Useful Tips from dpreview...

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May 27, 2003
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For those who missed it (buried under discussion threads), here is the cut-n-paste article from one of the member in STF... on Manual Focus and EVF...

for full discussion, look here

The primary difficulty that I've read about difficulty with manual focus on the 7x7 cameras is not really resolution or brightness, it's appropriate use. I've written about this before, for here I'll reiterate my Rules of Thumb (Thumb is a smart finger... ;-):

RoT #1) If you're shooting at wide angle settings and your subject is farther away than 1m or about 3feet, there's very little point to using manual focus. Small sensor cameras have very great DoF inherently, you'll notice that the distance display in the viewfinder runs very quickly from infinity to about 1.5-2m when at wide angle settings, and the amount of actual movement of the camera's lenses inside the lens barrel is similarly very small. I generally reserve manual focus for when shooting between halfway to full zoom positions or when doing close up macro work.

RoT #2) If you want to LOCK a particular focus position for repeated photographs, the best way to do this and take advantage of manual focus is to half-press the shutter release using a spot focus bracket and let the camera's AF lock in the focus position ... it will be more accurate than your eye. Then, while holding the shutter half-pressed, flip the switch to manual focus. The display will report the actual focus distance and will not budge unless you turn the focus ring. Doing this eliminates focus lag on repeated shots, works for telephoto settings too.

RoT #3) Be aware of the aperture setting. Again, the great DoF of this camera works against you when looking for the critical focus point, even with telephoto settings. The F7x7 cameras are NOT single lens reflex cameras ... SLR lenses have what is called and 'auto diaphragm' mechanism which ensures that the lens is always wide open for viewing and focusing, but is stopped down to the taking aperture when the shutter is released and the mirror flips up out of the way. The Sony F7x7 cameras do not utilize a mirror reflex viewing system, and adjusts brightness at the LCD/EVF by other means for convenient framing. What this means is that the lens is stopped down to the taking aperture in most circumstances, which increases DoF and makes it hard to see when the critical focus point is reached.

Exercise: In good lighting, set the zoom to the middle position in the bar and pick a nicely delineated subject about 2m (6 feet) away. Switch to manual focus and Aperture priority. Set the aperture to wide open (about f/2.2) and roll the focus back and forth. Note how you can see the focus change. Now switch to f/5.6 and roll the focus back and forth again... Note that the change in sharpness is much less discernible, your subject moves in and out of focus very gradually.

So, when using manual focus, open up the aperture as much as possible to make seeing the focus point as clear as possible. Re-set the aperture back to the taking aperture desired after locking on your focus point.

RoT #4) The display in the F7x7 cameras refreshes at different rates based upon camera mode and available light. In low light and slow shutter speed conditions, the refresh is slow. That slow refresh rate combined with small camera movements from being hand held make critical focus difficult to discern. There is no way to change this behavior as it is how the viewfinder is kept bright enough to be useful for framing and composition ... The solution is that when you're using manual focus in dim light, put the camera on a tripod or other steady support to eliminate camera shake and maximize focusing clarity.

RoT #5) The metric distance readout in the F7x7 display has one decimal digit precision until you reach sub-1m distances (about .6m at full wide angle, right at 1m for full telephoto). The actual focus control is near continuous (it is in discrete steps as it is driven by a discrete stepper servo, but the number of steps is high; i cannot find a listing but it seems to be at least 256). The distance readout also scales to focal length. This means that you have precision in the readout at wide angle focal lengths and higher ambiguity at telephoto settings if you set the distance by scale.

In general, the best way to use manual focus for subjects at normal distances is to use the AF pre-focus trick mentioned in RoT #2 ... It will pick a distance that is precise to the full resolution of the focus servo and read out the nearest distance value in the viewfinder when you switch to manual focus. Manual settings by scale at such distances can only be accurate to within 100mm, and 10mm at close up settings, which can make a big difference when at wide open apertures and telephoto settings. These are fine for exposures made when stopped down to between f/5.6 and f/8 at normal distances, but be careful when shooting wide open.

In close up work, the best methodology is to mount the camera on a solid support, set up the subject and camera distance for desired perspective, and slowly rack in the focus at maximum aperture by watching the sharpness and ignoring the distance display. Be sure to set the focus at wide-open aperture and then stop down to maximize DoF and subject sharpness.

In macro work (either close to the 2cm wide-angle limit built into the camera or with close-up lenses and the lens set at telephoto settings), do the same thing but there comes a point where the most accurate way to focus is to move the entire camera and subject relative to one another rather than turn the ring. You have more precise control that way.

I hope these RoTs help... Of course, be sure you have adjusted the eyepiece diopter to give you the best, sharpest view of the focusing field.

I know the F828's higher resolution EVF will be a major advance in this area, but the same principles will certainly apply.


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