AF360 flash guide number confusion

[sfcole]

<p>In marketing specs given for this flash (including the website), the guide number is given as 99. but when consulting the manual, the giude number for iso 100 at 50mm is only 30, and even at 85mm, it's only 36. In fact, nowhere in the manual does it give a guide number as high as advertised.<br>

I only discovered the real power by testing it with a flash meter.<br>

What's going on here? Are we supposed to believe any of the manufacturer specs for flash? How did they possibly come up with 99?</p>

[danny_wong2]

<p>Are you comparing the same guide numbers? GN are given either in feet or meter. Using the standard rule of thumb coversion factor of 3.3 GN30 in meters equals GN99 in feet.</p>

[noah_maier]

<p>Ditto</p>

[sfcole]

<p>Thanks--in looking back at the PDF manual I have, I didn't realize that the default GN was given in meters. Usually I see it in feet, with meters in (..). This manual may have been intended for a different market. I'll have to retest with my flash meter (just did a cursory pop) and see if I get anywhere near the rated GN</p>

 

[mountainvisions]

<p>Feet and meters are often used, you need to make sure you are looking at the right numbers.</p>

<p>The flash isn't real powerful compared to other flashes, but considering it's a bit smaller than other flashes on the market (not much but enough to notice), it is a very nice little flash. I also think it's a little sturdier because of the lack of swivel (even though I wish it had swivel). Great travel flash with enough pop to keep me happy.</p>

<p>Anyway, I'd recheck you metering, it should be 99 or 30, or close enough!</p>

[mc2imaging]

<p>Here's a trick with Pentax's flash model numbers: They are all based on a formula that defines specific features. In the case of your flash, the AF-360 comes from the guide number of 36 (iso 100, in meters - remember, these are engineered in Japan). The AF-540 has a guide number of 54, the AF-280 is 28, etc...<br>

The letters behind the guide number define which options the flash has as well.</p>

[mc2imaging]

<p>http://kmp.bdimitrov.de/technology/flash_names.html</p>

 

[andrewg_ny]

<p>The GN in Pentax's flash names can be a little misleading or confusing though depending on the use of the zoom head if available. For example, the AF-280T (which lacks a zoom head) is probably a little more powerful than the AF-360FGZ if used at 28 or 35mm.</p>