I have dedicated an entire bookshelf page to my very favorite lighting (and other photo) books for your consideration. All are well-considered and are, I believe, the very best examples in their genre.
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But beyond that I would suggest you consider the occasional workshop. Nothing beats a hands-on, small class with a solid pro who knows things you would like to know. It is a super growth experience, and something you really owe yourself if you are passionate about learning to be a better photographer.
At this point severe time constraints limit my ability to teach. But in the past I have taught many workshops and worked with many organizations. Having worked as an instructor for Gulf Photo Plus (held late winter in Dubai) and Santa Fe Workshops (held year-round in New Mexico and elsewhere). I can strongly vouch for both of these organizations. I have seen first-hand how students grow in leaps and bounds in the span of a week, all while making great new friends and having the experience of a lifetime.
If you have ever toyed with the idea, you should definitely ask around, do your research and then take the plunge.
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That’s it, For Now
That’s my two cents worth on gear. You may have other choices or priorities, but that is the best I can offer you with 25+ years’ experience behind it.
If you want to chime in on your own, feel free to do so on Twitter via the hashtag #StrobistGear. If is it important that I see it, include an @Strobist in there somewhere and I will.