TZ100 versus TZ80 IQ

 



Comparing the Image Quality of the TZ80 with the TZ100 at 4:3 Aspect Ratio


As I have both cameras, I was interested to try to evaluate how, in good light, the TZ100 with its 1” sensor and 25-250mm EFL zoom range, would compare in terms of IQ and reach with the TZ80, with its 1/2.3” sensor and 24-720mm zoom range.  The object was to see what region of the TZ80’s zoom range would be equivalent in IQ to a cropped image from the TZ100.  Obviously “equivalent IQ” can be a very debatable and subjective matter.  In this case I was not considering IQ in terms of printing but rather in terms of my own purposes, which are for on-screen viewing or for producing travel slide-show movies.


As discussed under the features of the TZ100, it has a 3:2 aspect ratio sensor with an image size of 5472 x 3648 pixels.  When set to 4:3 aspect ratio (to match the aspect ratio of the TZ80’s sensor) the TZ100 has an image size of 4864 x 3648 pixels (the left and right sides of the image are cropped but the height remains the same).  The 4:3 aspect ratio image size of the TZ100 is almost exactly the same as the 4896 x 3672 pixel image size of the TZ80 in 4:3 aspect ratio.  Thus a direct 1:1 comparison is possible between 4:3 aspect ratio images from the two models.


While it would be possible to take shots from the same tripod positions using the maximum zoom of 250m for the TZ100 and to compare manual crops of those images with images from higher zoom settings of the TZ80, that is rather a cumbersome procedure.  Instead, I used the TZ100 with iZoom enabled. The way iZoom functions on the TZ100 is to provide digital zoom up to a factor of twice the optical focal length, and which is implemented together with iResolution, which provides a small amount of selective in-camera sharpening.


The 4:3 aspect ratio of the TZ100 has a slightly narrower FOV (field of view) than the 3:2 aspect ratio, so that when 4:3 is selected, with 4864 x 3648 pixel image size, the effective optical zoom range becomes 27-270mm EFL.  However, this change is not shown in the zoom settings on the LCD/EVF, which simply show the 3:2 ratio FL range.  When iZoom is enabled, the iZoom FL range above the optical zoom maximum (shown as 250mm, actually 270mm in 4:3) is shown in pale blue in the zoom bar on the LCD/EVF, and the maximum shown is 500mm (actually 540mm in 4:3).


For the following tests I used tha same setup, chart board and lighting as I used for the resolution measurements shown here, and I used settings of 80 ISO for the TZ80 and 125 ISO for the TZ100 throughout, with aperture settings at the optimum for each camera and FL.  I used JPGs at default settings throughout since it isn’t possible to record RAW files with iZoom enabled.


Comparison using iZoom at 500mm and 18MP


For the first test, I took shots with the tripod set to the distance required for obtaining 400 pixels for the height of the scale line on the centre resolution chart, with the TZ80 at 500mm optical zoom in 4:3 aspect ratio and an image size of 18MP (4896 x 3672 pixels).  Keeping the tripod in the same position, I replaced the TZ80 with the TZ100, and took shots with the TZ100 set to iZoom in 4:3 aspect ratio, as described above.  I set the zoom lever on the TZ100 as close to the framing of the TZ80 as possible, having regard to the step nature of zoom, which in this case gave 512mm EFL.


Results

Below is the TZ80 image taken at 500mm (click on the image for the full sized view):



TZ80 at 500mm EFL and 18MP


Below is the TZ100 iZoom image taken at the same distance and framing (click on the image for the full sized view):



TZ100 iZoom image at the same distance and framing


Below is a comparison of 100% crops taken from the two images, with the TZ80 at the left (click on the image for the full sized view):



Comparison of 100% crops from the above two images


The TZ80 at 500mm gives a centre resolution of 2160 at f/6.1  When viewed at 100%, the comparison shows that the TZ100 iZoom image shows considerably less fine detail than the TZ80 image, although otherwise the IQ is good.


Comparisons using iZoom and 9MP


To increase the iZoom range on the TZ100 to greater than 500mm EFL it is necessary to reduce the image size.  When the image size is set to 9MP (3456 x 2592 pixels) in 4:3 aspect ratio, the camera uses a centre crop of the sensor.  At maximum optical zoom this gives an effective FOV equivalent to 3672/2592 x 250 = 354mm EFL.  Thus the iZoom range is increased up to a maximum of 702mm EFL in 3:2 aspect (758mm EFL for 4:3 aspect).


Following the same procedure as above, but with the TZ100 set to 9MP and iZoom, I took shots with the TZ80 and TZ100 at the same distance and framing for zoom settings of the TZ80 at 400, 465, 500, 600 and 720mm EFL.  Since the TZ100 images were 9MP in size, I downsized the 18MP TZ80 images to the same size of 9MP for comparing them.


Comparison using iZoom at 500mm and 9MP

Below is the TZ80 image taken at 500mm, downsized to 9MP (click on the image for the full sized view):



TZ80 at 500mm EFL downsized to 9MP


Below is the TZ100 iZoom image taken at the same distance and framing (click on the image for the full sized view):



TZ100 iZoom image at the same distance and framing


Below is a comparison of 100% crops taken from the two images, with the downsized TZ80 at the left (click on the image for the full sized view):




Comparison of 100% crops from the above two images



Comparison using iZoom at 400mm and 9MP

Below is the TZ80 image taken at 500mm, downsized to 9MP (click on the image for the full sized view):




TZ80 at 400mm EFL downsized to 9MP


Below is the TZ100 iZoom image taken at the same distance and framing (click on the image for the full sized view):




TZ100 iZoom image at the same distance and framing


Below is a comparison of 100% crops taken from the two images, with the downsized TZ80 at the left (click on the image for the full sized view):




Comparison of 100% crops from the above two images



Comparison using iZoom at 465mm and 9MP

Below is the TZ80 image taken at 465mm, downsized to 9MP (click on the image for the full sized view):




TZ80 at 465mm EFL downsized to 9MP


Below is the TZ100 iZoom image taken at the same distance and framing (click on the image for the full sized view):




TZ100 iZoom image at the same distance and framing


Below is a comparison of 100% crops taken from the two images, with the downsized TZ80 at the left (click on the image for the full sized view):




Comparison of 100% crops from the above two images



Conclusions


As would be expected, images from the TZ100 using increasing amounts of iZoom show reduced resolution of fine detail in comparison with TZ80 images taken in its optical zoom range.  However, as the general IQ of the TZ100 images appears better in comparison with the TZ80 in terms of contrast, colour rendition and dynamic range, it appears possible to obtain TZ100 images using its iZoom range which may be considered acceptable.  Up to what amount of iZoom is acceptable would depend on personal preferences and requirements.


I found that the iZoom results from the TZ100 for 600mm and 720mm were unacceptable, due to an excessive loss of detail in comparison with the TZ80 optical zoom images.


To help determine what focal lengths I commonly have used with my TZ cameras on travels, I ran the free software program called ExposurePlot.  From the results on the thousands of images I’ve taken I found that only a small proportion of the images were taken at focal lengths beyond about 400-500mm EFL.  I mainly use my TZs at or near maximum FL for local shots of wildlife, etc and for telemaco shots.  Therefore it seemed that my TZ110 should be adequate for travel if I use a limited amount of iZoom when required.  From the above comparisons, it seemed that iZoom with the TZ100 at 400mm should be acceptable for limited use, and possibly occasionally even up to about 450mm EFL.





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