DoF Preview

[ChadS]

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.

[Sheiky]

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

[ChadS]

@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?

[Sean Setters]

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

[neuroanatomist]

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

[neuroanatomist]

FWIW, Live View will show the true DoF.

[ChadS]

FWIW, Live View will show the true DoF.

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!...

[Daniel Browning]

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!...

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.

[Sheiky]

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

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

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.

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.

[ChadS]

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

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.