Stephen Ingraham (who?)
the unofficial site for birders and digiscopers using Zeiss equipment.
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Setting the Diopter on the DC4
If you don't get this setting right, every image you capture will be fuzzy and unsatisfying. Spend the time to make this adjustment before using the DC4 for the first time and your results will repay your effort. Even after the first adjustment, you may want to try it again on occasion, in case the focus of your own eyes drifts (as it does if you have a cold or allergies) and as you become more sensitive to focus issues. This is especially true if this is your first experience with a spotting scope as well as with the DC4. There is an art to focusing a scope accurately that is learned over time.
To get started with the DC4, point the scope and DC4 at a uniform background with little detail (snowy ground, the sky, a blank wall, etc.). It is not necessary for the scope to be in focus. Slowly turn the diopter control until the two concentric circles are as sharp as you can get them, and clearly separated. This will take some doing. Our eyes tend to be very forgiving and adaptable. You will find that you are trying to make the circles sharp with your eyes, not with the diopter control alone. Because of this you will need to rock the focus through the sharpest point repeatedly, until you are convinced it can be no shaper. Correct focus is very subtle thing, and the diopter control is necessarily a very fine focus control. Be patient. Work at it. Turn the diopter past the point of sharpest focus in one direction; then reverse and come back; again, past the point; reverse; back; past; and come back to the point. Note the reading on the diopter scale. Stand up and look at something in the distance to rest your eyes. Try it again. Do you get to the same reading on the scale? Repeat as necessary until you consistently come to the same point on the scale for sharpest focus. Now turn on the DC4 (if you haven't already), and without touching the diopter control, focus the scope on some object in the middle distance which has good vertical detail as you would normally through the eyepiece (building edges, thin branches, letters on a sign, etc.). Again, rock focus back and forth though the point of sharpest focus until you are satisfied it can be no sharper. This is no easier than focusing the diopter and will take as much effort (though, since you are actually looking at something, it will be more fun). During scope focus try to ignore the inscribed circles completely. Just concentrate on the image.
Once you are satisfied with the focus through the eyepiece, stand back and check the focus on the LCD. The image should be nice and clear and sharp. Use the zoom control on the remote to enlarge the image on the LDC to 7x (going beyond 7x produces an image (in real time display) that is too jagged to be any help). Due to the nature of the LCD you won't be able to tell, chances are, if the strong verticals in the image are indeed sharp. Again, rock the focus control back and forth. Moving the focus either direction should make the image worse. If so, then your diopter control is set correctly and you are good to go! If the point of sharpest focus on the LCD does not match the point of sharpest focus through the eyepiece then you have two options. 1) return to the top of this document and start over, exercising even more patience and care this time, or 2) focus the image on the LCD as sharply at 3 or 7x as you can, then focus the scope using the diopter control (not the main focus knobs). In either case make a note of the correct setting on the diopter scale once you have found it. For most people, this procedure, which can take 20-30 minutes the first time you try it, will work to establish and exact match between the scope focus, according to your eyes, and the sensor focus and you images will sharp and crisp whenever you have the scope clearly focused. If, however, you are still not getting sharp images when you are confident the scope is correctly focused, it may be necessary to resort to the trial and error method. Begin by following the above procedure to establish what you believe is the correct diopter match. Note the diopter setting. Focus carefully on a high contrast object with strong verticals. Take an image. Move the diopter control a fraction of a turn either way, record the new setting, refocus, and take another image. Move the diopter again in the same direction, record, refocus, capture, etc. for several images. Then put the diopter back to the original setting, refocus, and take a series of images on the other side of that setting, turning the diopter the other way. Keep careful record of where the diopter was set for each image you capture. Download your image set to you computer, and open the images in a good image editing program. Pick the one with the best focus. Set your diopter control on the DC4 to the corresponding setting. That should be the perfect setting for your eyes. Should be...because getting the diopter right is only half the battle. Even if it is right you still have to focus the scope correctly, and, as I said above, that is an art that requires practice. Focus for image capture must be much more precise than focus for observation. You eye forgives and adapts. The sensor in the camera does neither. As with so much else in life, the only cure for this predicament is practice, practice, practice. And, this whole explanation makes it sound harder than it is. Most people will successfully set the diopter in 20 minutes, and will bring back a high percentage of properly focused image right from the start. For further instructions, and other reasons your images might not be sharp...see Getting Satisfying Images with the DC4. |
The single most critical setting on the DC4 is the diopter. Because every person's eyes are different, you must match the focus of your eyes through the scope to the focus of the scope on the camera sensor. If you look through the eyepiece you will see that we have provided a focus aid, two concentric circles inscribed on the reticle of the eyepiece, to help you. 
