DoF Preview

Folks,

I just received an 85L f/1.2 (work's not mine). I noticed that the out-of-focused objects came out more blurred in my image than in my viewfinder. Playing with the DoF preview button I noticed that I have essentially no intensity change in the viewfinder wider than about f/2 (even though I can see the leaves of the iris closing - and a beautiful mechanical device it is). Is the problem the relay optics in the viewfinder? If the optics along that path are f/2 then I guess I will never see a proper preview faster than f/2? The body I was attached to was a t2i btw. Do other bodies have faster viewfinders?

Of course, there's always live view and that's how I plan to use it in the project I purchased it for. Actually, live view x10 piped through HDMI to a 30" television. That's my focus mechanism :). I was just hoping to get a better sense for the object-to-background blur in the camera image as I am composing.

You should use a different type of focusing screen for fast lenses. The standard is not good enough and it leaves you hanging from f2.8 down or so.
Please take a look at this video: http://www.youtube.com/watch?v=fYGjEnm8PSc

Jan

@Sheiky Thanks! Exactly what I needed. So what happens if I leave a precision focusing screen in there with a lens that's not faster than f2.8? Will the image just be dark?

Sheiky--would a Katzeye focusing screen work well for him?

The precision screens are ok at f/2.8, pretty dark by f/5.6 (hard to use indoors).

FWIW, Live View will show the true DoF.

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Originally Posted by neuroanatomist

FWIW, Live View will show the true DoF.

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yup - acknowledged that above. I just find composing hand-held shots with live view is not pleasant.

So if all my lenses are f/4 or faster I should be reasonably ok with precision screen it sounds like. A good excuse to upgrade the 700-200 from f/4 to f/2.8!...

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Originally Posted by ChadS

So if all my lenses are f/4 or faster I should be reasonably ok with precision screen it sounds like. A good excuse to upgrade the 700-200 from f/4 to f/2.8!...

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I used the 70-200 f/4 all the time indoors with the precision screen and personally I didn't mind the darkness, but I think a lot of photographers really would dislike it a lot. (Some even upgrade to full frame in part for the brighter viewfinder.) But don't let that stop you from getting an f/2.8. :)

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Originally Posted by Sean Setters

Sheiky--would a Katzeye focusing screen work well for him?

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I hadn't heard of them before, but I see my local shop now has them as well. In theory they seem like the perfect deal especially if you're using multiple lenses with different max apertures(higher and lower than f2.8). However they are steep priced compared to the Canon focusing screens. They cost more than 1/3rd of a Canon t2i here:confused: I would almost be crazy enough to say to buy a second t2i with a different focusing screen just for fast lenses:p

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Originally Posted by Daniel Browning

I used the 70-200 f/4 all the time indoors with the precision screen and personally I didn't mind the darkness, but I think a lot of photographers really would dislike it a lot. (Some even upgrade to full frame in part for the brighter viewfinder.) But don't let that stop you from getting an f/2.8. :)

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I do mind indeed. With the 50mm prime it's awesome, but with my two other lenses 24-105(mostly used) and 70-200 f4 it's just too dark for my likings. That being said, having AFMA and knowing that my 50mm focuses spot on is easier to work with IMO than a darker viewfinder.

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Originally Posted by ChadS

yup - acknowledged that above. I just find composing hand-held shots with live view is not pleasant.

So if all my lenses are f/4 or faster I should be reasonably ok with precision screen it sounds like. A good excuse to upgrade the 700-200 from f/4 to f/2.8!...

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I find the composing with live view is much easier with a monopod. If that is feasible, you may want to give this a try. When I use my Lensbaby Composer (a very dumb MF only lens with no electronics), I find a monopod and live view makes is much easier to use.

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Originally Posted by Sheiky

I would almost be crazy enough to say to buy a second t2i with a different focusing screen just for fast lenses:p

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Another perfect excuse why I need to upgrade my body AND my lens... (somehow I don't think my wife will buy this argument). I don't think I'd be interested in a full frame unless it was body #3 (assuming I keep the T2i as a backup). I shoot 90% sports or children playing so frame rate is king. Sure I wouldn't turn down a 5D II but I wouldn't buy one. Now, the 1DX does everything I want in a camera - somehow I don't think the misses will go for that one either.

In terms of shooting with the 85L f/2.1 I doubt I'll use it much. It's going to get incorporated into an experiment and stay there. I was just doing some ... testing - you know, to make sure the lens works and all that... (even though it's going to get parked at minimum focal distance and set to manual focus for the rest of its life).

Thanks for the info on the screens. That's good to know regardless.

Glad to help out a little.
To be fair I shoot a lot of action and sports-related stuff and I never felt that the 5D2 was holding me back. I could use a faster frame rate from time to time, but it simply rocks in other things. When I compare it to my girlfriends 40D I don't get regrets on buying a 5D2...even for sports.

About the 85mm f1.2L. The testing you did was very good. You have to realise that it ages faster if you don't move it around. It needs at least 1 hour per week AF-training to keep the lens in good shape. The last thing you want is to have it turn into one piece of big heavy bulky glass...keep it in shape! I also know a good training and rehabilitation center in the Netherlands if you can't get the job done yourself. Just PM me for the adress:o

Mind you, your 5D2 shoots ever so slightly faster than my T2i so I guess we're even in the frame rate department. However, if I were going to pay several kilodollars for a new camera I'd more likely buy a 7D ahead of a 5D2. Of course, The 1D4 would be the one I'd blow a lot of cash on shy of having a 1D-X land in my lap.

I've got to set up an auto-focus test stand. It appears the 85 is front focusing by quite a bit on my T2i. Lacking any AFMA I doubt I'll be able to 'test' it very much - at least not below f2 or so. But as I said for my (work) purposes it'll do just fine.

In frame-rate we do equal out, however the shutterlag of the t2i is a lot slower and therefor a lot less practical for sports. IMO shutterlag has a much larger impact on your keeper-rate than the frame-rate does.
To be fair the 1DX seems to be the ultimate camera for me, however I'm still very happy with the one I got now :D
PS: I'd rather get 2 50D/40D's than 1 7D. I used it twice now and seen some results from a friend and it might be coincidence, but that thing has a very soft output. And I don't really like sharpening every single shot.

As for the 85mm focusing. At f1.2 the DOF is so shallow that you might prefer live-view anyway for most of your shots. Have fun;)