Fuji S1-Pro Focus Test

By Kenneth R. McVay

Only having the S1-Pro for a couple of months, I was noticing that my images did not seem critically focused as with my other digital slr's. I use manual focus almost exclusivly with the aid of focus assist and after hearing about others having the same problem and the test they were performing, I decided to test this problem myself.

Materials used

• Ruler
• Paper cut out and bent at 90 degree angles
• Nikon 180mm f2.8 lens
• Fuji S1-Pro camera body
• Gitzo tripod
• Graf Studioball ball head with Arca Swiss plates
• 1 gig Microdrive
• Adobe Photoshop version 6
• Clear tape

Methods

Paper strips were cut at different lengths and bent at 90 degree angles. These strips, starting with the shortest, were labeled 1 in, 2 in, ... , 8 in. These strips were then taped down to the ruler at the corresponding measurement marks. The ruler was then placed on a table to be photographed along it's long axis. The S1-Pro camera body was then mounted on the tripod and ballhead via the mounting platesand the Nikon 180mm f2.8 lens was mounted to the S1-Pro. The S1-Pro was then set up just outside the minimum focus distance (MFD) for the 1 in mark. This was done placing the camera inside the MFD and moving the camera back and focusing on the 1 in mark until focus could be achieved.

The ruler aperatus was then photographed by first using autofocus and focusing on the 4 in mark as can be see in the photograph titled Autofocus. Next the ruler aperatus was photographed by using focus assist. This was done by moving the whole ruler out of focus and then slowy bring the 4 in mark into focus. I stopped turning the focusing ring with the dot first appeared in the viewfinder. The resulting image is titled Focus assist at the top of this document. The last photograph made was achieved completely with manual focus and the resulting image is titled Manual focus at the top of this document. All images were taken using iso 800, f2.8, 1/30 sec shutter speed.The camera settings were all original, sharpening was turned off, and white balance was set to auto. This set up was never changed while aquiring any of the three images.

The images were then loaded into Photoshop cropped down and resized to 400 pixels on the long axis. Unsharp mask was applied to all three images with the exact same settings of 120, .7, and 0. Text titles were then added to the top of the images for identification purposes. The images were saved as JPEG using a compression of 9.

Conclusions

It is obvious that the autofocus image is not in critical focus and is the worst of the three as can be seen from the above image titled Autofocus. The image Focus assist image is slightly better but both appear to be focusing in front of the intended focus point. The point is made clear by looking at the Manual focus image. Looking closely at the Autofocus and Focus assist image one can see that the 3 in mark is much better defined then the Manual Focus image. The manual focus image is what one should expect with the depth of field (DOF) better behind the focus plain. And this is the case in this Manual focus image with the 5 in mark being a bit better defined than then 3 in mark.

I believe that Fuji somehow did miss this when building these cameras or they knew about it and let it go. One cannot blame it on the N60 body just because it is not the same quality as an f5. This camera should be able to achieve critical focus as I have tested the N60 film body and it achieves critical focus with autofocus. A camera that cost as much as the S1-Pro should be able to autofocus properly and the question now is what is Fuji going to do about it.