</span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (Ed Sukach @ Dec 13 2002, 03:08 PM)</td></tr><tr><td id='QUOTE'>It may help to focus with the enlarging lens aperture wide open. In addition to providing the most illumination possible, it will make the apparent field of focus narrower and the ideal focus will be more easily seen.</td></tr></table><span id='postcolor'>
although your suggestion is based on common experience, you will find that more than a few enlarger lenses will show a significant focus shift when stopped down. Although enlarger lenses are designed for flat field projection, the practical performance is always a compromise within the variety of possible magnification factors and apertures.
Apart from that, the performance of an enlarger lens can be bad wide open making it difficult to find any sharp grain. In my experience, it is always better to use the grain magnifier at working apertures. If the grain is sharp, your picture will be sharp, too, no matter how many degrees you can turn your focus knob around this. However, if you check the edges, too, you will see that there is usually not that much tolerance.
Regarding the original question: if your magnification ratio is too small to get any aid from a grain magnifier, you will not need one. You will need neither the resolution nor the brightness (shorter times) of larger apertures. Simply focus with your eyes and stop down 3-4 f-stops. If your image is intentionally out of focus (i.e. contains no reference details), judge case by the case. Small magnification ratios reduce the visual impact of unsharpness and you may find it useful to add some defocus while printing. In this case, the use of a grain magnifier may even deteriorate your results.