pentax 300mm f4 with 1.4 or 2x teleconverter possible ?

Curious if this lens is able to work with 2x teleconverter giving an F8 at 600mm ?

Anybody extend the zoom of this lens.

Jay

JayDog said:

Curious if this lens is able to work with 2x teleconverter giving an F8 at 600mm ?

Anybody extend the zoom of this lens.

Click to expand...

I've seen plenty of reports of the DA* 300mm f/4 being used with the Pentax DA 1.4x Rear Converter. I've done it myself, with satisfactory results.

I don't recall any reports of using it with a 2x teleconverter. Once it gets to f/8, I would start to expect AF problems.

This is taken with the K70, DA*300 plus the Pentax HD 1.4 converter plus the image is about 50% cropped. (with my copy of the 300mm AF is very slow) I had in the past a kenko 2X converter but image quality was better cropping then using that converter.

--
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I have used my DA* 300mm with the Pentax 1.7x and it performs well although there are the usual AF restrictions due to how the adapter works.

Mike, the 1.7x hard to find ?

Jay

Nowadays most new AFA x1.7 are coming from Japan, at least on $bay. I guess you can find new items from old stock in some countries depending on where you live. Otherwise you can find some second hand from time to time.

It's nice to have if you want AF with old A lenses (only center point and prefocused). At least it works fine with A* primes.

Regards, Fred

Works excellently with the old AFA 1.7x, giving you a 50mm f/6.7 or so. It does take a little practice to get the hang of manual/auto focus, but once you get it its pretty quick.

Here's a polar bear in Svalbard.

This pic scares the living bejeezus out of me.

You are still far too close!

Well done, though.

AB

I took the polar bear photo from a Zodiac out in the ocean just off the gravel bar the bear was walking on. Would not have been that close on land, at least not on purpose!

PS: Obviously typing too fast when I posted the photo. It's "500mm."

Real nice photo. /

Is it hard to get the 1.7x converter now a days ?

Expensive ? I think i seen the 1.4 at like a wopping 569????

Last time I saw the 1.7x at KEH I think it was around $300. They come up now and again.

Here's another, with the 1.7x converter on the KP. Note it's at fairly high ISO, 6400.

Hi there, I have the HD DA 1.4x TC and recently bought two higher powered TCs to get a greater focal length for photographing small birds I've added a 1.7x Promaster (4 elements) and a Tamron 2x MC7 (7 elements).

I started out with the DA*300 but because neither of the two TCs (1.7x and 2x) will auto focus with the DA*300 despite having SDM contacts meaning manual focus - unsuitable because it is too slow and imprecise for photographing the small fast moving New Zealand forest birds, I've bought the film era FA* 300 f4.5 that works very quickly with the K1's excellent AF motor.

Image quality with the DA*300?
Not too bad at all with the Tamron 2x and very good with the Promaster 1.7x see te two images below that are pushed up to 50% in Photoshop then the field of view cropped. This is what you see in the images.

The hairs on the body of Monarch butterflies is well defined with the Promaster 1.7x and the joints of one antenna are clear to see in the original file.

The Tamron surprised me as it too as the body hairs are visible and you can see the joints in the antennae. The Tamron 2x images were slightly coarser than the Promaster 1.7x - as you'probably expect but for photographing small birds that are 2-3 times the length of a Monarch there is plenty of fine feather detail shown.

Another surprise was using the FA* 300 f4.5 . I suspect it is slightly sharper than the DA*300, the only drawback is the 1/3 stop slower that makes itself felt in the dim light under our forest canopy by pushing up the ISO higher so noise becomes an issue.

First image: DA*300 plus Tamron 2x TC:





Second image: DA*300 plus Promaster 1.7x TC:

So I take it the 1.7 on the 300 is manual focus ?

That said, the iso at 6400 is very controlled.

Jared

MikePursey said:

I have used my DA* 300mm with the Pentax 1.7x and it performs well although there are the usual AF restrictions due to how the adapter works.

Click to expand...

I have tried the 1.7x AFA on my 300, and the modern 1.4x converter is much sharper. It works almost perfectly with the DA* 300/4, as it was designed specifically to work with that lens in particular, along with the DA* 200/2.8 and the DA* 60-250/4. According to my tests, with a 24MP sensor, the combination of 300/4 and 1.4x converter is, under the best conditions, sharper than magnifying without conversion. This implies that the pair can make full use of the 3.9 micron photosite pitch of that sensor. Most long lenses don't do so.

--
"A good photograph is knowing where to stand." -- Ansel

paulkienitz said:

I have tried the 1.7x AFA on my 300, and the modern 1.4x converter is much sharper. It works almost perfectly with the DA* 300/4, as it was designed specifically to work with that lens in particular, along with the DA* 200/2.8 and the DA* 60-250/4. According to my tests, with a 24MP sensor, the combination of 300/4 and 1.4x converter is, under the best conditions, sharper than magnifying without conversion. This implies that the pair can make full use of the 3.9 micron photosite pitch of that sensor. Most long lenses don't do so.

Click to expand...

Sigh ... this is why I don't post much in this forum (or any other for that matter).

Nowhere did I say the 1.7x was sharper than the 1.4x (which I also have). The OP was asking about 1.4x and 2x teleconverters so I gave him another option which will give him a longer focal length at a cheaper price than the 1.4x.

Mike thanks for the reply. You helped me out.

The AFA 1.7 converter is a relic of film days. It was designed to give autofocus to manual-focus lenses. To use it, the photographer roughly manual focuses the image. Once it's close, the converter can fine tune the focus precisely.

MikePursey said:

paulkienitz said:

I have tried the 1.7x AFA on my 300, and the modern 1.4x converter is much sharper. It works almost perfectly with the DA* 300/4, as it was designed specifically to work with that lens in particular, along with the DA* 200/2.8 and the DA* 60-250/4. According to my tests, with a 24MP sensor, the combination of 300/4 and 1.4x converter is, under the best conditions, sharper than magnifying without conversion. This implies that the pair can make full use of the 3.9 micron photosite pitch of that sensor. Most long lenses don't do so.

Click to expand...

Sigh ... this is why I don't post much in this forum (or any other for that matter).

Nowhere did I say the 1.7x was sharper than the 1.4x (which I also have). The OP was asking about 1.4x and 2x teleconverters so I gave him another option which will give him a longer focal length at a cheaper price than the 1.4x.

Click to expand...

Sorry, I didn't mean that to come across as undercutting your post -- I was mainly speaking to the OP, giving reasons why I would recommend the 1.4x over the 1.7x.