[luftfluss]

On a camera like the K-1, I would think there's enough resolution with that sensor normally (never mind via PixelShift) that cropping would be preferable to use of a TC.

A sharp lens coupled with a good TC will still give you a resolution advantage compared with cropping, even taking into account having to using a higher ISO to counter the loss of light.

Use of a TC can also help improve AF acquisition, because the subject is that much larger in the focus area. For example, photographers occasionally struggle to photograph swimming birds, because the camera will sometimes focus on the bird's reflection in the water rather than the bird itself. A teleconverter can make the bird appear large enough that the camera has more to focus on and the AF is less confused by the reflection. Also, easier for the photographer to track a moving subject.

Tangentially related to photography, having the subject appear larger in the VF can also make it easier to observe the animal's behavior, which I enjoy just as much as the actual picture-making.

A lower-quality lens coupled with a TC is probably worse than simply cropping.

Edit: I should also add, if you use manual-focus lenses, a TC can really help with focus acquisition.

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Last edited by luftfluss; 01-03-2023 at 08:55 AM.

[normhead]

Tangentially related to photography, having the subject appear larger in the VF can also make it easier to observe the animal's behavior, which I enjoy just as much as the actual picture-making.

No kidding, I've seen lots of stuff I'll probably never capture. Sort of like under-powered binoculars.

A lower-quality lens coupled with a TC is probably worse than simply cropping.

I have one lens, an older Vivitar 135 2.8 K-mount, probably from the 70s or 80s that meets that definition. It cost us $30. I'd be happy to believe there are other lenses so poor, but I would want to see the tests before I'd accept that there are such modern lenses. I honestly think any telephoto made since 1990 will benefit from a TC.

Of the thousands of posts of images, I've yet to see a single post from someone using the HD DA 1.4 TC or the F 1.7x AF adapter, who claim they got better images by taking off the TC and cropping. It's just odd, that some think we are all fools wasting our money on un-necessary gear.

[zapp]

A generic TC will do fine, you will lose an f-stop or more, so focusing will be more difficult. At the same time you increase the focus area which will compensate for the previous problem.
A dedicated TC, developed along with certain lenses in mind, can result in no quality loss at all. Leica ones presented lens modules, Canon/Nikon/Olympus… have lenses with TC build in. Pentax kicked the 200&560 lenses making space for something else.

[xmeda]

A sharp lens coupled with a good TC will still give you a resolution advantage compared with cropping, even taking into account having to using a higher ISO to counter the loss of light.

I have 1.5x SHQ Kenko, 2x Kenko and 1.7x Pentax AF TC

Results depend highly on lens that is attached. In general 1.5x teleconverter works very well with most lenses. It looses only a bit of light and with lenses like 100/2.8, 70-200/2.8 or 100-300/4 it provides results that are significantly better than crops. Even on 24Mpix K3. If lens has hi-res central part of image, it can even improve overall image. An example - DA18-135 is known to have weaker borders. And if you attach 1.5x TC on it, it magnifies central part that is sharp and crops borders. Results are very good.
But surprisingly even lens like Sigma 50-500 benefits from this TC, it slows down AF a bit, but AF accuracy is better.


2x TC is weaker and I'm using it mostly with tripod. It can AF with most fast lenses, that is no problem. On K3 even Sigma 18-250/3.5-6.3 OS works with this TC and even stabiliser in that lens behaves very well, but it needs light because it is 500mm with F12 equivallent aperture when open and towards F16 for better results, and it also needs at least 1/320s or 1/500s to be sure.


1.7x AF TC from Pentax is somewhere in the middle. But concerning image quality, for some old lenses this adaptor can in fact improve image output significantly, because old lenses tend to have weak multicoating or no multicoating applied at last elements. It was not that important for film. But shiny sensors of digital cameras reflect a lot of light back. And exactly in this case, this adaptor works as additional SMC coated back module for those lenses, which results in improved contrast. And contrast + resolution gives you "sharpness".

[gazonk]

But concerning image quality, for some old lenses this adaptor can in fact improve image output significantly, because old lenses tend to have weak multicoating or no multicoating applied at last elements. It was not that important for film. But shiny sensors of digital cameras reflect a lot of light back.*

*
Interesting point! But also check old lenses for dirty back elements! I thought my old M-135/3.5 was completely useless on digital until I cleaned the back element. But still, after cleaning, I wasn't too happy with the results on my K10d. For some reason (less shiny sensor?!), the K-5 gave better results than the K10d. And on the K-1ii even more so.

[normhead]

*
Interesting point! But also check old lenses for dirty back elements! I thought my old M-135/3.5 was completely useless on digital until I cleaned the back element. But still, after cleaning, I wasn't too happy with the results on my K10d. For some reason (less shiny sensor?!), the K-5 gave better results than the K10d. And on the K-1ii even more so.

The K-5 gave consistently better results than any Pentax before it, for every lens and lens combination. At one time it was 6th in the world on the DxO charts, and is still top 100 today.

[thibs]

*
Interesting point! But also check old lenses for dirty back elements! I thought my old M-135/3.5 was completely useless on digital until I cleaned the back element. But still, after cleaning, I wasn't too happy with the results on my K10d. For some reason (less shiny sensor?!), the K-5 gave better results than the K10d. And on the K-1ii even more so.

The CCD -> CMOS may explain part of this.