P900 Resolution vs Focal Length

 


The Variation of Resolution of the P900 with Focal Length


The camera review sites generally only test camera models at a single focal length, usually at around 70-100 mm EFL.  Since the Nikon P900 is the first fixed lens zoom camera to become available with a focal length of up to 2000mm EFL, I thought it important to measure the resolution at a range of focal lengths up to the maximum of 2000mm.


The difficulty with testing at very long focal lengths is that a long distance is required between the camera and the chart board.  As far as possible, I used the resolution charts printed at 4cm length for the 400 pixel scale line.  However, for testing beyond 1200mm EFL, because of limited space, it was necessary to use the charts printed at 3cm length for the 400 pixel scale line.  The smaller charts required printing at the limit of the Epson XP-600’s resolution capability, and on close inspection it was seen that the lower rows of triplet lines showed lines which were thicker than, rather than equal to, the spaces between them.


Even though the resolution of the P900 would yield readings higher than the faulty triplet rows, it was necessary to determine whether reliable results could still be obtained for the higher rows with the smaller charts.  I therefore tested, under the same conditions, the 4cm scale line charts versus the 3cm charts at 1200mm EFL, being the longest focal length at which the 4cm chart could be used in the available space.


The results showed that both sized charts gave similar results, although the black triplet lines on the smaller chart images were less distinct and showed a somewhat lower contrast.  As far as possible I took that into account for the tests carried out with the smaller charts at 1500mm and 2000 mm EFL.  For all these tests I used the “Standard” picture setting with normal NR, 100 ISO, and the widest available aperture at each focal length.


Test Images


Below are test chart images for various focal lengths. (Click on an image for the full sized view.)



Test image for 85mm EFL, 4cm scale line charts



Test image for 550mm EFL, 4 cm scale line charts



Test image for 1200mm EFL, 3 cm scale line charts



Test image for 2000mm EFL, 3 cm scale line charts



Results


The results of the resolution tests are shown on the graph below. (Click on the image for a larger view.)



Plot of resolution (LPH) versus EFL for the P900


The results show that the resolution of the P900 declines slowly from about 500mm EFL up to the mid range of the zoom and then shows a further gradual decline up to 2000mm.  Considering the very wide zoom range of the P900 lens, the decline in resolution is relatively quite small.



Return to Previous Page


Return to P900 Testing


Return to Home Page