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03-10-2014, 06:49 AM   #271
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QuoteOriginally posted by crewl1 Quote
Has anyone posted shots from this TC with the DA*300 wide open and shared AF behavior experiences yet?
If I missed it please let me know where thanks.
Check the last three pages

03-10-2014, 08:24 AM   #272
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QuoteOriginally posted by Barry Pearson Quote
If this Teleconverter has super IQ and AF with the DA* 300mm f/4, the DA* 60-250mm f/4, and the D-FA 100mm f/2.8 WR Macro, and is rubbish with every other lens, it will be worth every penny to me! If Ricoh/Pentax has compromised the quality of this Teleconverter with those lenses in order to make it work with lots of other lenses, I will be disappointed.

What I am saying is that we all have our priorities, and Ricoh/Pentax has to choose who to make happy in line with their own business objectives. They want to sell lots of Teleconverters, but they also want to sell lots of the three lenses I've identified above. And lots of K-mount bodies that work well with those top-end K-mount lenses plus the Teleconverter, for all of us nature, wildlife, motor-sport, and airshow photographers.

I have the Sigma 500mm f/4.5 APO EX DG, and of course I want it to work with that too! But I can get (and have) other Teleconverters that work with that lens. It is lower priority for me. (I also have another Sigma lens and a Samyang lens, and those are even lower priority).
Ok then fair enough I see everyone's point of view on this subject. The thing is for me I don't have any pentax lenses that I can use the TC with, that is why I am concerned about it being ok for my sigma and tamron lenses. I guess its a wait and see type of thing and watch the reviews on it and make a judgement, and/or buy the tamron and sigma TC to suit my lenses!
Thankyou all.

---------- Post added 03-11-14 at 12:27 AM ----------

QuoteOriginally posted by rawr Quote
Some may work, some may not. Just like with some of the existing TC from Pentax, Sigma, Tamron, Kenko etc. Even the existing Sigma TC won't work with all Sigma lenses.



I'd be reluctant to put any TC on either of those lenses, simply because of their slow apertures.
rawr I am not thinking of putting a TC with the lenses I mentioned to quicken the aperatures a TC is to boost the telephoto capability of the lens!
03-10-2014, 09:02 AM - 1 Like   #273
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QuoteOriginally posted by JASMAZ77 Quote
rawr I am not thinking of putting a TC with the lenses I mentioned to quicken the aperatures a TC is to boost the telephoto capability of the lens!
You don't get it. TC's don't just extend the reach of a lens, they darken the lens too.

A 1.4 TC will cut the light getting through your lens (any lens) by 1 stop. So a 70mm f2.8 becomes a 98mm f4, a 300mm f4 becomes a 420mm f5.6 etc. And a zoom like a Sigma 50-500mm f/4.5-6.3 even wide-open will become a f6 - f8 lens. Which may well have consequences for AF efficiency and optical performance.

I suggest you have a read of this:
The Pros and Cons of Using Teleconverters (Extenders) on your DSLR - Digital Photography School
03-10-2014, 10:02 AM   #274
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Hi,
Sorry if info was already related,
just tried FW update with my k-3 to check behaviour of non-Pentax TCs i own :
case 1 . Lens recognized by SLR ⇒ you get the non multiplicated focal length + unmodified aperture instead of only the second data
case 2. Lens not recognised by SLR : no change/ info.
I didn't compare AF when applicable.

03-10-2014, 11:47 AM   #275
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Quick try with Sigma 150-500. It doesn't translate the fstops, wide open fully zoomed the body shows f6.3. It focuses, and a quick shot didn't show me much for IQ. It is a bit long for hand held, so testing requires a tripod. I use the OS in the lens, so sending the focal length for inbody stabilization is not a concern.

I doubt if I will be using it with this lens.
03-10-2014, 07:58 PM   #276
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QuoteOriginally posted by Zygonyx Quote
Hi,
Sorry if info was already related,
just tried FW update with my k-3 to check behaviour of non-Pentax TCs i own :
case 1 . Lens recognized by SLR ⇒ you get the non multiplicated focal length + unmodified aperture instead of only the second data
case 2. Lens not recognised by SLR : no change/ info.
I didn't compare AF when applicable.
Zygonyx can you please explain what you have said in lamens terms? how does the new pentax TC work with non-pentax lenses.
03-11-2014, 01:15 AM   #277
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QuoteOriginally posted by derekkite Quote
Quick try with Sigma 150-500. It doesn't translate the fstops, wide open fully zoomed the body shows f6.3. It focuses, and a quick shot didn't show me much for IQ. It is a bit long for hand held, so testing requires a tripod. I use the OS in the lens, so sending the focal length for inbody stabilization is not a concern.

I doubt if I will be using it with this lens.
Given you say "I use the OS in the lens" its an HSM lens ?

If so this is good news as early reports indicated HSM did not function where 'some' hsm not functioning means a FW update from sigma may fix.
03-11-2014, 04:10 AM   #278
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QuoteOriginally posted by rawr Quote
You don't get it. TC's don't just extend the reach of a lens, they darken the lens too.

A 1.4 TC will cut the light getting through your lens (any lens) by 1 stop. So a 70mm f2.8 becomes a 98mm f4, a 300mm f4 becomes a 420mm f5.6 etc. And a zoom like a Sigma 50-500mm f/4.5-6.3 even wide-open will become a f6 - f8 lens. Which may well have consequences for AF efficiency and optical performance.

I suggest you have a read of this:
The Pros and Cons of Using Teleconverters (Extenders) on your DSLR - Digital Photography School
Ok then, how does it darken the lens? if the converter is between the lens and the front of the camera? is the light still coming through the front of the lens?

---------- Post added 03-11-14 at 08:18 PM ----------

QuoteOriginally posted by rawr Quote
You don't get it. TC's don't just extend the reach of a lens, they darken the lens too.

A 1.4 TC will cut the light getting through your lens (any lens) by 1 stop. So a 70mm f2.8 becomes a 98mm f4, a 300mm f4 becomes a 420mm f5.6 etc. And a zoom like a Sigma 50-500mm f/4.5-6.3 even wide-open will become a f6 - f8 lens. Which may well have consequences for AF efficiency and optical performance.

I suggest you have a read of this:
The Pros and Cons of Using Teleconverters (Extenders) on your DSLR - Digital Photography School
Thank you rawr I have just read the link sent me. In consideration of reading that I think a 1.4x TC will be more suitable and I will have to watch the light conditions and use more manual focus and choose which lens to use it with and how much aperature I will lose. On the other hand the article was written 7 years ago too so lens and auto focus technology have come a long way since then.

03-11-2014, 04:35 AM   #279
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QuoteOriginally posted by JASMAZ77 Quote
Ok then, how does it darken the lens? if the converter is between the lens and the front of the camera? is the light still coming through the front of the lens?
It does so by changing the focal length.
Aperture (f-number) is defined as focal length / Aperture (physical opening).
The physical aperture remains constant, the focal length increases - which means the f-number is increased as well.

For example, putting the 1.4X RC on an f/2.8 lens we'll get an f/(2.8*1.4 = 4) lens. One stop slower.
03-11-2014, 05:10 AM - 1 Like   #280
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QuoteOriginally posted by JASMAZ77 Quote
Ok then, how does it darken the lens? if the converter is between the lens and the front of the camera? is the light still coming through the front of the lens?

---------- Post added 03-11-14 at 08:18 PM ----------


Thank you rawr I have just read the link sent me. In consideration of reading that I think a 1.4x TC will be more suitable and I will have to watch the light conditions and use more manual focus and choose which lens to use it with and how much aperature I will lose. On the other hand the article was written 7 years ago too so lens and auto focus technology have come a long way since then.
As to the "darken the lens" question: The amount of light transmitted is the same as without the TC, but it's spread over a larger area so any given point on the sensor receives less light. You can demonstrate this yourself with a flashlight, er, sorry, a torch. Shine the light at a wall from a few feet away and wallk backwards. The light on any part of the wall gets dimmer, even though the light coming out the front of the torch hasn't changed. This is also the reason you need a different exposure with a flash at 20 feet than at 10 feet.
As to the 7 year old article: Yes, technology has changed, but the laws of physics haven't.
03-11-2014, 06:28 AM   #281
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QuoteOriginally posted by Parallax Quote
As to the "darken the lens" question: The amount of light transmitted is the same as without the TC, but it's spread over a larger area so any given point on the sensor receives less light. You can demonstrate this yourself with a flashlight, er, sorry, a torch. Shine the light at a wall from a few feet away and wallk backwards. The light on any part of the wall gets dimmer, even though the light coming out the front of the torch hasn't changed. This is also the reason you need a different exposure with a flash at 20 feet than at 10 feet.
As to the 7 year old article: Yes, technology has changed, but the laws of physics haven't.
I see your point Parallax, I know physics have not changed but the autofocus technology has changed on the camera's over the past 7 years.
03-11-2014, 06:57 AM   #282
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I'm using both the 1.4 and 1.7 and while things might change, not as much as you might think. I have an A-400 ƒ5.6 lens, the AF function works only at very close range in very bright light... on a K-3. Pentax recommends the 1.4 TC for use on ƒ4 lenses or faster. But it works poorly on my K-x even with an ƒ4 lens, works fine with a 2.8 lens though. You need a K-5 or newer. The limits of the technology have been pretty easy to define.It took about 15 minutes with a couple camera bodies and lenses. It's not rocket science.

But if you're still having trouble with the physics, look at the practical. K-x with DA*60-250, snappy accurate auto-focus. K-x with 1.4 TC and DA* 60-250, completely unreliable auto-focus, it might lock focus, it might not. To me, trying to explain why is a waste of time. You don't need to know why it works, you just need to know how it works, to be a photographer. Something I told my lens design instructor and the Photography Department Head on numerous occasions.
03-11-2014, 08:28 AM   #283
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QuoteOriginally posted by normhead Quote
I'm using both the 1.4 and 1.7 and while things might change, not as much as you might think. I have an A-400 ƒ5.6 lens, the AF function works only at very close range in very bright light... on a K-3. Pentax recommends the 1.4 TC for use on ƒ4 lenses or faster. But it works poorly on my K-x even with an ƒ4 lens, works fine with a 2.8 lens though. You need a K-5 or newer. The limits of the technology have been pretty easy to define.It took about 15 minutes with a couple camera bodies and lenses. It's not rocket science.

But if you're still having trouble with the physics, look at the practical. K-x with DA*60-250, snappy accurate auto-focus. K-x with 1.4 TC and DA* 60-250, completely unreliable auto-focus, it might lock focus, it might not. To me, trying to explain why is a waste of time. You don't need to know why it works, you just need to know how it works, to be a photographer. Something I told my lens design instructor and the Photography Department Head on numerous occasions.
Norm don't have a go at Pentax for a slow TC when you have an old Camera!! that is stupid!!
03-11-2014, 08:40 AM   #284
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QuoteOriginally posted by normhead Quote
I'm using both the 1.4 and 1.7 and while things might change, not as much as you might think. I have an A-400 5.6 lens, the AF function works only at very close range in very bright light... on a K-3. Pentax recommends the 1.4 TC for use on 4 lenses or faster. But it works poorly on my K-x even with an 4 lens, works fine with a 2.8 lens though. You need a K-5 or newer. The limits of the technology have been pretty easy to define.It took about 15 minutes with a couple camera bodies and lenses. It's not rocket science.

But if you're still having trouble with the physics, look at the practical. K-x with DA*60-250, snappy accurate auto-focus. K-x with 1.4 TC and DA* 60-250, completely unreliable auto-focus, it might lock focus, it might not. To me, trying to explain why is a waste of time. You don't need to know why it works, you just need to know how it works, to be a photographer. Something I told my lens design instructor and the Photography Department Head on numerous occasions.
I think that tells me why they updated the firmware on all the cameras Kr/K5 and newer. It would be interesting to see how it would do on a Kr under the same conditions because the Kr (before and after firmware update) and Kx are so close to each other.
03-12-2014, 09:57 AM   #285
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I called Lozeau and they had one, so I cancelled my order with Henry's. I am thrilled that I will have it for our trip to Mexico next week. I have a couple of birding trips planned.
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