** Important ** For the unscaled images of the solar disk, click on the images to display them in full size.
** IMPORTANT!! ** All images in this post were taken through a professional solar filter. DO NOT image the sun without proper filtration!!! You could suffer permanent vision damage. Your camera will also suffer burns.
Image scale is an interesting topic. When photographing a solar eclipse, we want to capture the details most interesting to the observer. Some will want to get wide field images of the corona. Others will want to get the inner corona and perhaps prominences. Others will want to capture images that provide a view of the eclipsed Sun with the surrounding star field. Yes, stars are visible during eclipses, and the 21st August 2017 eclipse gives us a remarkable show with the star, Regulus, within the field of view!
This article gives three examples of image scale to consider. All images were taken with the same camera body, a Nikon D810a in full frame, FX, mode using 36.3 megapixels in raw mode. The full frame images were reduced to better fit the page here, so have been reduced to 20% of the original. These shots allow you to see the scale of the solar disk with regards to the full scale frame out to the edges. Following each of those images is a cropped section of the original image, unscaled, so left at 100% scale, of the Sun’s disk. Be sure to click on them to see their full size. Three lenses were used: 200mm, 300mm, and 500mm telephotos, all FX. All images were shot through a Baader Solar Film filter covering the lens’ objective.
The 200mm lens is a good choice for wide field shots of the Sun and surrounding field of view (thinking of seeing the star field), and the outer edges of the faint corona. The full image is 7360 x 4912 pixels. The Sun is just over 390 pixels in diameter at this scale. This means the image is about 19 solar diameters across and 12.6 solar diameters in height.
The 300mm lens is a good choice for the outer and inner corona as well as shots of any prominences, Baily’s Beads, and the diamond ring effect. This is a good all around lens for a lot of other photography as well (birding and the like). This is also a light weight lens, so travels well, attaches to tripods well without shaking, and yet takes good images for eclipses. The full image is 7360 x 4912 pixels. The Sun is about 545 pixels in diameter at this scale. This means the image is about 13.5 solar diameters across and 9 solar diameters in height.
The 500mm gives us a little more magnification, offering the great views of the inner corona, prominences and such. It is heavy, and pushes tripods to their limit unless you get a beefy one. The larger lens profile also catches wind more easily, so might present issues with shaking on a windy day. Wind tends to die down during the totality, though… a good thing. The full image is 7360 x 4912 pixels. The Sun is just about 920 pixels in diameter at this scale. This means the image is about 8 solar diameters across and 5.3 solar diameters in height.