Resolution measurements - TZ30 (ZS20) - Many images

Started Apr 3, 2013 | Discussions thread
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J C Brown
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Resolution measurements - TZ30 (ZS20) - Many images
Apr 3, 2013

Resolution vs. aperture plot for 100 ISO images recorded at 34 mm focal length from 1.1 metres

The following images show the arrangements used to assess the resolution of my TZ30 at short and long focal lengths using the test chart described in this post:

http://forums.dpreview.com/forums/post/50706153

LCD display for images recorded at 34 mm equivalent focal length

Test arrangement for images recorded at 480 mm equivalent focal length

View of LCD display for images recorded at 480 mm equivalent focal length

After adjusting the scale, image position and level to the desired accuracy and setting the white balance test images were recorded from a distance of 1.1 metres with a focal length of 34 mm, apertures from F/3.7 to F/8 and ISO values from 100 to 1600 and from a distance of 14.2 metres with a focal length of 480 mm and apertures from F/6.4 to F/8 at 100 ISO.

Central crops from all of these images are available here:

http://www.dpreview.com/galleries/6778033705/albums/tz30-zs20-colour-resolution-tests

Resolution at a short focal length

The following image was shot at a 35 mm equivalent focal length of 34 mm.

Image P1000147r

As illustrated in the above crop the resolution for each colour may be calculated by choosing the smallest E of each colour which can be easily recognised as an E, noting the value of its line thickness and dividing the height of the image in pixels by that value.

Thus for the TZ30 which has a sensor height of 3240 pixels, if the thickness of the lines in the smallest easily recognisable E is 1.4 pixels then the resolution will be 2314 LPH, (3240/1.4).

Resolution vs. Aperture

The results obtained from the seven shots taken at 100 ISO were entered in the above tables and used to create the following plots of resolution vs. aperture for the black Es and for black and the six colours.

As can be seen from these plots, for a focal length of 34 mm the maximum resolution for black and most of the six colours is about 2300 LPH from the maximum aperture of F/3.7 to an aperture of F/5 beyond which it declines steadily to about 1800 LPH at F/8 due to diffraction.

Resolution vs. ISO Value

To investigate the variation in resolution with ISO value the line thickness of the smallest recognisable E of each colour in the F/3.7 image recorded at each of the five ISO values was used as described above to prepare the above tables which were used to create the following plot which shows the variation of resolution with ISO for each colour.

As can be seen from the above plot, the variation of resolution with ISO value for the red, blue, black and magenta Es is very similar with the value dropping steeply from 2300 LPH to 2000 LPH then reducing gradually to about 1900 LPH. For the green Es the result is only slightly poorer but for the cyan and especially the yellow Es the result is very much poorer.

As may be seen from the above 1600 ISO image and from images P1000147, P1000154, P1000161, P1000168 & P1000175 in my TZ30(ZS20) Colour Resolution Tests Album, in addition to the reduction in resolution the increase in ISO value also results in increased spreading of the colour from the letters into the white area between them.

Resolution at maximum focal length

The following image was shot at a 35 mm equivalent focal length of 480 mm at 100 ISO

Central crop from image P1000286M showing the smallest easily recognisable Es

As illustrated in the above crop the resolution for each colour was assessed as described above and the results entered in the following tables. These show that the resolution at the maximum aperture of F/6.4 is about 2000 LPH and declines steadily to about 1800 LPH at F/8.

I hope that the information and test results provided in this post will be of some value to owners of TZ30 (ZS20) and similar cameras.

Jimmy

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J C Brown

Nikon Coolpix P100 Panasonic Lumix DMC-ZS20 (Lumix DMC-TZ30)
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