On the Cresta one dismantles the shutter and lens assembly and is left with a conical plastic lens holder. In the front there is a metal washer holding the lens in. The advice is to push hard on the back of the lens with a padded chopstick or something to pop off the washer and remove the lens. But I had a hard time pushing the washer out and came to doubt the lens could be removed from the front. This NOT recommended, but I resorted to partially drilling the washer, weakening it so that it would flex and come out. But I was able to conclude that the washer does come off and lens can be removed from the front. If someone did a better job pushing lens out it might be fine, but was for me a little harder than Hawkeye. I got the Cresta II, but am now wondering if I should have gotten a Cresta I because reportedly the first has an f/13 aperture and the later one a f/11 aperture. But it sure is nice that the Cresta natively takes 120 film. Not only does it have a build in yellow filter and closeup lens, the lens housing will also accept Kodak series push-on filter holders just like the Hawkeye. Then you could either the use actual series filter inserts or use some step-rings to set it up to use conventional screw on filters. https://www.flickr.com/groups/flippedlens/discuss/72157666387244478/