Lens rental question 85 f1.8 vs 100 f2.8

The second Saturday in august one of my friends wants me to shoot her engagement photos and the third Saturday another friend wants me to do a couple shots of their wedding on top of the person they paid to do it because they like my work. Now honestly weddings and portraits are not really my thing and I was going to rent a lens to do this I have been considering the 85 f1.8 and the 100 f2.8. The 85 because it has a good reputation as far as I have seen on this site for portraits, and the 100 macro because if I am going to have the lens for two weeks I would really like to get a feel for this lens in regards to macro work because it’s one that I have on my list to buy, and I have seen several people say it makes a good portrait lens as well. The engagement shoot will be done outside at a gardens area and the wedding the only pictures that I think they want me for sure to take are after the wedding outside by a lake on the grounds of the church. If I am going to take pictures at the reception (indoors) it will be with my 50 and flash. I don’t want to go to crazy with the rental because I am trying to save up for gear that I really want so please no 85 L’s or anything that is going to break the bank but I am up to other idea’s. But basically do I go for the sure thing that I am not really interested in or do I go for the lens that I want to buy in the future that I know I will have fun playing with in between the 2 shoot. Am I being selfish? PS Sorry for the long winded post.

I've just used the 100 f/2.8 at a school sports day event and for portraits it performed beautifully. I used a max. aperture of f/3.2 and achieved really nice bokah. See here for a comparison of IQ between the 85 and 100 set to f/2.8 (http://www.the-digital-picture.com …&CameraComp=9&F​LI=0&API=2). The 100 wins it for me, even though it's wide open at this aperture. One thing though, you need plenty of space for good full length shots - I had an entire sports field!

Thanks for the link pcook! I was thinking that I was going to have plenty of space to work with since almost all of my shots are going to be outdoors. I might just have to rent the 100 because I am going to be getting Kenko Tube set this week end and would love to see what they can do on this lens.

I have the 100 and I find it slow to focus. I'd probably go for the 85.

I was afraid someone was going to say that
It was one of my concerns about going with the lens, how slow is the lens? Is it worse it low light and better in bright light. Or maybe a better question so I can understand how slow it really is: Is it slower than my 70-300 IS? I hope someone can compare.

I've had both and found the difference in AF speed indistinguishable when the focus limiter on the 100mm is set to .48m

It's really just a 1.8 vs Macro Capability question. Only you can decide what you need.

I find the 100 slow only when there is a very large difference between its current focus position and the new position e.g. from macro to infinity. Otherwise, it focuses quickly. At a wedding, you are going to be focusing on subjects at similar distances from the camera. I had no problems with focusing the 100 for my subjects (much faster and more accurate than doing it manually). I guess either the 85 or the 100 will be excellent for the wedding. The 100 will be awesome for your macro experiments.

Ya know I've been thinking about your question here for a while...
I'd be curious to see what those in the wedding fourm have to say as to how useful the AF speed is on the 100 2.8 macro vs. the 85 1.8 at an outdoor wedding.

To me, many of the posts in the wedding forum that talk about lens choice seem to focus on max aperture and focal length. Speed of AF, I guess is discussed, but it doesn't seem to register in my mind as being a major issue in many of the posts. I may be glazing over those posts though...

I'd suspect a wedding photog would choose the 85 1.8 over the 2.8 macro for the primary reason of more light gathering/better bokeh opportunities afforded by the wider max aperture. Throw in the fact it seems to focus faster than the 2.8 macro, plus it is cheaper, and you probably have all the reasons why it's a widely used lens in the wedding world.

That said...I agree with others that say only you will be able to determine if speed of AF b/w the two makes a difference for you. Many wedding photogs use the 85 1.2 even though it supposedly has a slow AF mechanism...thus personal preference certainly comes into play here.

I have shot several weddings as a 2nd shooter (no pressure !) and I have yet to use the macro for anything but pre-ceremony ring shots. But I wouldn't hesitate to bring it out if I needed/wanted to.

You'll probably enjoy using both at the event, but you'll really love the macro with tubes on it for your personal macro photography...

Have you considered renting the 17-55 2.8 IS for these events? Seems to be a wildly popular lens on a crop body like yours. I've read posts from wedding photogs that they could shot 90% of a wedding with that lens. IQ would be better than your 50 1.8 for your indoor portion. Then coupled with either your 85 1.8 or 100 macro you'd have a wider focal range covered for your outdoor shots.
Would like to hear how it turns out for you and see any images from your events!