I don't own a lot of lenses, but too many for any reasonable person not afflicted with GAS
. I decided to do another round of tests to become a little bit more consistent in my evaluation. I found a test chart referred to on Luminous Landscapes (
New custom DNG profile for Pentax 645z) wherein the reviewer took a picture of a chart with the 645z DFA 55mm @ f2.8. He provided the DNG file in full resolution.
http://213.112.34.223/ekr/Articles/P645D_vs_P645Z/
The chart goes to a maximum of about 12.5 lines per mm and the 55mm lens could resolve that with ease. I printed the test chart at the maximum resolution on my printer which did produce some fuzziness from 10 lines per mm onwards. Using the supplied image I could establish some calibration for the loss of resolution.
Overall I would say of the lenses I tested I did not find any lens that I would say it should not be in my bag at any given time. They are all excellent lenses but there are a few exceptional super performers in the bag. I list below the lenses I tested and what I have found in my own unscientific way.
DFA 25mm - Great lens - resolving 9 - 10 l/mm (lines per mm)
DA 28-45mm - Super performer - resolving 12+ l/mm
FA 45-85mm - Great lens - resolving 11 - 12 l/mm f8 to f11
DFA 55mm - Super performer - resolving 12+ l/mm
FA 80-160 - Super performer - 12+ l/mm f5.6 to f11
FA 120 - Super performer - resolving 12+ l/mm @ f 5.6 to f16
FA* 300mm - Unfortunately something went wrong with my tests shots and I will have to re-do. From previous tests I am inclined to list it as a super performer
FA 400mm - Almost super performer resolving 12 l/mm at f8 with comfortable 9 to 10 l/mm from f5.6 to f16. (Sweet spot at f8).
FA 400mm with TC 1.4 - Good combo with 9 to 10 l/mm at f8 & f11. Outside of the sweet spot it drops off dramatically. The f8 & f11 is the reading on the camera, not the actual aperture.
FA 400mm with TC 1.4 and TC 2.0 - Surprisingly good combo with 9 to 10 l/mm from f5.6 to f11. These are the aperture readings on the camera, not the actual aperture.
A* 600mm - Super performer resolving 12+ l/mm from f8 to f16.
A* 600mm with TC 1.4 - Super performer resolving 12+ l/mm at f5.6 & f8. This is the aperture readings on the camera, not the actual aperture.
FA 150-300mm - This lens is currently with my son, but as I recall and from pictures I took previously, this lens would be in the super performer group as well.
The surprise lens was the FA 400mm lens with excellent resolving capability. The only drawbacks are that it shows a lot of fringing and CA in high contrast settings.
So lenses I can absolutely recommend are the ones in bold above. The others are great lenses and will produce great results, they may just not be the top of the list I could test. One day I may be willing to spend USD500 or more on a pro resolution chart and then I can get even better results, but for that I'll rather buy another lens, or go somewhere to take pictures.
Notes for those interested: 1. My tests are the results of the lens and 645z camera combined.
2. The lighting was not calibrated and I had to set the white balance in the completed images
3. The resolution chart was printed at home at 4:3 aspect ratio and is 400mm high.
4. The image in Photoshop was sized accordingly to avoid distortions, yet at finer resolutions my printer could not adequately distinguish between the lines.
5. Sizes and lines per mm was measured in Photoshop once the size was calibrated.
6. The supplied image taken with the 645z and DFA55mm was much sharper than the equivalent image I took at the same settings of the reproduced chart. This drop in quality was taken into account in the assessment of the lenses.
7. I did not test the drop-off in resolution between center and edge of frame. This was done on purpose, because I was not interested in setting a standard for lenses, I was attempting to set them in order of highest performance, since they are already in my bag. My assumption was and is that all lenses in my bag will be sharper in the center than at the far edges.
8. The chart I used is not an ISO chart, yet is has many similar gradients at similar sizes.
Edit: changed FA 80-160mm and FA* 300mm lenses to bold as originally intended.
Last edited by TDvN57; 08-13-2021 at 12:22 AM.