I recently switched from shooting 4x5 and 8x10 to a Leaf Aptus 65 on an Arca Swiss 6x9 and have been struggling with the greater demands of focusing for the digital back. I am replacing the Arca GG and fresnel with a Bill Maxwell GG and fresnel, which I currently use on my 4x5, and purchased the Silvestri 6x and Schneider 10x to test both. Below are my observations about the loupes:
I started by removing the lens and adjusting the diopter on each loupe so the ground glass grain was sharp, then tried using the loupes on a scene lite by direct light and indirect light using a 45mm, 105mm, and a 125mm macro lens.
1. Both loupes are well made, but I like the way the string attaches to the Silvestri--a quibble I know until you're out in the field and the Schneider falls to the ground.
2.The Schneider has a wider top element (about 1-1/8" dia.) and reqires you to keep your eye locked into postion more to get the clearest image. The Silvestri has a smaller top element (about 5/8" dia.) and consequently your eye naturally comes to the best viewing position just to see through the loupe.
3. The base of the Schneider is about 2" dia. and the Silvestri about 1-1/4" dia., consequently the Silvestri is much easier to focus at the edge of the frame simply because I can place the optic center of the Silvestri over the frame edge for direct through viewing. Because of the size of the Schneider base, I can't place its optic center over the edge of the frame (it hits the Arca back metal frame), so I must look diagonally through the loupe to focus on objects near the edge of the frame. This makes using the Schneider to focus near the edge or corners of the frame more difficult. With the lenght of lens I use, I found no advantage to using the Silvestri base that allows you to tilt the loupe. (It may be an advantage with wider lens?) The base just made it difficult to focus near the edge of the frame.
4. I have read that higher magnification loupes don't have an advantage for focusing because they just show more GG grain. I would now disagree. The Silvestri 6x and Schneider 10x do show more GG grain, but they offer a much higher degree of confidence focusing because objects snap into and out of focus more. (Curiously, the large GG grain of the Arca GG didn't cause me anymore problems focusing than the finer grain of the Maxwell GG.) When focused in the center of the frame, I thought the Schneider 10x offer a higher degree of snap and confidence focusing than the Silvestri 6x due to the higher magnification. With both loupes you do see the fresnel screen more but I didn't find that to be a problem. (On the Maxwell screen the fresnel appeared as a series of fine black lines that were easy to ignore.)
5. I noticed no difference in the image quality of each loupe either with direct light or flat, indirect light.
6. With the longer 105mm aned 125mm lens the higher magnifacation of the Schneider 10x was less of an advantage.
My choice is the Silvestri 6x because of its narrower barrel and advantages in focusing at the edge of the frame. For those who don't tilt or swing the lens for focus as much and tend to focus on objects near the center of the frame, the Schnedier 10x may have an advantage.
Hope this helps anyone considering the purchase of these two loupes.
Drew Harty
www.drewharty.com