I've been learning to use off-camera flash for my eBay photos. The setup is a Canon SX170IS point-and-shoot on manual, with an old garage-sale Vivitar speedlight (one power setting, non-adjustable), triggered from the on-camera flash by a ten-buck optical slave, shot through a cheapo shoot-thru umbrella. The results aren't great by any means, but they're a lot better than what I used to get. Unfortunately, I just can't seem to figure out how to get consistently correct exposures. I understand the theory behind flash exposure - ISO, aperture and flash-to-subject distance. I've read a hundred tutorials on the Strobist and watched a hundred more on YouTube, all of which have been helpful in their own way. I check my histogram and do plenty of "chimping." Yet whenever I bring the photos into my computer and look at them in Lightroom, I see what you see here: images that look decent (for a setup that cost less than $250 total, anyway) but the exposure is inconsistent. Slightly over, slightly under. Once in a while I get lucky, but I can't rely on luck. Sure, I could correct in Lightroom, and I do if I have to, but that's not really the point here. So how do I get consistently correct exposures? Do I need to shoot tethered? Buy a handheld meter? Resign myself to post-processing? I know the answer is out there somewhere, because the internet is full of perfectly-exposed photos, but this is baffling me. Here are a few sample shots. I feel like the first one is pretty close to being right, the second and third are underexposed, and the fourth is overexposed. These were all shot on the same settings (ISO 100, 1/200, f4.5, same flash distance, full flash power since it only has one setting, camera on a tripod) and no post-processing other than resizing and "sharpening for the web." (These photos are the least embarrassing set I could find; I've shot plenty more where despite my best efforts, the exposure is too out of whack for me to even want to look at. ) Thanks for any help!