[Klaus]

It matters because the measurement was at close focus, so the effect might seem worse there than in "reality"?

 

See the sample images. The borders are softer than the MTFs suggest.

 

I think you should get over the idea that the measurements are close focus.

The object magnification is FAR beyond anything that you would consider to be a close focus scenario. Close focus ends a 1:10. At some stage I calculated this - was it 1:50 ? Something like this.

The object magnification is the same across all tested lenses.

 

In any case it just doesn't matter here - the field curvature is visible at infinity.

If I didn't spot this in the sample images I wouldn't have reported it (plus/minus human error that can always occur even during measurements). The MTFs are the beginning of wisdom but not the end of it.

[davidmanze]

I would assume there is touch screen AF in LV, it would probably be sufficient to tap focus at 1/3rd in from the edge of the screen to achieve hyperfocus @7mm AF without all the guess work scenarios for distant scenes.
For my Sigma @ 10mm as the AF at inf. was totally variable I just put a point of paint on the barrel when I had established inf. (non window Pentax version) and focused manually.

[Boby]

The test chart is at around 51x the focal length distance. For 7mm that means around 7 x 51 = 35,7mm distance.

 

 

Rather 36 cm, but thanx.

[Klaus]

Rather 36 cm, but thanx.

 

Actually this is incorrect - it's about 50cm.

 

Object size = 900mm

Image size = 13mm

Object distance = 500mm

-> focal length 7mm for MFT

 

Reference:

http://www.giangrandi.ch/optics/focalcal...calc.shtml

 

0.5m is also the hyperfocal distance at 7mm @ f/5.6, BTW.

 

The hyperfocal distance at 7mm @ f/2.8 is 1.1m.

 

Hyperfocal distance = depth-of-field of half that distance to infinity - assuming a flat focus field that is.

 

Reference:

http://www.cambridgeincolour.com/tutoria...stance.htm

 

And the hyperfocal has very little to do with macro photography. It is a guidance for landscape photography.

[Brightcolours]

Actually this is incorrect - it's about 50cm.

 

Object size = 900mm

Image size = 13mm

Object distance = 500mm

-> focal length 7mm for MFT

 

Reference:

http://www.giangrandi.ch/optics/focalcal...calc.shtml

 

0.5m is also the hyperfocal distance at 7mm @ f/5.6, BTW.

 

The hyperfocal distance at 7mm @ f/2.8 is 1.1m.

 

Hyperfocal distance = depth-of-field of half that distance to infinity - assuming a flat focus field that is.

 

Reference:

http://www.cambridgeincolour.com/tutoria...stance.htm

 

And the hyperfocal has very little to do with macro photography. It is a guidance for landscape photography.

You once wrote that the testing distance is 51x the focal length (that that is not the case apparently, is not on me). Besides that I forgot to take the crop factor into account, which was silly. 

 

Hyperfocal distance should be a thing of the past. Unless one dislikes getting the best results. It is a theory from when print size and resolution usually were limited.

[Klaus]

You once wrote that the testing distance is 51x the focal length (that that is not the case apparently, is not on me). Besides that I forgot to take the crop factor into account, which was silly. 

 

Hyperfocal distance should be a thing of the past. Unless one dislikes getting the best results. It is a theory from when print size and resolution usually were limited.

 

You still wouldn't go for infinity focus for best results either.

[Brightcolours]

Not taking any field curvature into account, indeed focussing at the horizon/infinity/main subject gives the best results.

 

http://www.trenholm.org/hmmerk/DOFR.html

[Klaus]

Not taking any field curvature into account, indeed focussing at the horizon/infinity/main subject gives the best results.

 

http://www.trenholm.org/hmmerk/DOFR.html

 

He's talking about maximizing the depth-of-field which is a different discussion compared to critically sharp foreground corners.

 

In an ultra-wide image I find sharp foreground corners to be paramount - thus where you see object details - whereas I can live with a somewhat less sharp infinity region which is blurred by the atmosphere anyway - thus where the details are reduced anyway.

 

Your mileage may vary.

[Guest]

Any comments on the purple fringing i mentioned in post #4 ?

[Boby]

afaik there is a certain mismatch between Olympus and Panasonic regardings the transmisssion/detection of very short wavelengths (UV or near UV). Anecdotally, the PF appears therefore mainly when using a Panasonic lens on Olympus camera (or/and vice versa - I am not  quite sure here).