I'm very much interested in the care of my animals and love to read books on them.

I'm aware that D3 is regulated by the body when exposed to lights, but what I mean with too much UVB might be bad, as it is for us.

If the frogs did not fare well with this then experts/breeders would recommend UVB lighting. These guys literally spend so much time with their frogs, studying them and trying new things. They breed them for a living and so I trust them the most. They would know if something was missing. I believe you breed too don't you? I'd trust what you do with your animals, the species you kept and would take advice. But I fully trust Philippe de Vosjoli's guide to horned frog care and his methods. Working closely with one species and lots of them is the best way to learn how to care for them. I do prefer practical advice rather than theory and UVB lighting with amphibians needs more research IMO and proven results per species, in detailed information on how they were housed, fed and what lighting and for how long they received it. But I'm re-doing my tanks over the next few months and I am putting better lighting on some where I believe will benefit and for displaying the frogs. I'll still use my supplements contain D3, though.

Those were not excuses, but actually concerns. In order to fully rely upon UVB as a the main source of D3 and leave behind the old supplementation regimes, the correct wild index as you know has to be provided. But there's guesswork unless you have the UVB meter and it's pricey. For the light and shade method, for me the tank size does come into consideration. Unlimited space in the wild allows the animal to select many light and heat gradients to it's preference. In small (but not necessarily tiny) tanks often recommended, the animals will not have much choices and could be stressed. This will have to be updated and hobbyists will need to buy larger tanks and create different types of set ups. Breeders aswell, it will be very different and pricier than the current practices. We have a serious interest in frogs, but for someone who simply wants a pet, it's a lot different. They might just want the basics and the animal, not to spend a fortune. Just my thoughts. I do like to have debates on these things,it's a great way to learn and share advice. There's so much to be learn.

I will check it out, thanks!