There are a number of very similar "generic" flashes made in China and sold in the US under a number of different brands, including Sakar, Digital Concepts, Vivitar (all three brands of the same company); also Bell and Howell, Bower, Practika, and Cactus. If you find a flash not listed in this guide, odds are good it's actually one of these.
The current P-TTL-compatible models are:
- DSL28 Series — a small, entry level flash with a slightly-odd tilting reflector, for bounce but no swivel. DSL283AF, DSL286AF, and DSL288AF are alternative front designs, and it's also available as the Vivitar DF-183 and with slight variation as the Metz 24 AF-1.
- DSL88 Series — a very basic flash with a manual zoom reflector, with power equivalent to the Pentax AF360FGZ for half the price. Primarily famous as the Metz 36 AF-5 (with some differences from the Tumax-branded model). This model tilts for bounce but does not swivel side to side; the very-similar DSL98 Series, sold as the Vivitar DF-283, adds that (and a bit more power).
- DPT3 Series — this model (and variations) has been around the longest and is probably the most common. DPT383AFZ, DPT386AFZ, and DPT388AFZ are variations — or Vivitar DF-383 and Cactus AF45. The feature list is pretty good, with bounce and swivel, rear curtain sync, and some level of manual control.
- DPT5 Series — a very interesting new entrant, because it adds wireless P-TTL and a USB port for potential firmware updates for compatibility. Variants are the DPT586AFZ and DPT588AFZ, and it's sold as Cactus AF50 and Vivitar DF-483. (They'd already used up 5xx for a ring flash. Also, Vivitar currently only sells the Canon and Nikon variants)
It appears that the maker of all of these units, regardless of label, is Icorp Enterprises of Hong Kong. The familiar appearance and specifications can be found on the page of products carrying Icorp's own "Tumax" brand, and the corporate web page says:
In addition to producing our own merchandise, we also offer customized design service and the manufacture of private label products to suit the needs of our clients. OEM and ODM customers are welcome.
This is confusing, but I've attempted to sort out the models in a table of OEM models.
Recently, Hong Kong company Harvest One has begun selling these flashes under their Cactus brand through their Gadget Infinity store. In general, I try to keep this guide neutral, but the plain fact is that the Cactus and Metz customer service people are, by a huge margin, the most helpful and responsive of any reseller of these flashes, and since these flashes do sometimes have quality issues, that's very valuable. (Be aware, though, that if you get a bad unit, the Gadget Infinity policy is for you to pay for return shipping to Hong Kong, a risk which obviously decreases the value proposition.)
Cactus is also straightforward with what they are doing; other companies, like Sakar and Bluestar, are effectively brand-management shell companies which bought out classic names like Vivitar and Bell and Howell as marketing gimmicks. Metz was more coy but eventually admitted the connection. However, they strongly emphasize that they develop a custom firmware ("equipped with a special electronic technology which has been developed by Metz in Germany"), and I generally trust Metz as a company.
Note: There's at are reports of incompatibility with the Pentax K-30. Following previous patterns, newer models which work with newer cameras will probably eventually silently made it to market — with no announcement or easy way to distinguish between compatible and non-working models. Models made a year or so earlier will be incompatible with the K-5 and K-r, and so on back. Make sure you double check before purchase, and buy from somewhere with a good returns policy, in case you happen to get an older unit.
Very old models of the DPT3-series flash don't even have P-TTL support, instead using the older Pentax TTL protocol. I am not aware of a good way to tell which it will be without testing.