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02-27-2010, 08:13 AM   #1
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Pentax F-1.7X AF adapter: input focal length or not?

So, I finally got this 1.7X adapter and it seems to work well from what I have tried this morning.

I use a DA*300/4 on my K7 for the "tests"; the camera is left on AF-S and the lens is left on AF.

Because I had to input the focal length after turning the camera on, I thought that was a bit weird, so I searched and found this:
https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/19118-pentax-s...s-adapter.html

Questions:
No. 1:
If I leave the SR on while turning the camera on, it will show the "input focal length" display on the rear LCD screen; if I choose to do that because I want to retain the SR, what exactly would be the focal length to enter? Do I have to input 300mm or the actual TC+lens focal length which would then be 510mm?
I took one test pic and it seems to be OK with a 300mm input, the SR was ON and the review screen shows me F6.7 and 300mm. Normal this far if I take into consideration that the camera just doesn't care about entering the REAL total focal length. Right? Wrong?
The resulting image is quite right on focus (short distance, inside, handheld with good lighting)
EDIT: Just tried it again, but this time entering a 500mm focal length input. I don't know if it's me, but this picture was actually in sharper focus than at a 300mm input.

No.2:
I turn the camera ON, input 300mm, and then turn the SR off; Turn the camera on again and it won't show me the focal length input screen this time -- all normal according to the linked thread above.
I take a pic and look at the reviews and it shows me F---, and 300mm.
The picture looks OK here too. Focus is as good as in the first test above.

Any reply would be welcome as I am going out this afternoon to test this, hopefully on some gulls nearby .... if they haven't been scared off by the snow storm we got yesterday!

Cheers.

JP


Last edited by jpzk; 02-27-2010 at 08:20 AM. Reason: Added information
02-27-2010, 09:15 AM   #2
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With my F* 300mm f4.5 I set it to 500mm .. same as with my A* 300mm f2.8.

I may be doing it wrong but I would presume that as the TC changes the Exif correctly it would also do so with the focal length if it were compensating for it.
02-27-2010, 09:53 AM   #3
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QuoteOriginally posted by Mike.P® Quote
With my F* 300mm f4.5 I set it to 500mm .. same as with my A* 300mm f2.8.

I may be doing it wrong.
You're doing it wrong.
02-27-2010, 10:41 AM   #4
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The 1.7x afa will change the f stops in the exif but I always put 500mm in when I turned on the camera. I think you will be very pleased with the result with the DA 300mm (I was)

02-27-2010, 10:45 AM   #5
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QuoteOriginally posted by dragonfly Quote
You're doing it wrong.
No he's not
02-27-2010, 12:33 PM   #6
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I am back with testing the DA*300/4 with the 1.7X Pentax adapter and it does work rather well.
I will be posting some pics in My Albums as soon as I am done with a few chores here.

So, to summarize, I tried both, entering the 300 and 500mm input, and the results are quite similar, but slightly more focused at 500mm!
That also gave me a F6.7 max aperture at ISO1000-1250.
I had to compensate at +0.7 and I think one was up to +1.0.
I find that the image in the viewfinder was slightly darker but you have to keep in mind that today was a very bleak day, overcast with tons of humidity coming off the freshly fallen snow from yesterday's storm.

The focus was very quick too, as long as you pre-focus a bit before the TC engages.
Overall very pleased with the results and I can't hardly wait until we get a sunny day. That should make a world of difference.

So, back soon ... tonight or tomorrow with pics.

JP
02-27-2010, 12:56 PM   #7
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Here's a sample from when I had the DA300 and 1.7x, a 100% crop of a wild Eagle at f8, 1/3 stop from wide open(I think). I think I used a monopod and SR (500mm). A very nice combo when you have good light.


Last edited by borno; 02-27-2010 at 06:20 PM.
02-27-2010, 04:11 PM   #8
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F* 300mm f4.5 and 1.7x. Hand held.



02-27-2010, 06:09 PM   #9
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Someone needs to tire of their Pentax 1.7x because I feel the need! As the new owner of a A*400/2.8 and both 1.4xL and 2xL Rear Converters, I think I would prefer just the one Converter...the 1.7x. Not so much for the AF but for the range.

So, who is going to tire of their's first? Please make sure you want some of my stuff in trade.

But I actually have a real question about the 1.7x.
Has anybody been able to do an IQ test against the 1.4xL and 2xL? or even a 3rd party like the Tammy 1.4x Pz MC4?

edit- another vote for using the calculated FL and not the lens FL if you have to input the number. That is one of the advantages of the Pentax 1.7x I once read.
02-27-2010, 07:50 PM   #10
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The object of putting the focal length into the SR system when the camera does not recognize the focal length of the lens is to tell the camera the amount of angular velocity to expect when compensating. However you get to 500mm +/-, you need to tell the camera that the effective focal length for SR is 500. eg. 250+2x, 300+1.7x, 360mm + 1.4x, whatever you are using.
02-27-2010, 09:34 PM   #11
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QuoteOriginally posted by borno Quote
Here's a sample from when I had the DA300 and 1.7x, a 100% crop of a wild Eagle at f8, 1/3 stop from wide open(I think). I think I used a monopod and SR (500mm). A very nice combo when you have good light.
Great shot!
I would assume that you ended up with a F-stop of 6.7 or so with this lens plus the TC?
Yes, good light is a must, although I did get some acceptable shots today with a terribly overcast and humid day, at ISO 1250.

JP
02-27-2010, 09:35 PM   #12
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QuoteOriginally posted by Mike.P® Quote
F* 300mm f4.5 and 1.7x. Hand held.
Great shot too!
With this combo, what was your resulting focal length?

JP
02-27-2010, 09:45 PM   #13
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QuoteOriginally posted by imtheguy Quote
Someone needs to tire of their Pentax 1.7x because I feel the need! As the new owner of a A*400/2.8 and both 1.4xL and 2xL Rear Converters, I think I would prefer just the one Converter...the 1.7x. Not so much for the AF but for the range.

So, who is going to tire of their's first? Please make sure you want some of my stuff in trade.

But I actually have a real question about the 1.7x.
Has anybody been able to do an IQ test against the 1.4xL and 2xL? or even a 3rd party like the Tammy 1.4x Pz MC4?

edit- another vote for using the calculated FL and not the lens FL if you have to input the number. That is one of the advantages of the Pentax 1.7x I once read.
You should post a "Wanted" ad in the Market Place.
That is how someone got hold of me and offer his.
I just got mine recently ... not much chance to part with it
Oh! I forgot: you may have a FA*400/5.6 for sale?

I haven't seen any IQ tests, as you suggest but it would be nice to know what the results would be. I have made a few searches, to no avail.

Yes, I found that when the camera asks for focal length input, using the DA*300/4, entering 500 (should be 510mm actually) worked better than letting the camera calculating it.
That TC should work well with this monster you just bought! I hope you can find one soon, but beware of those eBay sales where I saw this TC selling for 900$ !!!

JP

Last edited by jpzk; 02-27-2010 at 09:50 PM.
02-28-2010, 02:05 AM   #14
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I can do a few tests once the weather clears up here.

I have the A* 300mm f2.8 with 1.4x and 2x-L converters as well as the 1,7x.
Can't help with the Tamron 1.4x as I sold it last week, just didn't rate it against the 1.7x.
02-28-2010, 09:15 AM   #15
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QuoteOriginally posted by jpzk Quote
You should post a "Wanted" ad in the Market Place.
You're right. I just know I shouldn't spend anymore right now. At least until I know if its a step up, down or just sideways from the 3 converters I own.

QuoteOriginally posted by jpzk Quote
That TC should work well with this monster you just bought! I hope you can find one soon, but beware of those eBay sales where I saw this TC selling for 900$ !!!
I try not to look at ebay listings. I only bought the A*400/2.8 from ebay because a Forum member started a thread about the listing. I will save my $$ and wait for yours.




QuoteOriginally posted by Mike.P® Quote
I can do a few tests once the weather clears up here.

I have the A* 300mm f2.8 with 1.4x and 2x-L converters as well as the 1,7x.
Can't help with the Tamron 1.4x as I sold it last week, just didn't rate it against the 1.7x.
That would be great. I did some very loose testing of the 1.4xL against the Tammy 1.4x and didn't see any significant difference just based on a handfull of snaps. Your testing will spur me to do it again with a little purpose in mind and some difficult conditions
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