Q&A: Aperture and blur, convention lenses, canon flash, and Gary Fong accessories…

More question and answer time! I answered this question before the last one I posted, but didn’t get around to posting this one. 🙂

question. having worked with a number of nice lenses, how big a difference would you say the difference between a 1.2 and a 2.8 aperture makes?

I think it depends on what you are interested in doing. If you are not interested in super smooth background blur or keeping your ISO as low as possible, then f2.8 is a decent fast-enough aperture for a lens. For example, I used a 40mm f2.8 lens most of the time at Otakon 2011. F2.8 isn’t that fast for a prime lens, but it is good enough because I was planning on using an external flash whenever I used the lens. F2.8 with the right settings and composition can produce really nice background blur.

As I’m sure you know, some convention settings are dark with yellow colored light (dealers rooms or hotel settings). In those settings, f2.8 is alright if you are willing to crank up your ISO a bit, but there are negatives with that such as lower dynamic range and higher grain. Newer camera bodies like the 7D do help in that regard though.

On the flip side, generally shooting at wider apertures means you have less sharpness throughout the image, plus if you shoot more that one person you run the risk of getting one of their faces slightly out of focus unless you make your aperture smaller. A plus of large aperture lenses is that they tend to have a larger range of aperture sizes where the lens will produce very sharp results. For example, a 35mm f1.4 lens will start getting really sharp around f2, but a zoom lens that starts at f2.8 is likely not that sharp until f4. There is a measurement called MTF that would be good to research. Every lens has an optimal aperture to produce their sharpest results. Many lenses are around f5.6, but super wide aperture lenses can sometimes have their optimal sharpness at a larger aperture than that. I like the site photozone.de for technical lens reviews.

For me personally, I’m on a quest to produce full-body shots that have really nice background blur. The challenge is that it doesn’t really fit with hallway convention photography. To get full-body + blur means I need a super large aperture plus a lens that will magnify the blur (meaning a lens with a longer focal length). The big challenge there is that I need to be a considerable distance from someone to get their whole body in the photo, so that isn’t a good setup but I keep trying to get there. This goal of mine brought me to the 85mm f1.4 lens. I think it has what I’m after, but I need to make the situations work, which probably means more private shoots or asking more of random people that I ask.

i’m trying to prep for youmacon and i figure i can probably afford to rent one nice lens, and with some testing i figured that a 24mm lens (with crop factor included) needs about 15 ft to get a full person profile in a shot. on the other hand a 16-35 would grant a much shorter distance, only about 8 ft, but the smallest aperture is 2.8. also, if it doesn’t make too big a difference, there is also a 24-70 2.8, but that 24 1.2 just sounds amazing. so i’m just wondering how noticeable a difference it’d make, in your opinion.

Oh, Youmacon… nice.

24mm f1.2? Probably the 24mm f1.4 lens? I don’t think anyone has a f1.2 in 24mm.

To figure out what it can do background blur wise, check out a site like this:
http://www.dofmaster.com/dofjs.html
24mm f1.4 at 15 feet will give you 6.6ft of DoF (sharpness). Beyond that you will start getting blur. Around 7 feet is still pretty big, but manageable to get some nice background blur. 24mm at f2.8 at 15 feet jumps up to 15.5 feet DoF. Basically, if you have people around your subject within 15.5 feet they will be “acceptable sharp” and make your subject stand out less. That 24mm f1.4 sounds amazing, but I like special prime lenses like that. One other aspect of wide angle lenses is that the blur won’t ever look as smooth as a longer focal length lens because there isn’t any magnification going on.

also, while i’m at it (sorry, this is getting rather long) do you know if there’s another way to power a speedlite flash other than AA batteries? i’ve been looking around but i can’t seem to find any other way, but with my flash it seems to devour batteries, and if they don’t die out within hours they overheat to the point that the flash stops working. i’m sure there must be a better way, since i know professional photographers use flashes much more rapidly and longer than i do.

That might be partly due to how you use the flash. As you mentioned in the second message, there are battery packs available for some flash units that will extend the battery life and/or improve the firing speed. If you flash has a tendency to overheat, be mindful of the flash itself because that might be the next thing to fail from heat if the battery back can keep up. I have a simple Sigma flash and use Eneloop NiMH rechargeable AA batteries. Never really had any issues, but I generally take 1-3 shots per person and then it is at least a 10 seconds between the next.

and lastly (this is a stupid question i know, but i figure it’ll make my amazon questing go a bit quicker) the diffuser heads that look kinda like cylinders that a lot of pro shooters put on top of their flashes, what exactly are they called? and do they make that big a difference in comparison to just using the built-in pop on diffuser? sorry, this is all a lot of questions, but i don’t know too many other avid shooters :/ hope you don’t mind, and thanks

Those are Gary Fong Lightspheres. I personally use a small Stofen diffuser on my flash, but I can see benefit to larger ones like those Lightspheres. I haven’t used one personally though.

If you are interested in sending me a question, check out my contact page for a way to send me an email!

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