by Joe Farina » Wed Dec 19, 2018 9:32 am
For your silver emulsion, 1.5mJ sensitivity in the blue is excellent. I'm not sure about my color DCG material, but it probably needs more than 30mJ in the blue. I've often wondered about the necessity of keeping close to 450nm for the blue component of RGB holography. The literature seems to say that it's optimum. Yet, you and Y. Gentet like 473nm DPSS for your silver materials. So I guess the practical difference between 457 and 473 might not be significant, and there may be advantages to 473 from a holographic standpoint. The longer wavelength of 473 would have less scattering compared to 457. I noticed that scattering with the Melles-Griot 457 was quite substantial, and that wavelength seemed to pick up a lot of noise from small particles (dust, etc.). Years ago, I saw a side-by-side comparison of two holograms at Lake Forest of two RGB holograms, both identical, except that one was done with 442, the other with 488. I honestly couldn't tell the difference (although the guy next to me said he could tell a subtle difference). I guess if the object/scene contains blue that is short, less that 473 for example, and that blue component is important, it might be noticeable. But in nature and many natural pigments, I think blue has less real significance compared to red and green. On the other hand, blue should definitely help to "whiten" white. The laser cost of usable 473nm light might be high, possibly comparable to Melles BLD/BLS, I haven't seen many such lasers available over the years, and have never used one. I'm considering a Sapphire at 488nm, mainly to brighten whites. Prices on eBay are looking pretty good lately.
For your silver emulsion, 1.5mJ sensitivity in the blue is excellent. I'm not sure about my color DCG material, but it probably needs more than 30mJ in the blue. I've often wondered about the necessity of keeping close to 450nm for the blue component of RGB holography. The literature seems to say that it's optimum. Yet, you and Y. Gentet like 473nm DPSS for your silver materials. So I guess the practical difference between 457 and 473 might not be significant, and there may be advantages to 473 from a holographic standpoint. The longer wavelength of 473 would have less scattering compared to 457. I noticed that scattering with the Melles-Griot 457 was quite substantial, and that wavelength seemed to pick up a lot of noise from small particles (dust, etc.). Years ago, I saw a side-by-side comparison of two holograms at Lake Forest of two RGB holograms, both identical, except that one was done with 442, the other with 488. I honestly couldn't tell the difference (although the guy next to me said he could tell a subtle difference). I guess if the object/scene contains blue that is short, less that 473 for example, and that blue component is important, it might be noticeable. But in nature and many natural pigments, I think blue has less real significance compared to red and green. On the other hand, blue should definitely help to "whiten" white. The laser cost of usable 473nm light might be high, possibly comparable to Melles BLD/BLS, I haven't seen many such lasers available over the years, and have never used one. I'm considering a Sapphire at 488nm, mainly to brighten whites. Prices on eBay are looking pretty good lately.