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

In brief (not something I've tried yet, but I'm looking into it).

Start with simple shots, to get an idea of what's possible in terms of sky view - use high ISO and accept the noise to start with. Probably will need to turn off shake reduction. Once you have the basics giving you an idea of what's possible, then try the aststrotracer. From my understanding, that should be the difference between a noisy shot with a few stars and something that will show the sky in more detail than you can normally see.

Use the prime, and get the best view of the sky possible. Nearby lights will cause problems, so learn how to cope with them. Experiment with the widest shots with the zooms as well, but also the longest zoom for some shots of the Moon, and maybe Venus (look West on a clear evening). I suspect the prime lens will be the best, but you need to experiment to see what suits your own style and preferences.

Use a good solid base (tripod or rock with a non-slip mat). If you can get hold of a remote trigger, that will help, but timer delay (to reduce initial shake) will probably be fine for stars,

Practice at home, in various light conditions so you can use the same technique based on what's possible when you arrive.

More important, enjoy experimenting.

Mike

Mine's 7959x600 (it was about three times that, but most software struggles with the width). It displays as a rather narrow strip - probably lucky for me in this case.

Mike

A happy customer - quick & easy purchase and camera has clearly been looked after well.

PM sent re GX10.

Monocular arrived today, well packaged and exactly as pictured. It's a very nice addition to my lens collection!

Thanks
Mike

Hi,

I'm a newbie here, and not that experienced in photography!

Is the monocular converter still available? I think this would be useful to attach to a spare lens for bird watching, possibly to a 400mm or a 200mm.

Also do you know if it would this work with a teleconverter? I can't see any reason for it not to.

Cheers
Mike