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01-14-2019, 01:32 PM   #1
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SMC Pentax-A 400mm F5.6, combine with SMC Pentax-F 1.7x AF Adapter ? On K-30

I recently bought a second hand SMC Pentax-A 400mm F5.6 prime lens, mainly for bird photography, because it seemed like a nice upgrade from the Pentax 55-300mm AF lens.
So far I've really been enjoying the challenge (the manual focussing, and increased weight) and the results are definitely a lot nicer than the 55-300 zoomlens.

By now however I'm tempted to try and get the most out of this lens by adding the SMC Pentax-F 1.7x AF Adapter to it. It makes sense to me for the following reasons:
1. It's a prime lens, so the sharpness is quite good, which makes me think it would pair well with a teleconverter. It would make it a 680mm lens, which seems awesome for bird photography
2. It would add (limited?) Auto Focus functionality to this prime lens, which could be useful, but I'm not sure how well this could work, as the adapter officialy only supports F2.8 or faster lenses. From what I've gathered it should still work reasonably well to quite well, depending on the weather circumstances.
3. The camera I would use it with is a K-30, would the full potential of this combination be reached on this camera, or does it have certain limitations?

Can anyone tell me if this combination is likely to be worth it, as the AF adapter would be relatively expensive for me to acquire? And has anyone tested the AF functionality with a Prime lens like mine?
I'm mostly interested in bird photography (both handheld and from a tripod) for now, and I'm still pretty much a beginner - this is my first SLR Camera.

Thank you in advance!

Greetings,

Michael

01-14-2019, 01:43 PM - 1 Like   #2
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Welcome aboard. I'm sure someone with an answer will be along shortly. Thanks for joining!
01-14-2019, 02:06 PM   #3
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I found it to be completely unworkable, except in bright sunlight. The ƒ9.3 maximum aperture meant even in direct sun, you couldn't count on focus confirmation. You had to manual focus without a split screen. On APS-c it was manageable with the 1.4x but just barely. Not to mention the purple fringing with that combination. I wouldn't recommend buying it just for that lens. I have the Tamron 300 2.8 and DA*200 2.8 and the 1.7 is s joy on those lenses as well as being a nice "extender" on out Tamron 90 macro and DFA 100 macro, so I do put it to good use.

I don't know if this still works but I have aside show taken with the lens.
A-400 Slideshow by Norm_Head | Photobucket

And here's one titled A-400 and 1.7x, I haven't used this account for more than a year now so my familiarity is a little suspect.
FA-1-7-TC-and-a-400 Slideshow by Norm_Head | Photobucket

In really good light with close up objects it did ok.

I actually quite enjoyed that lens. For a lens of that length the weight is excellent. I have only good memories of it, although I sold it about a year ago.

I even got a couple birds in light with it.

Last edited by normhead; 01-14-2019 at 02:17 PM.
01-14-2019, 02:25 PM   #4
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QuoteOriginally posted by normhead Quote
I found it to be completely unworkable, except in bright sunlight. The ƒ9.3 maximum aperture meant even in direct sun, you couldn't count on focus confirmation. You had to manual focus without a split screen. On APS-c it was manageable with the 1.4x but just barely. Not to mention the purple fringing with that combination. I wouldn't recommend buying it just for that lens. I have the Tamron 300 2.8 and DA*200 2.8 and the 1.7 is s joy on those lenses as well as being a nice "extender" on out Tamron 90 macro and DFA 100 macro, so I do put it to good use.

I don't know if this still works but I have aside show taken with the lens.
A-400 Slideshow by Norm_Head | Photobucket

And here's one titled A-400 and 1.7x, I haven't used this account for more than a year now so my familiarity is a little suspect.
FA-1-7-TC-and-a-400 Slideshow by Norm_Head | Photobucket

In really good light with close up objects it did ok.

I actually quite enjoyed that lens. For a lens of that length the weight is excellent. I have only good memories of it, although I sold it about a year ago.

I even got a couple birds in light with it.
Thanks for the quick and elaborate response, Normhead! I would indeed mainly be buying it for the A400mm, but the results do appear to be underwhelming .

The pictures taken without the adapter are gorgeous though! I guess I will focus on getting myself closer to the birds for now and getting more experience with the lens

01-14-2019, 03:31 PM - 1 Like   #5
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I haven't tried my copy with the Pentax-F 1.7X but it works quite nicely with a Pentax-A 1.4XL (no autofocus though).



On its own it is capable of good images, but my copy works best at F11 to eliminate purple fringing, so good light is required.










Lots more samples here.


Since I got my Pentax-DA* 300mm F4 & HD Pentax-DA 1.4x AW AF it doesn't get much use anymore.

Fred.
01-14-2019, 04:09 PM   #6
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I have used the 1.7x AF adaptor for years on the K300/4. In fact before I bought it I was able in 1991 to arrange with Pentax Canada to do a test using my PZ1 and a variety of lenses.

At that time it could easily focus any lens up to F4 but could not focus with my vivitar 400/5.6. That was then

There are a lot of people claiming it works well with the K500/4.5 but I have not tried that combo. I could get occasional focus confirmation with my tamron adaptall 200-500/5.6 and K5 but not played extensively

I don't know how my K1 MKIi will behave I hear the k5 MKIi K3 and the k1 have better low light AF but not yet tried

f5.6 is for sure a limit to me at this point
01-15-2019, 09:05 AM   #7
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Regardless of systems, I think teleconverters have their place on f/2.8 to f/4 lenses. Reason being, you typically need stop down further to achieve optimal sharpness. Case in point, I used to shoot with my Nikon 300mm f/2.8 and a 1.4x teleconverter, giving me a 420mm f/4. That said, I did not achieve optimal sharpness until I stopped down to f/5.6.

Losing 1.5 stops on a base 5.6 doesn't give that much breathing room and, as others have pointed out, limits the combination to bright lighting. Assuming you will need to stop down past f/8 to achieve optimal sharpness, could also result in shooting at a much higher ISO (lower IQ) and impact the effectiveness of the camera's AF.

With my Nikon setup, I found that cropping in post to an equivalent 420mm FOV was better than images produced with the 420mm (300mm + 1.4 TC) setup. Faster aperture means lower ISO means cleaner images. In addition, as to be expected, I found that the odds of 'keepers' increased significantly when using the bare Prime lens vs. the TC/Prime combo.

Where TC's can give an advantage, in my humble opinion, is when you shoot them stopped down to their optimal sharpness (with my setup, at f/5.6) and perform LESS cropping in post. Think of a TC as a way to FILL the frame, thus negating the use to crop as aggressively (if at all).
01-15-2019, 09:28 AM   #8
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QuoteOriginally posted by sutherland Quote
Regardless of systems, I think teleconverters have their place on f/2.8 to f/4 lenses. Reason being, you typically need stop down further to achieve optimal sharpness. Case in point, I used to shoot with my Nikon 300mm f/2.8 and a 1.4x teleconverter, giving me a 420mm f/4. That said, I did not achieve optimal sharpness until I stopped down to f/5.6.

Losing 1.5 stops on a base 5.6 doesn't give that much breathing room and, as others have pointed out, limits the combination to bright lighting. Assuming you will need to stop down past f/8 to achieve optimal sharpness, could also result in shooting at a much higher ISO (lower IQ) and impact the effectiveness of the camera's AF.

With my Nikon setup, I found that cropping in post to an equivalent 420mm FOV was better than images produced with the 420mm (300mm + 1.4 TC) setup. Faster aperture means lower ISO means cleaner images. In addition, as to be expected, I found that the odds of 'keepers' increased significantly when using the bare Prime lens vs. the TC/Prime combo.

Where TC's can give an advantage, in my humble opinion, is when you shoot them stopped down to their optimal sharpness (with my setup, at f/5.6) and perform LESS cropping in post. Think of a TC as a way to FILL the frame, thus negating the use to crop as aggressively (if at all).
My comment on this topic was written years ago. (Unfortunately it's not been read by many people.)
If you don't care to read the whole thing the basic part is "Up to a certain point, the lens without a TC will resolve all necessary detail. There then becomes a point where the lens with T.C will keep resolving the detail after it's no longer visible in the original lens. The there becomes a point where neither the original lens nor the lens with TC will resolve all necessary detail. IN the window where the original lens doesn't resolve all necessary detail but the lens with TC does, may be something like between 20-30 feet. If you believe the TC can't add detail, you haven't done sufficient testing.
Understanding folks saying a TC doesn't ad more detail. - PentaxForums.com

That a TC can't ad detail is nonsense. But it won't in every image, in fact the images where it does will probably be the exception. But, they will never make your image worse, so if you can use it, use it. Full explanation above.

Of course the above TC scenario depends on the lens out resolving the seņor but at least 40% with a 1.4 TC. I can say for sure my DA*s, the DA*60-250 ƒ4, DA* 200 2.8 and Tarmon SP AF 300 2.8 LD [IF] all have resolution to spare and to my DFA 100 macro 2.8, Tamron 90 macro, FA 50 macro and Sigma 70 macro. And all those lenses work well with the F 1.7x AF adapter as well. Consumer quality lenses are a crap shoot.

With regards to the A-400, I suspect it gets some benefit from the 1.4 in some circumstances. I don't think it has the base resolution to benefit from the F 1.7x. I'm guessing it never gets better than 1.2x if i were to hazard guess. Remember the top of the line from that era is the A*400 2.8. In the Pentax world TCs are designed for *quality lenses.


Last edited by normhead; 01-15-2019 at 09:50 AM.
01-15-2019, 09:49 AM   #9
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QuoteOriginally posted by normhead Quote
My comment on this topic was written years ago. (Unfortunately it's not been read by many people.)
If you don't care to read the whole thing the basic part is "Up to a certain point, the lens without a TC will resolve all necessary detail. There then becomes a point where the lens with T.C will keep resolving the detail after it's no longer visible in the original lens. The there becomes a point where neither the original lens nor the lens with TC will resolve all necessary detail. IN the window where the original lens doesn't resolve all necessary detail but the lens with TC does, may be something like between 20-30 feet. If you believe the TC can't add detail, you haven't done sufficient testing.
Understanding folks saying a TC doesn't ad more detail. - PentaxForums.com

That a TC can't ad detail is nonsense. But it won't in every image, in fact the images where it does will probably be the exception. But, they will never make your image worse, so if you can use it, use it. Full explanation above.
My comment wasn't in regards to whether or not a TC can capture more detail, clearly it can as the end user is exposed to more detail as a result of the magnification, it is more so to the fact that losing a stop or more in light (in order to achieve optimal sharpness) can raise ISO and, as a result, impact Image Quality. I don't see detail and image quality as necessarily being mutually exclusive, although there are times where the two can go hand in hand.

Rereading my post, I don't see any case where I stated that using a TC resulted in Less Detail, and pointed specifically to the fact that in my application, I found that where the TC got me in reach, it impacted me in image quality due to Aperture being stopped down and the ISO being higher as a result.

In optimal conditions and/or with slower subjects (where less shutter speed can be used), a TC can be a great tool.
01-15-2019, 10:01 AM   #10
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i think the whole discussion is really based upon whether you are close to filling the viewfinder with the image or not.

i used the AF adaptor for years as noted above with the K300/4, and in combination with the AF500FTZ on the *istD (note that the *istD supports TTL flash) i could get incredibly close with this combo to very small birds like chickadees etc, (less than 100mm in length) and get great images, with only a small amount of either fringing or lateral CA. see below 90% of frame crop for composition




i have done longer shots with things like herons etc, but where this combo breaks down is when the image is very far away, (consider this as equivelent to the lens on the infinity stop and the AFA focusing. in this case, it is questionabnle whether the AFA does anything to add to the quality or not.

As norm suggests, there is a range where it helps, i would suggest perhaps more than the 20-30 feet, perhaps our to 100 feet, depending on size of subject etc, but clearly no further. the subject is just too small at distances further than this to resolve any additional detail.

note that there is also some portion of luck, as i managed once to stack a sigma 2x on top of a 1.4x and achieve AF and a good shot of a whooping crane, when using a sigma APO 70-200/2.8 EX but that was a one in a million shot hand held from a boat

see below 10% of the frame from the center on a K10

01-15-2019, 10:03 AM   #11
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QuoteQuote:
QuoteOriginally posted by sutherland Quote
Rereading my post, I don't see any case where I stated that using a TC resulted in Less Detail,
Here, let me help you out.
QuoteQuote:
With my Nikon setup, I found that cropping in post to an equivalent 420mm FOV was better than images produced with the 420mm (300mm + 1.4 TC) setup.
Definitely not true with the Pentax 300 ƒ4 and 1.4 TC which is the most cost effective way to get to 420mm. Neither do people find they need to stop down to get acceptable images. ƒ5.6 is still sharpest. The issue with images beyond 5.6 with most lenses is that by ƒ8 APS_c images are diffraction limited. Although it's less pronounced with an FF like the K-1 series it's still the case.

And lower you're right about the 20-30 being to short, I didn't have tape measure out that day but I think the TC began to shine at about 60-70 feet and was good to over 100 feet.

This image taken with the Tamron 300 2.8 and 1.7 x TC (540mm ƒ4.5, I neglected to reset that FL after using the Samyang 14 2.8.) For a shot using distance of 100-150 feet, that combination produced excellent feather detail.


But compared to the A-400 that lens is 6 pounds and isn't nearly as portable. I could carry the A-400 all day. I like my Tamron 300 2.8 walks to be under 2 km even up to 5 km is OK, but, I've carried the A-400 over 10 Km without issue. I've also had situations where a friend with an 800mm equivalent bridge camera got better images than i did with the 400 and 1.7x. for a fraction the weight.

Last edited by normhead; 01-15-2019 at 10:34 AM.
01-15-2019, 10:14 AM   #12
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QuoteOriginally posted by normhead Quote
Here, let me help you out.
If you care to quote, at least do so with full context:

'With my Nikon setup, I found that cropping in post to an equivalent 420mm FOV was better than images produced with the 420mm (300mm + 1.4 TC) setup. Faster aperture means lower ISO means cleaner images. In addition, as to be expected, I found that the odds of 'keepers' increased significantly when using the bare Prime lens vs. the TC/Prime combo.'

Again, nowhere in that statement did I say that TC resulted in less detail. I said I preferred the image quality of the bare lens as it allowed me to shoot at a lower ISO as I didn't need to stop down in order to achieve the sharpness I desired.

Again, let me restate, my case is due to higher ISO as a result of stopped down aperture vs. cropping with a lower ISO captured image. That doesn't imply less detail or more detail. It just spoke to the image quality I obtained as of result ISO from shooting stopped down.

I did not say less detail and I am not saying that a teleconverter should be avoided.
01-15-2019, 10:28 AM   #13
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QuoteOriginally posted by sutherland Quote
If you care to quote, at least do so with full context:

'With my Nikon setup, I found that cropping in post to an equivalent 420mm FOV was better than images produced with the 420mm (300mm + 1.4 TC) setup. Faster aperture means lower ISO means cleaner images. In addition, as to be expected, I found that the odds of 'keepers' increased significantly when using the bare Prime lens vs. the TC/Prime combo.'

Again, nowhere in that statement did I say that TC resulted in less detail. I said I preferred the image quality of the bare lens as it allowed me to shoot at a lower ISO as I didn't need to stop down in order to achieve the sharpness I desired.

Again, let me restate, my case is due to higher ISO as a result of stopped down aperture vs. cropping with a lower ISO captured image. That doesn't imply less detail or more detail. It just spoke to the image quality I obtained as of result ISO from shooting stopped down.

I did not say less detail and I am not saying that a teleconverter should be avoided.
Wow.... whatever. You posted, I felt i needed to clarify. You feel I didn't need to clarify. I guess I'm just not smart enough to understand the nuances of your phrasing. There may be others in the same boat.

I guess the main problem with your post is the referred to scenario where higher IQ ruins an image, isn't a given. My photo above was taken at 1600 ISO. There are lots of scenarios where shooting wide open with high ISO is just fine. Another thing you neglected to mention.

Last edited by normhead; 01-15-2019 at 10:39 AM.
01-15-2019, 11:04 AM   #14
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QuoteOriginally posted by normhead Quote
Wow.... whatever. You posted, I felt i needed to clarify. You feel I didn't need to clarify. I guess I'm just not smart enough to understand the nuances of your phrasing. There may be others in the same boat.

I guess the main problem with your post is the referred to scenario where higher IQ ruins an image, isn't a given. My photo above was taken at 1600 ISO. There are lots of scenarios where shooting wide open with high ISO is just fine. Another thing you neglected to mention.
Totally fair and appreciate the conversation. Perhaps you didn't understand, perhaps I poorly communicated, it's all water under the bridge at this point and not worth bickering over.
01-15-2019, 11:26 AM   #15
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i see some comments about not using a TC because it allows you to use lower iso, i would suggest this is a double edged sword. you need to consider for acceptable sharpness, when you crop tighter than full frame, the circle of confusion gets smaller to offset the higher enlargement from the sensor, while for relatively large subjects this can sometimes be OK, in many cases it is not, i would prefer to get the image as big as possible, pushing the histogram a little to the right, and getting as high a shutter speed as possible,

for me grain is much preferred to lack of sharpness due to shake and over enlargement of a tiny image
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