DA lenses on K-1 II

After picking up a K-1 II at a good price, I finally got round to checking the usable area for my DA lenses on full frame sensor. The list I've seen was based on using the whole area, but I wanted to know how much benefit I might get from the FF view and cropping. Ideally I'd just buy FF lenses, but that's a rather expensive option.

I've created a list showing usable pixel width & height for Sigma EX 10-20mm F/4-5.6, SMC Pentax-DA 16-45mm F/4, SMC Pentax-DA 55-300mm F/4-5.8 and SMC Pentax-DA* 300mm F/4 with HD Pentax-DA 1.4x converter. I also tested the 1.4 converter with the 55-300mm at 300mm.

My method was to take an image (not using hood *) and crop with original aspect ratio, to where the corners are obviously darkening, as that's likely to be acceptable in most cases. From the pixel size of the crop, I calculate the percentage of full frame width & height, and the equivalent focal length of the cropped area. I may not have been entirely consistent with selecting the border, but it's good enough for me. I wasn't judging any other quality here, and I may look in more detail another time.

The image here (300mm+1.4x) for instance would be cropped roughly as shown in magenta, with the black box showing approximate camera crop size:



The list is here as a pdf.

My results suggest all these lenses are able to be used in FF mode, with some level of cropping.

The Sigma really struggled with dark sides, but still works out significantly wider than using cropped mode. Even though 10mm becomes equivalent to 12mm, with camera crop mode it would be 15mm equivalent. There's a little room for using a bit more width by adjusting the aspect ratio.

The Pentax 16-45mm has little benefit using below 20mm, unless using a near panoramic ratio, which would work well for most cases. It is pretty good from 20mm on, and excellent at 28 to 45mm.

The Pentax 55-300mm was a bit of a surprise, very usable at all ranges, even with the 1.4x converter. With the longer range, I'd expect to be cropping, so it's nice to have a bit more room to capture the bird before it flies out of frame.

The 300mm + 1.4x converter was losing a bit more corner than I'd hoped, but it's still able to provide far more than using camera crop mode.

I hope this is of use to those wondering about how useful their DA lens collection might be if they go to full frame. My kit will be fine for me for now.

* I also noticed the Sigma hood is remarkably close to the crop size, a bit over 100 pixel border and near rectangular - this is why I didn't use hoods for the test:



Mike

I don't understand why you have taken this route? There are dozens of inexpensive but top rate FF lenses out there. I certainly can't afford four figures for Self Destructive Modern glass. But I do have a collection of £50 - 100 old timers that will give many of them a really good run. Takumar 200mm f3.5, MacroTakumar 50mm f4, Hoya 25-42mm f3.5, Soligor and Takumar 105mm f2.8 just to name a few.

If you only effectively use the APS-C area of the K1 sensor then you are using less than 16 megapixels so would be better off with a camera having a smaller sensor of 24mp over the same area. I can understand checking out the DA lenses as it makes sense to use what you already have but at some time you will need FA lenses to get the full potential.

The DA* 300mm on its own is FF compatible.

When I tried it photographing deer with the 1.2 converter added I had vignetting and had to crop.

I was using a K-5 II until a faulty SD card damaged the reader. A repair would have been as much as buying another, so I decided to make the move to FF. That means I've got the DA lenses that I will still use until I have time to find something better.

I've got some old glass that I will use as well, but a lot of gaps in coverage. The Adaptall 2 SP lenses are really good, but a little heavy for walking, where the 55-300mm is ideal, and I've nothing FF wider than 28mm.

That's my plan, thinking about a good wide prime, but I want to experiment a bit to decide how wide.

It is, but the 1.4x converter is not. The combination does provide good results, and I could use in crop mode, but there is a lot of extra sensor area that I can use as long as I'm prepared to crop later.

Most of the time with the long lenses, I'm cropping anyway, so it's not too much extra work.

If you are cropping anyway in pp then it makes sense to have the K1 in FF mode all the time. Unless you are shooting action when the faster buffer write times of aps-c mode may be an advantage.

The K3 or KP or the new aps-c model will give you more MP than the K1 in crop mode, but I have cropped the K1 really agressively with excellent results. If you are going to eventually transition to a FF based system with FF lenses your current approach seems the right one.

I looked at those when my K5 broke, and was tempted, but then I saw a K-1 II for £1100 with 421 activations, and couldn't resist.

Example of a severe crop with the K1. The crop does look oversharpened but shows what you can do.

Or this:

I think my cat is eyeing your squirrel for supper

It has that appearance!