Photograv is a program designed to convert grayscale images into dithered bitmap (pure black and white) images. It is similar to using the conversion in Photoshop to bitmap mode, or in PhotoPaint to Black & White.

The difference is that Photograv gives far more control over the conversion process than either of those paint programs. Photograv also has simulation built in so you get a preview of what the image might look like when engraved on the selected material. That preview is somewhat useful but not the most important part of Photograv.

I find that the purely automated side of Photograv is lacking in quality compared to the interactive side of Photograv. I can get just as good a conversion to a dithered image from Photoshop by using sharpening and then converting the mode to bitmap. But using the interactive side of Photograv gives much finer control over that conversion and than you can get with Photoshop or PhotoPaint.

The dithering conversion in Photograv (or Photoshop & Photopaint) is far superior to doing a halftone conversion in one of the paint programs. Dithering allows a much higher quality image to be engraved than halftone can ever hope to produce.

If you have Photoshop, then try doing some sharpening and then change the mode of the image to Bitmap. Invert it if needed (dark materials that engrave light need it). Then engrave it. You can also do that in PhotoPaint from CorelDraw.

If you want a bit more control, and expect to be making decent money engraving photographs, then I feel Photograv is a reasonable expense. If you are doing it for the fun of it, or are happy with the results from dithering in Photoshop or PhotoPaint, then you don't need Photograv.