it cannot in Manual (no ev comp in manual on the K10D) so unless you are really thinking about the situation, you are likely to meter wrong, the Pentax TC takes less thinking, therefore will have a higher probability of a grab and shoot correct exposure.

it is intangables like this that can drive one to be ranked best even if optical performance is inferior.

Same applies to flash photography. Unless you are using an *istD, and TTL flash vs P-TTL on newer bodies, a TC screws up flash performance. I use flash for wild life, and therefore accurate flash meteirng is important to me, minimal fuss is also important, as it impacts getting the shot right first time.

Otherwise, I have no issue, pick which ever you feel you get the best shots with, but it may be worth trying each in the field to see how they perform in the real world., after all, I don't usually come across paper bills on a flat wall in the woods
11-30-2011, 10:00 PM - 1 Like   #26
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QuoteOriginally posted by Lowell Goudge Quote
It seems my comments have perhaps not been fully understood, so I will put the point much more simply, I think all the TCs tested, within the range of possible errors are, from an optical point performing equally, and to get to a "best" decision, needs to consider all the aspects of the TC, and not just the optical performance.

While optical performance is nice, once you get to the point of proving equal, which I think Greyser has done, my experience with the other issues may lead me to take one TC over another, depending on shooting conditions.

For example, consider I own the SMC-F 1.7x AF TC,the sigma APO 1.4x EX and Sigma APO 2x EX DG teleconverters, and might just plan to use one of them on my Sigma APO 70-200F2.8 EX zoom.

On my K10D, if I just needed a quick shot without much thinking, I might actually prefer the Pentax TC because it reports the true (TC corrected aperture) to the camera and metering will be correct with that combo without any adjustments, in all modes. The sigma TCs do not correct aperture and the K10D is known for metering errors if true aperture is not known, and while this can be adjusted for in Av mode, it cannot in Manual (no ev comp in manual on the K10D) so unless you are really thinking about the situation, you are likely to meter wrong, the Pentax TC takes less thinking, therefore will have a higher probability of a grab and shoot correct exposure.

it is intangables like this that can drive one to be ranked best even if optical performance is inferior.

Same applies to flash photography. Unless you are using an *istD, and TTL flash vs P-TTL on newer bodies, a TC screws up flash performance. I use flash for wild life, and therefore accurate flash meteirng is important to me, minimal fuss is also important, as it impacts getting the shot right first time.

Otherwise, I have no issue, pick which ever you feel you get the best shots with, but it may be worth trying each in the field to see how they perform in the real world., after all, I don't usually come across paper bills on a flat wall in the woods
Lowell, I perfectly understand what you are talking about. And I agree with you. In your case you choose from very different TCs: 1.4X, 2X, and autofocusing on its own 1.7X AFA.

I did try three TCs in the field before testing them. You were right again. The difference was subtle. However the shooting conditions and subjects were different. Despite good performance the Vivitar at this point was unknown breed. The only piece that was not field tested was the Tamron (it arrived right before Thanksgiving, and I was planning the test on holiday longer weekend). From the very first glance I noticed that my Vivitar is a re-branded Tamron 1.4X. So, I got even more curious which one is better, because I had four good quality 1.4X TCs at once. I set up a few simple goals to test for in identical shooting conditions: sharpness, contrast, and possible light fall off. As you possibly noticed, all images are pretty close. The only Sigma APO EX DG output is less contrasty. But these tiny things are very easy to correct in PP. The resolution is a different story. I did not have intention to get absolute answer. I just tried to keep it simple. My goal was to find the best pair to my FA*300/4.5. The secret of my Tamron maybe is even simpler than we discuss. It might be that the two pieces of optics are just a perfect happy match. At the same time I suspect that both Sigmas will shine when being tested with Sigma 100-300/4.
As I said before, I used to read a lot of similar simple quick and dirty home tests; sometimes even a few similar shots posted as a test, and I really appreciated these efforts. Don't you agree that in the lack of information about something even some tiny bits of real test photos are better than nothing? I shared my results, trying to pay back to community my debts of borrowing somebody else knowledge in the past. I would be glad, if somebody would not be scared buying the Vivitar Series1 1.4X AF. It's cheap, available brand new, and is of very good quality (again it is re-branded Tamton 1.4x). It definitely worth a try in my opinion. Or somebody gets warned that very expensive Sigma EX DG might not be the best choice to be paired with Pentax lenses. Instead I was lectured how many samples I should run, how many multiple settings I missed to test, that my simple shoot out is not a valid test, etc., etc., etc. It's OK, but let me repeat one more time: I had no intention to perfectly test my combos. I just simulated my own shooting conditions to simplify the work, having a goal of finding the best match for my FA*300. That's all.
12-01-2011, 07:10 AM   #27
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I don't disagree that what you have done is useful, and does show something about performance. As you say, samples are better than no samples or unqualified Blah, Blah, Blah....

to that end, you are to be commended for taking the time and sharing the data.

The points I raised, are really the difference between the way they perform in the lab (given the possible test variances pointed out by falconeye) and the way they perform in the field and on cameras.

It would actually be a great outing to have a group of shooters who have a bagfull of different TCs to try them out on real subjects in the field but as you point out, getting comparable images can be a pain.

Sadly, we are all tired of photographs of ducks and seaguls
12-01-2011, 07:54 AM   #28
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QuoteOriginally posted by Lowell Goudge Quote
Greyser

I don't disagree that what you have done is useful, and does show something about performance. As you say, samples are better than no samples or unqualified Blah, Blah, Blah....

to that end, you are to be commended for taking the time and sharing the data.

The points I raised, are really the difference between the way they perform in the lab (given the possible test variances pointed out by falconeye) and the way they perform in the field and on cameras.

It would actually be a great outing to have a group of shooters who have a bagfull of different TCs to try them out on real subjects in the field but as you point out, getting comparable images can be a pain.

Sadly, we are all tired of photographs of ducks and seaguls
Amen!
12-01-2011, 12:11 PM   #29
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QuoteOriginally posted by Lowell Goudge Quote
It would actually be a great outing to have a group of shooters who have a bagfull of different TCs to try them out on real subjects in the field but as you point out, getting comparable images can be a pain.
That's actually the real challenge: to master the very long FL resulting from e.g., a TC with 300mm+.

I sometime use the Pentax 1.7x TC with a Sigma 500/4.5 APO, a combo which gives me AF. Below is a shot I took from outside a park during a flight show, i.e., I was much more far away than the visitors in the foreground. It's slightly cropped to 1000mm (1540mm equivalent FoV).

I can assure you that TC quality is your least of problems when taking such shots in a real world situation
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12-01-2011, 12:33 PM   #30
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QuoteOriginally posted by falconeye Quote
That's actually the real challenge: to master the very long FL resulting from e.g., a TC with 300mm+.

I sometime use the Pentax 1.7x TC with a Sigma 500/4.5 APO, a combo which gives me AF. Below is a shot I took from outside a park during a flight show, i.e., I was much more far away than the visitors in the foreground. It's slightly cropped to 1000mm (1540mm equivalent FoV).

I can assure you that TC quality is your least of problems when taking such shots in a real world situation
As a regular shooter with a K300/4 and the 1.7x AF TC, I can assure you the TC has nothing at all to do with the quality, or more probably the lack thereof, in my reject pile.

My number one complaint is why cant the damm bird just sit still???

Shake reduction is great, as far as it goes, and I am sure you have seen my immature heron shot at 1/40th hand held, (if not look in the sample archive under the 1.7x AF TF) but more often than not, birds move so unexpectidly that they are just a blurr at the edge of the frame. That's one reason why Ilike using a flash to freeze the birds, but in your shot, you would need one as bright as the sun to reach out that far
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