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01-16-2010, 12:33 PM   #91
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Can you stack:
1. TC's of different brands, i.e; A Sigma-for-Pentax TC 1.4x plus a Tamron 1.4x
2. Different types of TC's, i.e: a 1.4x Tamron plus a Pentax A FA 1.7x adapter
JP

01-16-2010, 05:18 PM   #92
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QuoteOriginally posted by jpzk Quote
Can you stack:
1. TC's of different brands, i.e; A Sigma-for-Pentax TC 1.4x plus a Tamron 1.4x
2. Different types of TC's, i.e: a 1.4x Tamron plus a Pentax A FA 1.7x adapter
JP
Hi Jacques,

I do all the time. In AF TCs, I have a Tamron F 1.4x AF PZ MC4, a Sigma EX 1.4x APO, and a couple of Pentax F 1.7x AFAs.

I usually carry them all, and combine them if it's to my advantage. Order is sometimes important. The Sigma has a protruding front element, so you cannot it must be the one that attaches to the lens in any combination (considering that the lens has a recessed rear element). Any additional TCs (except for another Sigma) can be attached to the Sigma. With 2 1.4x TCs, you get the equivalent of a 2x in both magnification and light loss (2 stops). With a 1.7x + a 1.4x, you get the equivalent of 2.38x with @ 2.4 stops of light loss.

A few other thoughts about TCs:

I bought the Sigma because of build quality. The Tamron is probably a little better optically, but the Sigma feels more solid with its aluminum barrel, and I just trust it more when using a heavy lens like a 300/2.8. The Tamron works as well, it just doesn't allow as much confidence for me.

I like two stacked 1.4x TCs better than any of the 2x TCs I've tried, but I haven't tried the two best for the K mount, the Sigma EX 2x APO or the Pentax A Rear Converter-L which is MF, but probably easily the best optic available for the K mount of this type. Remember that you can't stack 2 Sigma TCs of any type because of the protruding front element of the TCs. The only 2x TCs I have are all MF -- the Vivitar "A" 2x MFTC, Pentax A 2x Rear Converter -S, and a Tamron SP 01F Adaptall 2, all considered very good, but IMO, they all fall a little short in optical performance, even with premium lenses.

Two P 1.7x AFAs can be stacked, but you must first focus the AFA attached to the lens to its infinity setting, then mount the second AFA. The AF function of the AFA can be disabled by shorting the Data pin (farthest away from the red dot on the mount) if one wants to use it with Focus Trap. The same is true of any AF lens. Aperture value is still transmitted, and full AE functionality is retained. You must short the pin, not insulate it, so tape is not an option if you want to retain AE capability.

SDM can definitely a (?) factor in TC use. I've found that my DA*50-135 just hunts and will not lock focus with my Tamron PZ compatible 1.4x. Others have said that this can work, so I'll take their word for it, but in my mind this only raises the compatibility rating to questionable. It's probably sample variation in the lens, but there's no way for me to be sure, so I'd still have to question whether stacked PZ TCs would work with SDM on the DA*300/4, even if a single TC works fine. AFAIK, Sigma claimed to have an HSM TC in the works, but I haven't seen it, and the APO and APO DG TCs don't have SDM/HSM contacts, so they can't AF with an SDM lens.

All the existing AF TCs, with the exception of the AFA, still transmit lens ID info to the body, so when used with AF lenses, you cannot correct the SR setting for the increased effective FL. With a 1.4x TC, this might not make enough of a difference to effect usability, but with 2x (stacked 1.4xs) and the resultant 2stop light gathering difference, this could cause some significant challenges with handholdability.

This is a significant difference from the functionality of the AFA, IMO. It does not relay lens ID information, so you can enter an appropriate FL when using it. Add that to its very good optical quality, Quick Shift and focus limiting functionality, and focusing speed, and IMO, you get the best TC to use for the K mount, for just about any lens. All of my SR bodies remember the AFA as a distinct lens, so focus corrections and SR FL information, once set, are remembered and used by the body -- in other words, if you set either focus correction or SR FL for the AFA and one lens, then change the lens, it will continue to use the previously set info which will probably be inappropriate for the second lens.

The last is a caveat -- Sample variation in lenses and TCs can all contribute to actual usability, either in AF operation or IQ. The combos that I use and like may not work as well with different samples. I will say that all 4 AFAs that I've had worked identically, AFAIC, so my conclusion is that there's very little sample variation in these. All of my AFAs have been older ones.

Scott

Last edited by snostorm; 01-16-2010 at 05:26 PM. Reason: added a few things
01-17-2010, 11:25 PM   #93
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BTW, double checked with my FA50/1.4 and A50/1.2.
With my k200d - the top deck reads f2.8 while on Av for either/both lenses.
01-18-2010, 10:24 AM   #94
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QuoteOriginally posted by snostorm Quote
Hi Jacques,

I do all the time. In AF TCs, I have a Tamron F 1.4x AF PZ MC4, a Sigma EX 1.4x APO, and a couple of Pentax F 1.7x AFAs.

I usually carry them all, and combine them if it's to my advantage. Order is sometimes important. The Sigma has a protruding front element, so you cannot it must be the one that attaches to the lens in any combination (considering that the lens has a recessed rear element). Any additional TCs (except for another Sigma) can be attached to the Sigma. With 2 1.4x TCs, you get the equivalent of a 2x in both magnification and light loss (2 stops). With a 1.7x + a 1.4x, you get the equivalent of 2.38x with @ 2.4 stops of light loss.

A few other thoughts about TCs:

I bought the Sigma because of build quality. The Tamron is probably a little better optically, but the Sigma feels more solid with its aluminum barrel, and I just trust it more when using a heavy lens like a 300/2.8. The Tamron works as well, it just doesn't allow as much confidence for me.

I like two stacked 1.4x TCs better than any of the 2x TCs I've tried, but I haven't tried the two best for the K mount, the Sigma EX 2x APO or the Pentax A Rear Converter-L which is MF, but probably easily the best optic available for the K mount of this type. Remember that you can't stack 2 Sigma TCs of any type because of the protruding front element of the TCs. The only 2x TCs I have are all MF -- the Vivitar "A" 2x MFTC, Pentax A 2x Rear Converter -S, and a Tamron SP 01F Adaptall 2, all considered very good, but IMO, they all fall a little short in optical performance, even with premium lenses.

Two P 1.7x AFAs can be stacked, but you must first focus the AFA attached to the lens to its infinity setting, then mount the second AFA. The AF function of the AFA can be disabled by shorting the Data pin (farthest away from the red dot on the mount) if one wants to use it with Focus Trap. The same is true of any AF lens. Aperture value is still transmitted, and full AE functionality is retained. You must short the pin, not insulate it, so tape is not an option if you want to retain AE capability.

SDM can definitely a (?) factor in TC use. I've found that my DA*50-135 just hunts and will not lock focus with my Tamron PZ compatible 1.4x. Others have said that this can work, so I'll take their word for it, but in my mind this only raises the compatibility rating to questionable. It's probably sample variation in the lens, but there's no way for me to be sure, so I'd still have to question whether stacked PZ TCs would work with SDM on the DA*300/4, even if a single TC works fine. AFAIK, Sigma claimed to have an HSM TC in the works, but I haven't seen it, and the APO and APO DG TCs don't have SDM/HSM contacts, so they can't AF with an SDM lens.

All the existing AF TCs, with the exception of the AFA, still transmit lens ID info to the body, so when used with AF lenses, you cannot correct the SR setting for the increased effective FL. With a 1.4x TC, this might not make enough of a difference to effect usability, but with 2x (stacked 1.4xs) and the resultant 2stop light gathering difference, this could cause some significant challenges with handholdability.

This is a significant difference from the functionality of the AFA, IMO. It does not relay lens ID information, so you can enter an appropriate FL when using it. Add that to its very good optical quality, Quick Shift and focus limiting functionality, and focusing speed, and IMO, you get the best TC to use for the K mount, for just about any lens. All of my SR bodies remember the AFA as a distinct lens, so focus corrections and SR FL information, once set, are remembered and used by the body -- in other words, if you set either focus correction or SR FL for the AFA and one lens, then change the lens, it will continue to use the previously set info which will probably be inappropriate for the second lens.

The last is a caveat -- Sample variation in lenses and TCs can all contribute to actual usability, either in AF operation or IQ. The combos that I use and like may not work as well with different samples. I will say that all 4 AFAs that I've had worked identically, AFAIC, so my conclusion is that there's very little sample variation in these. All of my AFAs have been older ones.

Scott
Hi Scott,

Thanks for the reply.

That is quite an essay regarding stacking TC's you have here.
I have read it twice already and still trying to digest all of the information which is nicely explained.
So, if I summarize - generally speaking - this means that one has to be careful with Sigma TC's because of their protruding front elements., and that most of the time you would be able to stack TC's. The order is also important when adding a AFA 1.7x adapter. I am still looking all over for one of these but prices are astronomical. Maybe when Pentax release theirs?
Of course, the faster the lens, the better because of the loss of one to two f-stops (or more), that I understand perfectly.

As soon as I get my hands on one of those Pentax 1.7x adapters, I will give this a go. Can't hardly wait to see what results I will get.

Cheers.

JP

01-18-2010, 01:42 PM   #95
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QuoteOriginally posted by jpzk Quote
Hi Scott,

Thanks for the reply.

That is quite an essay regarding stacking TC's you have here.
I have read it twice already and still trying to digest all of the information which is nicely explained.
So, if I summarize - generally speaking - this means that one has to be careful with Sigma TC's because of their protruding front elements., and that most of the time you would be able to stack TC's. The order is also important when adding a AFA 1.7x adapter. I am still looking all over for one of these but prices are astronomical. Maybe when Pentax release theirs?
Of course, the faster the lens, the better because of the loss of one to two f-stops (or more), that I understand perfectly.

As soon as I get my hands on one of those Pentax 1.7x adapters, I will give this a go. Can't hardly wait to see what results I will get.

Cheers.

JP
First, I think, tha Sigma Apo tcs are cheap, compared to what could be expected from Pentax - if they ever release a new tc at all.

Second, I think the Pentax 1.7x AF-adaptor is useful, but I am not that excited about it. With some lenses it is useable, with others, not. For instance, it would be great to use it with the Pentax 500/4.5. But the resulting chromatic aberrations are so massive, that it is unuseable (I've posted example images somewhere here). I think, I should give it a try with the 300/2.8, but haven't done so. I don't need it with any other lens, as I prefer using primes or good zooms without a tc.

The only tcs I use more often are the Sigma 1.4x Apo with the Sigma 70-200/2.8, because this combination gives results (IQ-wise), that are visibly not different from using the lens on its own (and that is a sharp lens). And then there is the Pentax 1.4x-L, which is simply the best tc available for Pentax. It teams up nicely with the 300/2.8 (Tamron 60B in my case) or even the 500/4.5 and other long glass.

Both 2x tcs (The Sigma Apo and the Pentax L) are still very good for 2x tcs, but noticeably "worse" (that is too hard an expression) than the 1.4x modells.

Ben
01-18-2010, 05:24 PM   #96
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QuoteOriginally posted by Ben_Edict Quote
...The only tcs I use more often are the Sigma 1.4x Apo with the Sigma 70-200/2.8...
is that the pre-HSM lens, or are you saying that is that working with the newer HSM version from Sigma. (I ask with fingers crossed ) I'm sure it's been discussed, but believe it or not I've never come across one of those threads, so I've been wondering.

@snostorm, you're my kind of TC user. Usually a vocal critic has come in blasting the idea of stacking TCs by now every time I've mentioned doing it... lol. ...As long as you can keep the assembly from flexing; bad results if not.
01-18-2010, 07:03 PM   #97
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QuoteOriginally posted by m8o Quote
is that the pre-HSM lens, or are you saying that is that working with the newer HSM version from Sigma. (I ask with fingers crossed ) I'm sure it's been discussed, but believe it or not I've never come across one of those threads, so I've been wondering.

@snostorm, you're my kind of TC user. Usually a vocal critic has come in blasting the idea of stacking TCs by now every time I've mentioned doing it... lol. ...As long as you can keep the assembly from flexing; bad results if not.
Hi m8o,

None of the Sigma TCs so far, at least have had PZ contacts, so will be MF with HSM/SDM lenses -- sorry. . .

I base my TC use on results, the most vocal critics usually have a preconceived notion that it can't possibly give good results, but haven't actually tried it themselves -- not exactly the best sources for info. . .

I started trying it as an experiment, and continued to use some combos because they gave pleasing results, so I keep using them. Anyone that can show me how to get AF at 714mm at under 7lbs and $3000 for the K mount, I'm willing to listen. . .

This one's with a DS, Tamron SP 300/2.8, SP140F 1.4x TC + P F 1.7x AFA , so in this case, we're talking an AF 714mm f6.7 lens for under $1000 USD . . . BTW, this was handheld.



and a 100% crop from the center of the frame:


Scott
01-19-2010, 02:08 PM   #98
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QuoteOriginally posted by snostorm Quote
...............

This one's with a DS, Tamron SP 300/2.8, SP140F 1.4x TC + P F 1.7x AFA , so in this case, we're talking an AF 714mm f6.7 lens for under $1000 USD . . . BTW, this was handheld.

Scott
Impressive results! Looks like some PF there but to get an image while handheld is impressive!

I'm trying to do the math here in terms of f-stop loss with stacked TC's:
F2.8 with 1.4x = f4? which I gather would still make it AF'able with the AFA 1.7X right?

01-19-2010, 02:51 PM   #99
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QuoteOriginally posted by m8o Quote
is that the pre-HSM lens, or are you saying that is that working with the newer HSM version from Sigma. (I ask with fingers crossed ) I'm sure it's been discussed, but believe it or not I've never come across one of those threads, so I've been wondering.

@snostorm, you're my kind of TC user. Usually a vocal critic has come in blasting the idea of stacking TCs by now every time I've mentioned doing it... lol. ...As long as you can keep the assembly from flexing; bad results if not.
sorry, screwdriver only, the tcs as well my lens.

Ben
01-19-2010, 03:29 PM   #100
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QuoteOriginally posted by PentHassyKon Quote
Impressive results! Looks like some PF there but to get an image while handheld is impressive!

I'm trying to do the math here in terms of f-stop loss with stacked TC's:
F2.8 with 1.4x = f4? which I gather would still make it AF'able with the AFA 1.7X right?
Hi PHK,

Thanks!

Some luck was definitely involved, but considering that it was with a DS, so no image stabilization, and was shot at 1/250 (or about 1.5 stops beyond the 1/FL "rule), I was really pleased. I posted this to show the resolution capabilities of the combo though. Mentioning that the shot was taken handheld was just bragging. . .

There is certainly some PF with the Tamron, but to get better performance in this regard at this spec, you'd have to go to either the Sigma EX 300/2.8 APO/APO DG of the FA*300/2.8 ED(IF), so it will cost between 1.5-4x the $s, and you still won't totally eliminate it. I have 8 lenses that cover 300mm, and none of them, including the FA*300/2.8 totally control PF in all situations. I've never considered it a deal breaker in a lens since I've developed a pretty good cure in PP.

You are correct to multiply the max lens Av by the magnification of the TC(s). To get f6.7, I just took 2.8 x 1.4 = 3.92 x 1.7 = 6.664 and rounded up. The exif shows f7.1, but that Av only takes into account the Av at the lens and the 1.7x AFA's calculation of its effect on Av. To get a closer effective Av of the shot, you still have to add the effect of the 1.4x TC, so the actual effective Av of the shot is 7.1 x 1.4 = f9.94 (f10 rounded up, and still only an approximation because the AFA generally rounds up in its calculation also). For all practical purposes, the lens was set to @ f4, or closed down @ 1 stop or less.

I do all final focusing with these combos using AF. My eyesight varies quite a lot during the course of a day, so I rely on AF probably more than the average shooter.

Scott
01-19-2010, 09:14 PM   #101
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Thanks for the samples and comments, guys!

Snowstorm,
That is a great pic of the cardinal. I am amazed at the precision wchieved with the TC combo. The lens you have used, the DS, Tamron SP 300/2.8, must be quite a beast!?
Is this the Model B (Adaptall II) or the DI ?
Is there a "better" pick for this type of lens, in the Tamron or Sigma brand?
For a while, I was debating whther I should start looking into a F2.8 300mm because it can be used with TC's better than a F4 300mm, i.e: the lens is simply much faster and allows for more latitude that way, especially when it comes to stacking TC's.
I don't believe I would get similar results with a F4 lens.

Thanks for sharing the pic and comments.

JP
01-20-2010, 06:17 PM   #102
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QuoteOriginally posted by jpzk Quote
Thanks for the samples and comments, guys!

Snowstorm,
That is a great pic of the cardinal. I am amazed at the precision wchieved with the TC combo. The lens you have used, the DS, Tamron SP 300/2.8, must be quite a beast!?
Is this the Model B (Adaptall II) or the DI ?
Is there a "better" pick for this type of lens, in the Tamron or Sigma brand?
For a while, I was debating whther I should start looking into a F2.8 300mm because it can be used with TC's better than a F4 300mm, i.e: the lens is simply much faster and allows for more latitude that way, especially when it comes to stacking TC's.
I don't believe I would get similar results with a F4 lens.

JP
Hi Jacques,

Thanks!

The Tamron is the Adaptall 2 (mod 60B) There is also a 360B which was a slightly updated model, still with the Adaptall 2 mount. Tamron also apparently made a very small run of the AF version of this lens in K mount. I've seen pictures and a few testimonials, but have never seen one actually offered, nor have I tried one, so I can't say anything about how the lens handles or shoots.

Both the Sigma EX 300 APO and APO DG (digitally coated) models control CA/PF better than the Tamron 60B, in my experience. They are also both AF models, and about twice (at least) as costly on the used market. I'd say the Sigmas are also a bit sharper, but possibly a little less contrasty which might be due to the protective front filter that's factory installed on the Sigmas.

It's hard to recommend that someone choose a 300/2.8 over a top shelf 300/4 class lens -- much harder than comparing lenses in shorter FLs. Most people wouldn't notice the difference in handling a 50/1.4 compared to a 50/2.8 or could handle a 200/2.8 as easily as a 200/4, but the difference between a 1kg 300/4 and a 3kg 300/2.8 is often the difference between shooting handheld and having to lug along a tripod and gimbal (in addition to carrying the lens) to get comparable results. Handholding a 300/2.8 effectively is a difficult proposition at best for me -- only possible for seconds at a time, and then only if one has some handholding skills (and some luck doesn't hurt). On the other hand, I rarely shoot a 300/4(.5) with any external support, even at 510mm with the 1.7x AFA, but the light has to be good enough to allow me to shoot at 1/125 or faster to get consistent results.

Scott

Last edited by snostorm; 01-20-2010 at 06:18 PM. Reason: added text
01-21-2010, 03:09 AM   #103
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QuoteOriginally posted by snostorm Quote
It's hard to recommend that someone choose a 300/2.8 over a top shelf 300/4 class lens -- much harder than comparing lenses in shorter FLs. Most people wouldn't notice the difference in handling a 50/1.4 compared to a 50/2.8 or could handle a 200/2.8 as easily as a 200/4, but the difference between a 1kg 300/4 and a 3kg 300/2.8 is often the difference between shooting handheld and having to lug along a tripod and gimbal (in addition to carrying the lens) to get comparable results. Handholding a 300/2.8 effectively is a difficult proposition at best for me -- only possible for seconds at a time, and then only if one has some handholding skills (and some luck doesn't hurt). On the other hand, I rarely shoot a 300/4(.5) with any external support, even at 510mm with the 1.7x AFA, but the light has to be good enough to allow me to shoot at 1/125 or faster to get consistent results.

Scott
That's very much my own experience. Though the Tamron 60B counts among the smaller and lighter 300/2.8s, I use it handheld mostly, if I can find a place to rest my elbow securely (window sill, a handrail etc.) Otherwise it goes on the tripod or monopod, which is already a big helper and much easier to carry around. I also keep my old A*300/4, which is simply dimunitive in size and easy to carry around, as it fits inside most of my bags, whereas the 2.8 requires an external LowePro lens bag (or the really bigger lens backpack). This is something, that should be considered, too.

Ben
01-21-2010, 04:03 AM   #104
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I used the tamron 360b for a good while and while mine was better with the adaptall 1.4x tc, the 1.7x worked very well except for the fringing. I usually stopped down to f9 - f13 (after the 1.5 stops added in) I sold it after getting the DA300mm f4 because the da and 1.7x was good even wide open and alot easier to use. I really wanted a fast 300mm that was useable at f2.8. I finally got one, but it is another brand.
01-22-2010, 09:48 AM   #105
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QuoteOriginally posted by m8o Quote
@snostorm, you're my kind of TC user. Usually a vocal critic has come in blasting the idea of stacking TCs by now every time I've mentioned doing it... lol. ...As long as you can keep the assembly from flexing; bad results if not.
If this had been posted on DPR he for sure would get some bashin'!!!

Good info Snostorm. All of us other forum members can benefit from your experience and all the time and effort you've put into this. Thanks!
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