After doing some testing of the new Pentax converter with my Pentax K-3 and DA*300 and also my Kenko 1.5x converter i find that the Kenko has better IQ and is a little wider than the Pentax even though it is 1.5x for the Kenko and 1.4x for the Pentax. The not so good IQ bothers me but at the same time the Pentax is correcting the f-stop and focal length and is AW. It is not much but visible. Someone also suggested to put both of them on the camera but the AF still hunts with the Kenko on the DA*300.

Thoughts?

[vonBaloney]

After doing some testing of the new Pentax converter with my Pentax K-3 and DA*300 and also my Kenko 1.5x converter i find that the Kenko has better IQ and is a little wider than the Pentax even though it is 1.5x for the Kenko and 1.4x for the Pentax. The not so good IQ bothers me but at the same time the Pentax is correcting the f-stop and focal length and is AW. It is not much but visible. Someone also suggested to put both of them on the camera but the AF still hunts with the Kenko on the DA*300.

Thoughts?

I think the "1.5x" on the Kenko is just a plain lie -- it is exactly the same TC as the Tamron-F 1.4x Pz-AF, but with different coatings. (I think -- comparing the Kenko and Tamron side-by-side I got identical images in terms of FOV and overall quality, but the color casts were noticeably different. Could also just a be a difference in when they were made I suppose.)

It is a bit surprising if it beats out the new Pentax, but the Tamron/Kenko has always been an excellent TC.

[dc1500]

I have the Kenko and have found IQ pretty good on the DA*300 but was expecting the Pentax to at least match it. As you say, my Kenko hunts and is hit or miss on AF. Is the Pentax much better in that respect?

[vonBaloney]

I have the Kenko and have found IQ pretty good on the DA*300 but was expecting the Pentax to at least match it. As you say, my Kenko hunts and is hit or miss on AF. Is the Pentax much better in that respect?

Well, your DA*300 will be an f/5.6 with the TC, and on models prior to the K-5II anyway, that is slow enough that it will often hunt if not in bright daylight (at anything above 6.3 AF is hopeless in general). I would expect the new TC to be just the same in that regard.

The Pentax TC does not hunt. The AF is as good as without.

Also if I stop down one stop on both to compare the Pentax IQ becomes as good as the Kenko.

I also did a test where I took a picture from the exact same place, just adding the TC, and then upsampled the one without the TC to 140% and cropped it and these are my findings.

First one upsampled, second with TC.

---------- Post added 03-22-14 at 11:21 AM ----------

I can not see that the TC adds any detail. Am I doing this wrong?

I have done some more testing on far away objects and found the same fenomenon. The optical increase in detail with the new Pentax TC is less than upsampling the DA*300+K-3 kombo. This is really a disappointment...

The picture becomes soft which locks like bad focus but I have manually focused in LV with enlargment and used timed shutter release.

[normhead]

I got the exact opposite results, perhaps something is wrong with your TC,

I got the exact opposite results, perhaps something is wrong with your TC,

And you are using the same combo? K-3, DA*300 and TC.

[mgvh]

I have the Kenko Pz-AF 1.5X Teleplus SHQ which provides about 1.4x and is apparently the same as the Tamron 1.4x. I also have a cheap Focal MC 2x (with contacts for metering). I have tried both of these on different lenses, and compared them with upsampled images w/out a TC. I don't have any stellar lenses at the longer end, my best probably being a Tamron 90mm. (Others: DAL 55-300; Tak bayonet 135; TeleTak 200 f5.6; Soligor 250 f4.5; Five Star 500mm f8)

a) For some lenses, not using a TC and upsampling is just as good or better.
b) For some lenses, the Kenko is better.
c) For a few lenses, the Focal is better.
d) It seems to make a difference whether I'm shooting something close (say 25-50 feet) as compared to distant (100+ feet).

I've made enough attempts to try to minimize the effects of my focusing attempts, but the best I've come up with is to make a list for myself of what to use in a particular combination of lens/TC/distance.

Maybe there is some physics involved in the interaction of those factors. In any case, I'm finding it hard to make a general statement about the use of TCs.

In the end, for maximum telephoto w/ the gear I have, the Five Star 500m w/ the Kenko TC provides best results. (But I'm still dreaming about the DA 300...)

[vonBaloney]

Close focusing of long telephoto lenses often introduces more aberrations so I'd assume you'd have best luck using the base lens at distances where it excels. The above pics are surprising though -- the TC is clearly softer, and quite noticeable on the edges. But I also see the shutter speeds are long (and twice as long with the TC, naturally), so vibration is also a possibility.

[normhead]

And you are using the same combo? K-3, DA*300 and TC.

I'm using the DA*60-250... but, the Pentax TC has increased subject resolution with every lens I've tried it on. But then, I haven't tried it on any of my weaker lenses. Surely the DA*300 doesn't fall into that category.

From my own test, posted on this page.
https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/253807-tele...shipped-3.html

The scene shot at 250mm.


The test chart, cropped to the size of the chart @250mm.


The test chart, cropped to the size of the chart @350mm. DA*60-250 + 1.4


The test chart, cropped to the size of the chart @400 mm (A-400)


The test chart, cropped to the size of the chart @450mm. DA* 60-250 + F 1.7 TC


The test chart, cropped to the size of the chart @560 mm (A-400 +1.4 TC)


The trend seems to be a constant improvement with longer focal length. No apparent degradation of the image due to TC use. IN this series the A-400 came out better than the DA*60-250 with the 1.4. I might have to devise a tie break.

I can't comment on other TCs I don't own them, but I really haven't found a lens my Pentax 1.4 doesn't work well with.

[awaldram]

I also did a test where I took a picture from the exact same place, just adding the TC, and then upsampled the one without the TC to 140% and cropped it and these are my findings.

First one upsampled, second with TC.

---------- Post added 03-22-14 at 11:21 AM ----------

I can not see that the TC adds any detail. Am I doing this wrong?

Given your examples it apears your camera is only just inside the DoF with the da*300+HD converter

As this is visible at close focus it will deteriate further for distance.

Have you by chance calibrated you lens at close distances as this will almost certainly be wrong if you were closer then 50M.?

For 300mm ideally more than 75M

and for 300mm+converter 105M

Close focusing of long telephoto lenses often introduces more aberrations so I'd assume you'd have best luck using the base lens at distances where it excels. The above pics are surprising though -- the TC is clearly softer, and quite noticeable on the edges. But I also see the shutter speeds are long (and twice as long with the TC, naturally), so vibration is also a possibility.

The shutter speeds are long but it is on a sturdy tripod indoors and I have used MUP. It is not camera shake.


I have tried the combo at longer distance, 25 yards, and found the same but I will test to see if there is some micro adjustment that has to be done...

---------- Post added 03-22-14 at 06:46 PM ----------

Given your examples it apears your camera is only just inside the DoF with the da*300+HD converter

As this is visible at close focus it will deteriate further for distance.

Have you by chance calibrated you lens at close distances as this will almost certainly be wrong if you were closer then 50M.?

For 300mm ideally more than 75M

and for 300mm+converter 105M

I tested calibrating indoors at close range and it does have an effect. I found that the camera sees the adjustment differently with or without the TC so one can calibrate lens and lens+TC separately.

I have no adjustment on the lens. +-0. With the combo indoors it needs +10. Longer distance seems to not wanting this +10. Maybe a minus then... It was +-0 when doing the shots you have not seen due to the fact that I cant upload them...

Tomorrow I will test on a normal using distance.

[awaldram]

The shutter speeds are long but it is on a sturdy tripod indoors and I have used MUP. It is not camera shake.


I have tried the combo at longer distance, 25 yards, and found the same but I will test to see if there is some micro adjustment that has to be done...

---------- Post added 03-22-14 at 06:46 PM ----------



I tested calibrating indoors at close range and it does have an effect. I found that the camera sees the adjustment differently with or without the TC so one can calibrate lens and lens+TC separately.

I have no adjustment on the lens. +-0. With the combo indoors it needs +10. Longer distance seems to not wanting this +10. Maybe a minus then... It was +-0 when doing the shots you have not seen due to the fact that I cant upload them...

Tomorrow I will test on a normal using distance.

Any lens should be calbrated at between 25 and 50 times its focal length anything else will lead to surprising and disapointing results.