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05-05-2009, 01:39 PM   #31
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QuoteOriginally posted by OldNick Quote
PMFJI

Has anyone compared the shots with and without TCON, in any combination, by taking the same shot with and without, then zooming the Tcon shot to, say 100% and the non-Tcon to 140%, and seeing whether there is actually a gain? I am not in the big league (yet), but I bought a 1.4X Raynox TCon for my bridge camera, and that was the only real test that counted AFAICS. I found that in my case, it was not worth using the TCon. There was no gain over simply cropping.

While that was all done at the lower end of the pool, I feel it still applies.
If you crop a 10 megapixal image so that is magnified by 2x, would you have a 5megapixal image, the pixals being twice the size? If you use a 2x converter do you have the same magnified image but still have 10megapixals?

05-05-2009, 01:46 PM   #32
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QuoteOriginally posted by Radar Quote
If you crop a 10 megapixal image so that is magnified by 2x, would you have a 5megapixal image, the pixals being twice the size? If you use a 2x converter do you have the same magnified image but still have 10megapixals?
No, Radar, you would actually have a 2.5 Mp image. The converter 2x is linear, not based on the area. With the converter, you still have a 10 Mp image. The problems using a TC are
  • 2x = 2x the aperture as well. f/5.6 becomes f/11, needing 4 times the shutter speed for the same exposure (or 4 times the ISO, or 2x Tv and 2x ISO)
  • Every one of the flaws in the lens are magnified by 2x, including chromatic aberration and the dreaded purple fringe.
  • Along with the 2x larger image comes 2x the shake. So you need an even higher shutter speed, but the new aperture prevents that, unless you increase the ISO beyond belief and start to get noise.
It basically boils down to TANSTAFL.*

Albert in the Rockies.

*There ain't no such thing as a free lunch" - attributed to Robert A. Heinlein.
05-05-2009, 03:21 PM   #33
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The words Albert speaks are true. I would also add that you are adding more glass, and that's never good, unless it's done specifically to fix other pieces of glass.

So your IQ will also be hurt by the TCon. IT may in fact magnify stuff _more_ than it magnifies the image, especially softness.

It's no good putting a cheap TCon on a really sweet lens, and vice versa.

This is why I am wondering if anyone has ever done the test I suggested, with one or more TCons.
05-05-2009, 03:40 PM   #34
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QuoteOriginally posted by G_Money Quote
Pentax 1.7 AF Converter

I posted this link in another thread, but I'll repeat it here too. It seems that jinfinance, seller of eBay split-prism focus screens, sells these converters brand new on eBay. While I've read elsewhere that these are out of production, it appears that this seller has access to a cache of NOS converters.

I checked his store & it says he has 124 of them in stock. Can that be believed?

05-05-2009, 03:45 PM   #35
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I'll start saving - if he's still got some in a year i'll be have one
05-05-2009, 05:01 PM   #36
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QuoteOriginally posted by blind-bat Quote
I checked his store & it says he has 124 of them in stock. Can that be believed?
I don't see where it says that, when I look all I see is "more than 10 available". Mine arrived in the mail yesterday and as he says, it's brand new. Works nicely with the DA*300. When powering up the camera asks for focal length (unlike the Tamron and Promaster) so SR should be a little more accurate. Just for the hell of it, I put it behind the Lester Dine. It seemed unnatural to have that lens focus itself, not that I'll ever use them together. If Pentax would just get off their arses and cobble up an SDM compatible converter it would make matters so much easier.

One funny thing I noticed is that the DA*300 and the Promaster 1.7X TC only achieve focus under optimal conditions (bright light, contrasty subject), but the same TC when paired with the DA 55-300 (@300mm) consistently hits focus even though it's more than a full stop slower than the DA*.

Is there such a thing as TCBA?
05-05-2009, 05:04 PM   #37
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QuoteOriginally posted by G_Money Quote
I don't see where it says that, when I look all I see is "more than 10 available". Mine arrived in the mail yesterday and as he says, it's brand new. Works nicely with the DA*300. When powering up the camera asks for focal length (unlike the Tamron and Promaster) so SR should be a little more accurate. Just for the hell of it, I put it behind the Lester Dine. It seemed unnatural to have that lens focus itself, not that I'll ever use them together. If Pentax would just get off their arses and cobble up an SDM compatible converter it would make matters so much easier.

One funny thing I noticed is that the DA*300 and the Promaster 1.7X TC only achieve focus under optimal conditions (bright light, contrasty subject), but the same TC when paired with the DA 55-300 (@300mm) consistently hits focus even though it's more than a full stop slower than the DA*.

Is there such a thing as TCBA?
I have it in my list of items being watched & when it's in the list format it says 124 available. Funny that when I click on the item, it only shows 10 remaining.
05-05-2009, 05:41 PM   #38
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QuoteOriginally posted by G_Money Quote
I don't see where it says that, when I look all I see is "more than 10 available". Mine arrived in the mail yesterday and as he says, it's brand new. Works nicely with the DA*300. When powering up the camera asks for focal length (unlike the Tamron and Promaster) so SR should be a little more accurate. Just for the hell of it, I put it behind the Lester Dine. It seemed unnatural to have that lens focus itself, not that I'll ever use them together. If Pentax would just get off their arses and cobble up an SDM compatible converter it would make matters so much easier.

One funny thing I noticed is that the DA*300 and the Promaster 1.7X TC only achieve focus under optimal conditions (bright light, contrasty subject), but the same TC when paired with the DA 55-300 (@300mm) consistently hits focus even though it's more than a full stop slower than the DA*.

Is there such a thing as TCBA?
I did not know that the Promaster AF 1.7x will work on SDM for AF. I don't recall others reporting the promaster 1.7x TC work with SDM lens. The promaster 1.7x work with my Tamron 70-300mm with f/5.6 in the 300mm and I won't be surprised that it works with Pentax 55-300mm in the 300mm end.

As for Pentax-F 1.7x AFA, if it is priced close to $300, it is well worth the money. It is one of my most valuable and most used TC working with both MF and AF lens. I have not used it on my SDM lens with DA* 50-135mm as I don't yet see the need. I intend only to use TC to reach over 300mm. But when I used it on manual lens in K mount and M42 mount, it get pretty reasonable results and with the magical AF transformation for manual focusing lenses.

One nice thing about the Pentax-F 1.7x AFA is that it treats your lens as MF lens and you can enter SR focal length. This is unlike all other current AF TC that will leave the SR focal length unchanged. It will be less complicated when the SDM TC come out, but until that happen, I treat my Pentax-F 1.7x AFA as my go-to and special TC. Even when the future version of SDM TC come out, the AFA is still the only TC that can transform a MF lens into AF.


Pentax F* 300mm f/4.5 + Pentax-F 1.7x AFA






Thanks,
Hin


Last edited by hinman; 05-05-2009 at 05:56 PM.
05-05-2009, 05:46 PM   #39
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Gees I have one of those Pentax SMX 1.7x AF Teleconvertors. I never use it and have been thinking of selling it.

I might have to sell it I think
05-05-2009, 06:03 PM   #40
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OK. Sorry I said anything. PMFJO again
05-05-2009, 06:40 PM   #41
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QuoteOriginally posted by hinman Quote
I did not know that the Promaster AF 1.7x will work on SDM for AF. I don't recall others reporting the promaster 1.7x TC work with SDM lens. The promaster 1.7x work with my Tamron 70-300mm with f/5.6 in the 300mm and I won't be surprised that it works with Pentax 55-300mm in the 300mm end.

As for Pentax-F 1.7x AFA, if it is priced close to $300, it is well worth the money. It is one of my most valuable and most used TC working with both MF and AF lens. I have not used it on my SDM lens with DA* 50-135mm as I don't yet see the need. I intend only to use TC to reach over 300mm. But when I used it on manual lens in K mount and M42 mount, it get pretty reasonable results and with the magical AF transformation for manual focusing lenses.

One nice thing about the Pentax-F 1.7x AFA is that it treats your lens as MF lens and you can enter SR focal length. This is unlike all other current AF TC that will leave the SR focal length unchanged. It will be less complicated when the SDM TC come out, but until that happen, I treat my Pentax-F 1.7x AFA as my go-to and special TC. Even when the future version of SDM TC come out, the AFA is still the only TC that can transform a MF lens into AF.
Forum member danielchtong reported that the Promaster 1.7 worked with SDM, and since it was the most reasonably priced I opted to try it. Like you, I only intend to use a TC to extend my reach past 300mm. I'm just surprised that the Promaster focuses more consistently with the dimmer 55-300 zoom. And the mechanicals of the Tamron and Promaster (except for the optics, of course) are identical, somewhat surprising to me. I sure would like to know when we can expect that Pentax SDM TC, though. 510mm is the longest focal length I've ever shot with, and I need all the SR help I can get. For the time being I seem to do better handheld than with a monopod, but my monopod technique is woefully lacking. Will practise more this weekend.

BTW, Hin, it was your old Lester Dine to which I affixed the Pentax AF!

05-05-2009, 07:25 PM   #42
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QuoteOriginally posted by G_Money Quote
Forum member danielchtong reported that the Promaster 1.7 worked with SDM, and since it was the most reasonably priced I opted to try it. Like you, I only intend to use a TC to extend my reach past 300mm. I'm just surprised that the Promaster focuses more consistently with the dimmer 55-300 zoom. And the mechanicals of the Tamron and Promaster (except for the optics, of course) are identical, somewhat surprising to me. I sure would like to know when we can expect that Pentax SDM TC, though. 510mm is the longest focal length I've ever shot with, and I need all the SR help I can get. For the time being I seem to do better handheld than with a monopod, but my monopod technique is woefully lacking. Will practise more this weekend.

BTW, Hin, it was your old Lester Dine to which I affixed the Pentax AF!

http://img.photobucket.com/albums/v135/G_Money/_IGP1194.jpg
My friend, you are killing me with a shot like that. I disliked the Lester A Dine Marco lens for some reasons. I am perhaps the tiny few minority who doesn't like the Lester A Dine. It must be me who doesn't use it correctly, especially in 1:1.

I sold my Promaster 1.7x for $65.00 way too early. I should have kept it. Somehow, that Promaster serves me better in PF/CA when compared to Tamron 1.4x TC. But my all-time favorite TC is still the Pentax-F 1.7x AFA

Thanks,
Hin

Last edited by hinman; 05-06-2009 at 01:30 PM.
05-05-2009, 09:39 PM   #43
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Just an update. I have put my Pentax AF 1.7x adaptor in the marketplace. $350AUD that about 170pound and I will ship international.

https://www.pentaxforums.com/forums/photographers-marketplace/59328-sale-pent...convertor.html
05-06-2009, 11:47 AM   #44
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QuoteOriginally posted by Canada_Rockies Quote
...

*There ain't no such thing as a free lunch" - attributed to Robert A. Heinlein.
Now, that brings back some old memories .
05-06-2009, 01:18 PM   #45
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QuoteOriginally posted by Bart Quote
Now, that brings back some old memories .
Hey, Bart - it is a really true statement, though.
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