I have been using a DIF1 diffuser in my L1200 since I've had it. I also have a DIF2 which I've never used. The DIF1 is only half the thickness of the DIF2 so I have always assumed it gave less diffusion and therefore sharper projection than the DIF2. However, I just held them both upto the light together, and if anything the DIF2 transmits more light and is fractionally less diffuse than the DIF1 which has a milkier perhaps more dense appearance even though it is only half the thickness of the DIF2. I'm just wondering what other peoples experience with these two diffusers is? Just to add for those who are not aware. The 4x5 diffuser which sits directly above the negative on a Femobox 450N. They are exchangeable. One end of the retainer is sprung and you can pull it back to get the diffusion sheet out.