P900: is there a sweet spot (EFL-wise) for detail on distant subjects? A brief test to find out.

Started Oct 9, 2015 | Discussions thread
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nicodimus22
nicodimus22 Senior Member • Posts: 2,946
P900: is there a sweet spot (EFL-wise) for detail on distant subjects? A brief test to find out.
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Hello, folks. As many of us know by now, the resolving power of the P900 decreases as you zoom in on a subject. I'm sure many of you have seen this chart:

^ Courtesy of http://www.ianperegian.com/My_FZ35_38_Webpage/P900_Resolution_vs_FL.html

For a while, I've been shooting most frequently at 2000mm. Recently, I began to think about this chart and wonder...was I getting the most detail possible by getting the most pixels on my subject possible, or was I robbing myself of detail by using the focal length with the weakest resolving power that the P900 offers? Could taking a photo at say, 1600mm and then cropping/resizing it as needed possibly provide a sharper, more detailed image than the 2000mm version?

In an attempt to find out, here is what I did: took a box of oatmeal with small writing on the side, and set it on the roof of my car. Walked about 40 yards away (an average distance for me in the field) and shot 15-20 shots of the box (in aperture mode as wide as it would go) at each of several different focal lengths, measured with the zoom memory feature. I used a monopod for all of the shots to ensure realistic conditions that I normally shoot in. I processed all of the images identically, and then choose the sharpest image for each focal length based on the clarity of the text on the box. Finally, for the purposes of comparison, I cropped out the same (roughly bird-sized) area of the box in each image, and upsized all of the crops via Photoshop to match the 1331 pixel height of the 2000mm crop. Here are the results:

800mm resize

1000mm resize

1200mm resize

1400mm resize

1600mm resize

1800mm resize

2000mm at original size

After viewing them at 100% size, I think the 2000mm version has the best sharpness and detail (although the 1600mm and 1800mm shots aren't too far off.) Below that, yuck. I can't say I'm surprised at these results, but I wanted to be sure.

The conclusion here seems to be that the positive of getting more pixels on your subject outweighs the negative of the P900's lower resolving power at 2000mm. If you can fill the frame with your subject without using all 2000mm, great. That's ideal. If you can't, don't hesitate to use the maximum zoom for the best results in that situation.

 nicodimus22's gear list:nicodimus22's gear list
Nikon D850 Nikon AF Micro-Nikkor 60mm f/2.8D Tokina AT-X Pro 100mm f/2.8 Macro Tamron SP 70-300mm F/4-5.6 Di VC USD Rokinon 14mm F2.8 IF ED MC +7 more
Nikon Coolpix P900
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