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Full Version: next PZ lens test report: Olympus M.Zuiko 7-14mm f/2.8 Pro
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Quote: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.


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

Quote: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.
Quote: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.

Quote: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.

Quote: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.
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

Quote: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).

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