silly question, does lowest f affect a lens at other f settings?

[miketoll]

Always turn the camera off when changing lenses so there is no electrical charge to attract dust. I always put the wind on my back too and mostly point the camera down. So far have only needed the Rocket blower except twice have needed tweezers to remove a hair that nothing else would pick up. It was not actually touching the sensor but attached at one end to the box and floating about at the other end in front of the sensor. Heart in mouth, take glasses off for better and closer close up vision, hold breath, remove hair and then let out huge sigh of relief. Having a household full of pets does not help!

[Birdsnapper]

Originally Posted by Don Hoey

Sorry Mike but I do not understand this. Using a fast lens at wide apertures can isolate the subject from the background as in the attatched pic. Hyperfocal distance immaterial.

No more milky waterfalls ??? Just stop the lens down.

Chris,

I will look for my 400mm dof tables and draw up a chart so we can all understand your situation as it relates to your post 1.

Don

PS : Decent engraved dof scales are something I miss on modern lenses. My old AIs stuff is good for that.

Don, I presumed that Chris's query about f2.8 and taking pancakes flat on related the limited DOF associated with large apertures- hyperfocal distance is therefore useful when needing large apertures and maximum DOF.

My remark about milky waterfalls was just a friendly jab at Chris (Chris, if you read this, then well done for not rising to the bait).

[Don Hoey]

Mike,
Most of my lenses are old M/F jobs with nice dof engravings so quite easy to determine hyperfocal focussing. Kind of forget that other than Joe, probably all members here are full A/F users. Relavence of that in my PS about poor dof markings on a lot of A/F lenses. Stevies zooms have no markings at all. ( Perhaps I am showing my age. )

Mind you with the 400mm dof is so limited that the lens is only engraved for f22, insufficient space for any more lines no matter how fine.

Don

Thank you again folks. Returning to CinC, I notice that it was 'circles of confusion' that I was confusing with hyperfocal distance.

I didn't say any more about waterfalls as I was pleased the message had got through Mike. Now onto feather fluff.

[Tannin]

Originally Posted by Don Hoey

Kind of forget that other than Joe, probably all members here are full A/F users.

Oh, i don't know about that, Don. I use MF for landscapes from time to time and birds ocassionally, for macro quote often, and for 100% of shots with my tilt-shifter (which is MF, obviously). I'm guess that (TS/E aside) many other members here do too. One thing I often do, however is "cheat" by AFing on a point of interest somewhere off centre, then flicking the AF/MF switch to MF, compose and shoot. (I pretty much always use centre point-only AF; this method seems quicker and easier than fiddling about changing AF points, or just focusing by eye in the first place.)

The main gotcha with this method is with the 10-22mm lens. With anything longer, if you forget to turn the AF on again before you put the camera back in your bag, you see right away when you take it out again, but the DOF on the 10-22 is so large that through the viewfinder you can simply not notice that it's nowhere near focused. It's only when you look at the results on the big screen that you realise what a dumb mistake you made!

EDIT: this was one good thing about the mini-cement mixer focus motor in my old 18-55 kit lens: because it was so loud, you couldn't miss noticing that the AF motor wasn't doing anything. With these high-tech fast, quiet USM lenses, if there is a little bit of breeze or the birds are calling, you can't hear them!

[Gidders]

Originally Posted by Tannin

The main gotcha with this method is with the 10-22mm lens. ....but the DOF on the 10-22 is so large that through the viewfinder you can simply not notice that it's nowhere near focused.

I tend to use my 10-22mm on MF as well ... set it on 10mm f8 focused at 1m and everything from 0.5m - infinity is in focus

Away from web for a week, so thank you to all contributors to the thread.

Pleased you are still lurking somewhere there Clive.

[Joe]

Kind of forget that other than Joe, probably all members here are full A/F users.

I'm getting there Don
.....I have a sigma 15-30mm wide aoom..would value AF on my 180mm and 300mm particularly. justification is always key for me. The switch to digital was only made more palatable by getting more than expected for some old film cameras.(collectable!...were they really that old LOL)


Back to the original posting....There is also an advantage with faster / wider max' aperture lenses when relating to AF......tele /zooms particularly. A 80-200 f2.8 will normally be faster at focusing than a 80-200mm f4-5.6 for example, especially in low light conditions. This due to the camera AF sensors getting more light. It's not as obviuos with entry level digi bodies, but once you get to mid range and pro models the speed is quite noticeable.