Here are some side-by-side testing results for the Nikon V1
using the Nikkor 10-30mm f/3.8-5.6 and Nikkor 18.5mm f/1.8. This was performed using the Nikon V1 camera, Kowa 883 scope, and 25x LER eyepiece.
I printed out an ISO 12233 Resolution Chart, and set up the
scope approximately 8 meters away.
The camera settings were set as follows for both lenses: ISO
100, Auto Focus, Aperture Priority Mode,
EV -.7 (this is where I usually have it – perhaps 0 would have been
better, but at least it was the same for both lenses). All images were taken using a 2 second timer.
First I used the 18.5mm lens. With the lens wide open, the exposure time
was 1/800 sec.
I switched to the 10-30mm lens, and tried to set it to
exactly 18.5mm (looking at the EXIF data), but was only able to manage 18.2mm
or 18.9mm – perhaps the lens zoom can only be set with a certain
resolution. In any case, I saw the same
results for either 18.2 or 18.9mm, which resulted in an aperture of f/4.5. For the same image the exposure time was 1/320
sec, or about 2.5 times slower than the 18.5mm lens.
I then zoomed to 30mm, where I sometimes shoot, resulting in
an aperture of f/5.6 and exposure time of 1/200 sec.
After cropping in Photoshop Elements, the image histograms
were fairly similar, with the 18.5mm image having a mean count of 85.7 with the
10-30mm image showing a mean count of 90.6 – the 10-30mm image is a bit
brighter.
The images below are at 100% crop, 2400 x 1800 pixels.
18.5mm lens f/1.7 ISO 100 EV -.7 1/800 sec
10=30mm lens f/4.5 ISO 100 EV -.7 1/320 sec
Glenn-
ReplyDeleteWell thought out comparative study, and nice presentation of the results. Since the "subject" is black, in a sense "back-lit", an exposure of EV 0.0 or even EV =+0.3 would likely have yielded better looking photos, but the point about the f1.8 yielding faster shutter speeds is amply proven, as expected for a faster lens. Would love to see a similar comparative study of the 10-30 zoom vs. the 11-27.5 zoom, not as to speed but as to resolution on the chart.
Thanks Len. I did not realize until after the fact that I had not adjusted the EV from it's usual position to 0, but agree that should not affect the primary goal to compare the speed of the lenses and not the accuracy of the exposures.
ReplyDeleteGlenn