2014年10月1日 星期三

Basic of lens test on Olympus E-PL6 (English Version)


中文版請點擊這裡.

Here is the test procedure for lens in this Blog. Some of the test result will be ranked in "Excellent"  "Good"  "Average"  "Poor"  "Fail"  five degrees.
 
Vignetting:
The vignetting means the losing light around the corner. Shooting at whit paper by different iris at “A” mode, exposure +2EV, ISO 200, focusing infinity. Inspection the dark corner. 

Corner loss 2EV

Corner loss 1.5EV

Corner loss 1EV

Corner loss 0.5EV

Corner loss 0EV


Distortion:
Distortion is a parameter for measuring the optical aberration for straight line. Shooting at the TV pattern on “P” mode, +2EV, ISO auto. It must be recorded in RAW file and transfer to JPG without lens correction. Inspection the edge aberration of the image. We rank this item by Excellent, good, average, poor and fail 5 degrees.

This is the sample pattern
 
Excellent
 
Good
 
Average


Resolution:
The resolution means the ability to render details. Shooting at a resolution sample chart to understanding the contrast detail at center, beside center(1/4 from center), middle(2/4 from center), border(3/4 from center) and corner. Camera setting at different iris , +1.3EV, ISO 200, RAW file. 100% crop at 1800 lines (number 18) and compare the lines be reproduced. We rank this item by Excellent, good, average, poor and fail 5 degrees.

Resolution Sample Chart
  
Excellent

Good
 
Average

Poor

Fail

For new version of the resolution test chart we added the vertical resolution line pattern from 1200 to 4000. The size of this chart is 1.5 meters, for the lens has focal length greater than 50mm. For the lens has focal length shorter than 50mm, we use the 3 meters chart with resolution line pattern from 1500 to 6000. The ranking is based on the clear black/white line’s number on resolution pattern at center of frame, 1/2 of frame and border. Here are the 1.5 meter chart and 3 meters chart(only show the 1/4 of chart).
1.5 meters chart
1/4 of 3 meters chart

Chromatic:
The chromatic means different refractive in different wave length on lens. 100% crop the left up(or down) corner area with black/white edge of resolution sample chart. Inspection the contrast edge with red/cyan fringe. We rank this item by Excellent, good, average, poor and fail 5 degrees. 

Excellent

Good

Average

Poor

Fail


Ghosting and Flare:
Ghosting and flare means non-objective light spot on picture. Shooting at light source with F/5.6 and inspection the light spots on picture. Here is the flare of Olympus M.Zuiko 25mm F1.8 at F/5.6




Sun Star:
Shooting with a light bubble in a distance by F/8, speed 4 sec, ISO 200. The distance is dependent on the focal length (focal length x 300). For example if the focus length is 15mm then the shooting distance is 4.5 meter. Inspection the 100% crop center and the other 8 border areas. We rank this item by Excellent, good, average, poor and fail 5 degrees.

Excellent

Good
Average


Poor

Fail


Coma Aberration:
Shooting with a LED light source in a distance at F/5.6 1/4S ISO200. The distance is focal length x 300(For example if the focus length is 8.5mm then the shutting distance is 2.55 meter). Inspection the light aberration for 100% crop at center and right up corner. We rank this item by Excellent, good, average, poor and fail 5 degrees.


Center(for reference)

Excellent

Good

Average

Poor

Fail


Magnification: 
Shooting with a ruler by close distance. Read out the landscape scale on ruler. The magnification is the 17.3mm/scale. Here is the magnification of Olympus M.Zuiko 25mm F1.8(17.3mm/105mm=0.165).



Details of picture:
Shooting with a doll by half high of the frame. Inspection the details of 100% cropped image. Here is the 100% crop of Olympus M.Zuiko 45mm F1.8 at F/5.6.



Defocus Aberration or Bokeh:
Shooting with a ceramic doll in front of a christmas tree by iris F/minimum, F/2.8, F/5.6 and F/11. The shutting distance to the ceramic doll and Christmas tree are focal length x 37.5 and focal length x 150(for example the distances of a 12mm lens are 45cm to front target and 180cm to background. ). Inspection the bokeh with 50% crop. Here is the bokeh of Olympus M.Zuiko 25mm F1.8 at F/2.8.