AF vs. MF on Dig Reb XT

[AirCanada 0]

Does everyone go with the manual focus setting on the rebel?

Or are some people using the AF (continuously focusing w/ the bite switch plugged in) mode?

If in manual mode, do you use some gaffer's tape or equivalent to "keep" the focus setting? (I notice that the focusing ring is somewhat loose, or easily moved)

It appears on my camera (kit lens) that the 10ft - infinity focus is achieved when the ring is backed off a fraction of a turn from the stop at the long focus end. Intuitively, I would have thought that it would be all the way to then end of the focal adjustment...

[yuri_base 1]

Yo!

With a wide-angle lens, definitely go with the manual focus. The thing is, for wide angle, the hyperfocal distance is quite short. (hyperfocal is the distance from the half of which to infinity all objects appear sharp withing the circle of confusion, which is the maximum accepted unsharpness for your intended use of the photo.)

The marks on your lens are approximate. The real infinity focus depends on temperature and lens/camera calibration.

If you really want to learn the technical side of photography, you may want to check out the forums at dpreview.com. Here, there doesn't seem to be much useful techinical info.

Yuri

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[NSEMN8R 0]

I shoot auto-everything on my xt.

I've read about and experimented with all that av/tv/hyperfocal/... shit, but after 2 years with this camera it still takes its best pics when I let it figure all that out for itself.

[Faber 0]

that would be as you use it wrong then

try set your shutter speed as 320 for cloudy days and 500 on sunny days(in TV mode).

Bear in mind if you use a Pol filter which you should do,that it can make the stills slightly darker.

I NEVER use any auto functions(besides AF) on my stills cam unless i use flash,at that point i usaly use P

Also rember to adjust Parameter,ISO and WB for the shooting job/conditions

Stay safe
Stefan Faber

[NSEMN8R 0]

Quote

that would be as you use it wrong then

try set your shutter speed as 320 for cloudy days and 500 on sunny days(in TV mode).

Bear in mind if you use a Pol filter which you should do,that it can make the stills slightly darker.

I NEVER use any auto functions(besides AF) on my stills cam unless i use flash,at that point i usaly use P

Also rember to adjust Parameter,ISO and WB for the shooting job/conditions

Stay safe
Stefan Faber

Or just put it on the little green box and it will take care of all that stuff for you.


I just did what you said. It's sunny out. I took a pic out my back door on TV 500 and again on Auto. The differences are very very minor (at least on the computer. I didn't print them). If anything I'd say the one on full auto has better color.

On Auto it picked 500 for shutter speed also. but the aperture on Auto was at 16 and on TV it was 10. The iso on TV500 was 200 and on the green square it picked iso400.

That's an awful lot of variables to think about for the little tiny bit of difference in the pics. And like I said, if one is better I think it's the one taken on full-auto.

I guess that's why we spend all that money on technology. Thanks to the good folks at Canon you don't have to be a photographer to take nice pics. Even a regular skydiver like me can do it.

In fact, as I look at these 2 pics it makes me wonder why I spent all that time reading about all this AV/TV/ISO.... I could have saved the limited free space in my brain for something useful like porn and stuff.

[AirCanada 0]

Ummm....

To Clarify, I was asking about the use of AUTO FOCUS vs. MANUAL FOCUS functions... not full or partial auto or manual shooting modes.

The FOCUS mode is something you can choose, irrespective of the SHOOTING mode that you are in.

MANUAL FOCUS offering no shutter delays if the camera needs to re-adjust it's focus, or is having trouble focusing on the subject.... but potentially leading to more blurry shots.

AUTO FOCUS offering continual focusing on the subject(s), but potential delays in shutter release, due to trouble focusing on moving subjects, back lighting, etc...

[pbla4024 0]

Go with MF, focus on hyperfocal distance. With crop factor 1.6 you will have bigger DOF then with full frame cameras.

Fido

[Faber 0]

Quote

the aperture on Auto was at 16 and on TV it was 10. The iso on TV500 was 200 and on the green square it picked iso400.

it kind tells it self right..

Higher ISO allows higher shuterspeed or aperture

The difference is that on your slow shutterspeed whith low ISO your outcome will not be as good in big size as in small size.Why?

The higher ISO add´s more noice to your picture,meaning supersizing your pic you´ll see "dust" in your blue sky.
Also that slower shutterspeed(now i dont know how slow it were) can make that cool looking freefly suite look unsharp as it might move too fast that the cam can capture it.

That said i ALWAYS take my digi stills through Phothoshop,simply to add more contrast,making the stills even more powerfull,theres an function(yeah your loved AUTO) that takes care of ALL thouse stills from the same session.

Quote

Thanks to the good folks at Canon you don't have to be a photographer to take nice pics. Even a regular skydiver like me can do it.

nah its made for thouse that dont care about medium or top preformance..

Quote

I could have saved the limited free space in my brain for something useful like porn and stuff.

aslong you dont start shooting stills of that,then i think its a good idea

Stay safe
Stefan Faber

[Faber 0]

psst look at the post i responded to sorry i/we hijacked your tread

For skydiving i would go for MF,if that answeres your Q

Stay safe
Stefan Faber

[tonyhathaway 0]

Auto focus, or auto everything is great if you want the camera to deterrmine how the photo will come out. at least with manual you can put your subject out of center and get the image YOU want. Cameras today will shoot a great photo on full auto. Again, it shoots what it sees and determines what it thinks best. If you play around with some manual setttings, you may find that you ruin a lot of photos learning, but in the end they will come out just like you plan before you go up. Usually better than auto-whatever. auto has itl place at times, but not always.
-Tony

My O.C.D. has me chasing a dream my A.D.D. won't let me catch.

[AndyMan 7]

For a long time I bought into the standard advice given by (seemingly) everyone, which was to shoot manual focus.

I did that for a while but got very frustrated with shots that were out of focus. This makes sense - since we generally take shots from different distances based on what we're shooting - tandem, vs 4way, vs 20 way, vs freeflying. I never managed to keep straight the different focus settings from the different distances.

I switched to auto-focus, and am generally happy.

I go back to manual focus in a few cases, most of which are the few cases where it's important to get a good exit shot. Tandems are a great example of this. Shooting exits is tough in auto-focus mode since the camera will lock onto the plane instead of the jumper, and it'll get confused.... it simply won't take the shots on exit. I shoot tandems in manual focus. I imagine I would also shoot balloon exits manual, for the same reason.

_Am

__

You put the fun in "funnel" - craichead.

[velocityphoto 0]

I'd hate to screw up an awsum balloon shot because i was using auto focus! Specially since someone is usually paying my slot and want good video and stills for the office wall....

A friend will bail you out of jail , a REAL friend will be sitting next to you in the cell slapping your hand saying "DUDE THAT WAS AWSUM " ................

[AndyMan 7]

Quote

I'd hate to screw up an awsum balloon shot because i was using manual focus!

I understand that sentiment... but how do you deal with the time it takes to focus? The delay on the first shot seems to rule it out, for me. Do you use USM lenses? There's nothing worse than hitting the shutter release only to hear the AF searching!

_Am

__

You put the fun in "funnel" - craichead.

[velocityphoto 0]

I meant because i used auto focus, sorry !

A friend will bail you out of jail , a REAL friend will be sitting next to you in the cell slapping your hand saying "DUDE THAT WAS AWSUM " ................

[MrHips 0]

Hi there AirCanada

A couple things you might want to mention before the experts give you their opinions.

Firstly, what is the lens you are using? If you are using the standard 18 - 55mm the AF motor is very slow and isn't really useable. However using a lens from Canon with a Ring USM Motor will certainly be fast enough. Assuming you use the 'Servo Mode' for focusing. Generally the shorter the focal length of the lens (EG 15mm as opposed to 50mm) the greater the depth of field. So the focus motor doesn't usually have to move much anyway. You can have a look at the scale on the top of the lens you have to get a rough idea of it's depth of field without having to do a complex calculation to work out the Hyperfocal Length for your lens. Have a look at the Infinity symbol and then look at the number closest to it. It might have a 1 next to it. Thats means that when you set the manual focus to this 1 mark, everything from 1m (or foot depending on the scale you look at) to infinity should be in focus (I mostly use a Canon 10-22mm USM lens for freefall work and this is the figure from it's scale). In reality that method of manual focus setting isnt always perfect but in most cases it works. This will also explain that an AF Motor will only have to fine tune the focus within this range also, again with wide angle lens's only a short movement is req'd and performed quickly with a Canon ring USM lens (or Sigma HSM lens)

Secondly if you want to make sure that multiple subjects are in focus (as one person mentioned exit shots) make sure your focus points are set appropriately. Thats the little red dots in the viewfinder that light up before you take the shot. There is no point in having the centre focus point selected as the only focus point if you are framing a diving plane in the right corner and the tandem in the bottom left corner or centred for that matter. Because you are forcing the camera to focus on one point (or focal plane) or another. Hope thats makes sense. I get a 1/100 out of focus failure rate. Considering with these camera's it is easily possible to take over one hundred frames from 14'000ft I dont think your going to have a problem missing too much!

[AirCanada 0]

Thanks!

Very Helpful.

[Billy 0]

I found with the kit lens trying to get anything on manual focus was a joke... Like you said it is loose, and moves enough even with tape to make this difficult. Leave the tape on one time and you can burn up your servo after switching back to AF.

I had much better luck with the AF and using a small appeture if light allows, and flying to maximize what light you have...

Ultimately dude,, ya wanna spend some money on a good lens

Natural Born FlyerZ.com

[pcalandra 0]

Nice & informative post the way MrHips!

I've actually found that autofocus worked pretty well for me in most situations using the standard kit lens a 300 in TV setting, 1/500 of a second, ISO 200 or 400 depending on the light. Pretty much the same with the Sigam 18mm I had.

When I use manual focus I find using a rubber band to around the lens to hold my focus setting works well for me. By the way I did the same thing for focal length on the zoom. Even gaffers tape will eventually leave some residue on the lens. As far as the AF/MF switch goes I never had a problem with it, it's hard to move by accident in my opinion, howhever you could tape it, or again add another ruber band.

I just received my new 350D today with the Canon 10-22mm USM and I'm anxious to see hwat works best with that combo.

[boyfalldown 0]

Wading through the replies on here I see (what seems to me) A lot of good information, but one major piece is missing. The lens you use has a lot to do with how well AF or MF will work. The kit lens has a somewhat external focus. When you rack the focus the front of the lens rotates and the lens gets longer or shorter. Even with a lot of gaff tape and rubber bands holding it in place, with just a little pressure on the face of the lens the front (rotating) objectives push back just a touch resulting in different focus from what you set on the ground, resulting in inconsistent pictures. In that case AF may be better for sharp pictures, but the down side is delay when the camera searches for a focal point, possibilities of hunting, and the camera picking the wrong subject to focus on altogether. The second type of lens would be an internal focusing lens, one where the front element does not rotate, and the lens does not get longer or shorter when the focus is changed. This is the type of lens I use and recommend for skydiving. One small bit of gaff tape will hold the focus ring in place, and no amount of pressure on the front of the lens will affect focus, great for high wind environments. In this case you get the best of all compromises, good consistent focus with no waiting.

Just as a side note, I use a Tokina 17mm Pro ATX lens. It has a clutch for the focus motor. if you slide the focus ring forward or back it engages and disengages the focus motor and the manual drive ring. I set it for manual focus, set infinity (the sideways 8) at F11 and disengage the manual focus ring, which engages the motor, but since the AF is off it locks the focus in place with no tape or worries of moving the focus ring and changing focus. Also the lens is really square, there is almost no noticeable barrel distortion that is often found in lenses this short for the same price ($389)

[DancingFlame 0]

Quote

It appears on my camera (kit lens) that the 10ft - infinity focus is achieved when the ring is backed off a fraction of a turn from the stop at the long focus end. Intuitively, I would have thought that it would be all the way to then end of the focal adjustment...

It's common feature of most AF lenses (excluding macrolenses withount infinity). It is required for AF system to focus on infinity. Setting focus ring behind infinity mark will cause lens to focus 'beyondTheVoid' - behind infinity.

[bmcd308 0]

>>infinity focus is achieved when the ring is backed off a fraction of a turn from the stop <<

Necessary for the lens to achieve infinity at all temperatures.

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