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03-26-2015, 09:20 AM   #1
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Pentax DA* 50-135 + 2x TC = F-stop ?

Hello PF Friends.

This goes for all non-aperture setting/indicator lenses I know.

What is the Fstop when I attach my manual only 2x TC? I also know to subtract a stop or two for the tc, yea
I imagine the lowest (meaning lowest number/widest aperture) but don't want to assume so you guys go ahead and shoot

Thanks!
John


Last edited by Iksobarg; 03-26-2015 at 12:38 PM.
03-26-2015, 09:34 AM   #2
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what did the TC cost? I bought a cheap one and it's pure crap on my DA 50-135 so I'm going to spend $450 or so on the new Pentax HD 1.4 TC.
03-26-2015, 10:21 AM   #3
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It's an old Japanese rebranded "Revue." And it's pretty good!
I've been looking for an ideal birding lens and after looking since a month I realized the 2x on the da* was an improvement over my FA80-320, spelled "b-u-d-g-e-t lens"

Last edited by Iksobarg; 03-26-2015 at 12:37 PM.
03-26-2015, 10:53 AM   #4
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The 50-135 is so sharp i've had really good results doing near 100% crops. might be better than a cheapo 2x converter.

03-26-2015, 10:59 AM   #5
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QuoteOriginally posted by Iksobarg Quote

What is the Fstop when I attach my manual only 2x TC?

Thanks!
John
I am curious as to what you mean by manual only TC. Some older manual TCs require your lens to have aperture ring.
03-26-2015, 11:02 AM   #6
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F 5.6
03-26-2015, 11:04 AM   #7
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QuoteOriginally posted by Iksobarg Quote
What is the Fstop when I attach my manual only 2x TC?
You lose 2 stops. Is that your question? With the Pentax HD TC 1.4 you will only lose 1 stop.

---------- Post added 03-26-15 at 01:05 PM ----------

QuoteOriginally posted by GaryH Quote
F 5.6
Oh.......what Gary said
03-26-2015, 11:41 AM   #8
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In retrospect by manual TC I meant it has no contacts.

---------- Post added 03-26-15 at 07:57 PM ----------

But back to my question. What Fstop is my lens fixed at when I throw the TC on?

03-26-2015, 12:03 PM   #9
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QuoteOriginally posted by Iksobarg Quote
In retrospect by manual TC I meant it has no contacts.

---------- Post added 03-26-15 at 07:57 PM ----------

But back to my question. What Fstop is my lens fixed at when I throw the TC on?
It's a moving target. Every time you increase your F stop, it goes up by 2.
03-26-2015, 12:19 PM   #10
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QuoteOriginally posted by Iksobarg Quote
In retrospect by manual TC I meant it has no contacts.
QuoteOriginally posted by Iksobarg Quote
What is the Fstop when I attach my manual only 2x TC?
GaryH has always answered, but to elaborate:

With a lens with no aperture ring and a manual TC, the lens will always be fully open. Thus with your partcular lens, (max. aperture f/2.8) the aperture ratio with a 2X TC will be 1:2.8 x 2 = 1:5.6
03-26-2015, 12:35 PM   #11
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Hey G.Stone! Good to hear from you. It's been a while. o/
On the Fstop: I sorta figured that. It simply makes sense.

Thanks all for your responses.

Tweaking the topic a little; I've perused many a thread and videos on the subject of birding and sort of arrived at the conclusion that a Da* 300 with a 1.4 TC would be close to ideal. One main issue I have with it is the inability to zoom out and home in on target birdie. Anyway for now I'm all for a manual setup and willing to live with lost or botched shots until I decide to $pend on some serious AF birding glass.

---------- Post added 03-26-15 at 08:39 PM ----------

Just for fun, I'll followup with posting some shots... tomorrow.
03-26-2015, 12:41 PM   #12
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QuoteOriginally posted by Iksobarg Quote
Hey G.Stone! Good to hear from you. It's been a while. o/
On the Fstop: I sorta figured that. It simply makes sense.

Thanks all for your responses.

Tweaking the topic a little; I've perused many a thread and videos on the subject of birding and sort of arrived at the conclusion that a Da* 300 with a 1.4 TC would be close to ideal. One main issue I have with it is the inability to zoom out and home in on target birdie. Anyway for now I'm all for a manual setup and willing to live with lost or botched shots until I decide to $pend on some serious AF birding glass.

One last note. I have SMC Pentax-FA 100-300mm F4.7-5.8 and since it has an Aperture Ring it can be used with a manual TC. You will obviously need good light and a tripod but you can find the 100-300mm for fairly economical prices if you are patient and look.

Here is an example that is near me. Pentax 35 mm kit with lenses bag... Everything you need $80 and it comes with a free film body, 28-70, bag, filter and a few gadgets. You could probably sell the rest of what you get for close to the cost of the 100-300.
03-26-2015, 01:28 PM   #13
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QuoteOriginally posted by Mistlefoot Quote
One last note. I have SMC Pentax-FA 100-300mm F4.7-5.8 and since it has an Aperture Ring it can be used with a manual TC. You will obviously need good light and a tripod but you can find the 100-300mm for fairly economical prices if you are patient and look.

Here is an example that is near me. Pentax 35 mm kit with lenses bag... Everything you need $80 and it comes with a free film body, 28-70, bag, filter and a few gadgets. You could probably sell the rest of what you get for close to the cost of the 100-300.
Hi Mistlefoot,

That's an amazing deal. I'd take it in a heartbeat but the guy won't ship.
Do I even need to bother comparing the 100-300 and the 80-320?

Wouldn't a zoom TC be just amazing? Ok, maybe not :S

I do have a 1.5x Kenko on the way. It's not the MC4 Tamron 1.4 or the likes but it should be an improvement over the Revue 2x TC.
03-26-2015, 07:16 PM   #14
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QuoteOriginally posted by Driline Quote
what did the TC cost? I bought a cheap one and it's pure crap on my DA 50-135 so I'm going to spend $450 or so on the new Pentax HD 1.4 TC.
There is a middle of the road if you'd rather not spend that much. Miscellaneous Lenses for Pentax: Teleconverters (All Brands) - Pentax Lens Review Database

The Kenko/Tamron/Vivitar Series 1 PZ-AF 1.4-1.5x are apparently all the same thing, and are available for under $200 used, and support AF even for SDM-only lenses (or HSM for Sigma). Image quality is quite good. Maybe not quite on par with the Pentax HD TC, but still quite good.
03-27-2015, 05:12 AM   #15
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I did some test shots with the Revue 2x TC on the DA*50-135 today and was not happy with the results. I'm not even going to share them.
I suppose on a sunnier day I might have somewhat better results...
back to the lab...
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