Today is a big day for me, I am going to learn..

AnimalRights

http://www.usa.canon.com/dlc/controller?act=GetArticleAct&articleID=2286

Back-Button Auto Focus!
Which in turn is similar to compose/recompose?

any other tips to add to this feature?

I will be praccying on a pint on a table.

Morrisseeee

I will be praccying on a pint on a table.

looks like you've already had one or two too many

FoxT

I use Backbutton AF almost all the time now, for sports, street,portraits etc. I don't claim to be any good at these things - but I have found that it works waaayy better for me in almost every situation - unless

- Aperture is f/4 or smaller
AND
- you want to grab a shot very quickly

Advantages of BB
- Sports - you give the AF a headstart before you shoot. Even if it is only a half a second it seems to help my 'in -focus' hit rate
- f/2.8 or wider - Using BBAF ensures that you focus specifically on the exact point you want to be in focus. I found I pretty much have to do this all the time at wide apertures.

Go for it, show the results!

-FoxT

mrmac

I use this feature on a D300, where I've used the AF-ON button for continuous AF. It's great for sports shots, and wildlife that moves around a lot. When trying to get shots of moving objects, you can be panning and moving with the subject; trying to keep the shutter button half-pressed, without accidentily pressing fully down, was a pain.

Using the re-programed button means I can keep my thumb fully pressed down, and press the shutter when needed. May not suit everyone, and indeed takes a bit of getting used to, but I like it.

pete4130

I don't see why anyone wouldnt use it in the majority of instances. the moment I switched to nikon from Pentax 7 years ago I started using it. Its not that it makes it easier to focus/recompose alone, its the fact it can free up the shutter for "release priority" so that shutter will release even if the focus area in the viewfinder isn't focused (after recomposing) and the shutter releases every time you hit it.

The only time I don't use BB focus and shutter release priority is when shooting handheld macro. I switch to regular focus and put the camera on focus priority so when I am creeping with my lens to focus the camera fires instantly when it recognises that the subject is in focus.

AnimalRights

mrmac wrote: »

When trying to get shots of moving objects, you can be panning and moving with the subject; trying to keep the shutter button half-pressed, without accidentily pressing fully down, was a pain.

I had prefected this at gigs and it wasn't a big problem.

FoxT wrote: »

I have found that it works waaayy better for me in almost every situation - unless

- Aperture is f/4 or smaller
AND
- you want to grab a shot very quickly

Why does it not work as well on aperture of f/4 or smaller? Actually f2.8 is higher or lower? I call it lower altjough not 100% I always get that bit back to front.

sheesh

AnimalRights wrote: »

http://www.usa.canon.com/dlc/controller?act=GetArticleAct&articleID=2286

Back-Button Auto Focus!
Which in turn is similar to compose/recompose?

any other tips to add to this feature?

I will be praccying on a pint on a table.

never knew that existed. I can see loads of applications for it. Thanks.

sineadw

sheesh wrote: »

never knew that existed. I can see loads of applications for it. Thanks.

Me neither! Will be giving it a go

Borderfox

Tried it a couple of times but cant get used to it.

smelltheglove

AnimalRights wrote: »

I had prefected this at gigs and it wasn't a big problem.



Why does it not work as well on aperture of f/4 or smaller? Actually f2.8 is higher or lower? I call it lower altjough not 100% I always get that bit back to front.

I think 2.8 is higher as it is the largest opening whereas 22 would be low.

mrmac

AnimalRights wrote: »

Why does it not work as well on aperture of f/4 or smaller? Actually f2.8 is higher or lower? I call it lower altjough not 100% I always get that bit back to front.

I think FoxT means f4 or larger, i.e. f2.8 (smaller number)?

I'm guessing what FoxT is referring to, is that continous AF can be awkward at this aperature, due to the shallow depth of field, so keeping the focus on the subject of interest can be difficult.

Sorry FoxT if I've got this messed up???

Valentia

Higher and lower makes no sense in this context. Smaller and larger makes more sense. To me anyway. (Or wider and narrower even).

stcstc

is the reason is doesnt work on higher than 5.6 to do with the focus points

i think only the centre focus point uses 2.8 or somethin, i seem to remember reading that somewhere

Borderfox

AnimalRights wrote: »

I had prefected this at gigs and it wasn't a big problem.



Why does it not work as well on aperture of f/4 or smaller? Actually f2.8 is higher or lower? I call it lower altjough not 100% I always get that bit back to front.

I would presume that the depth of field gets narrower and this makes it more difficult especially in low light

sineadw

Ah - it's the same button as the AE lock on the Mark I. That's why I never used it. Hmmm... Wonder if it's customisable.

Ballyman

Borderfox wrote: »

Tried it a couple of times but cant get used to it.

Perserverance. Once you get used to it you'll wonder how you ever operated the camera without it!!

FoxT

- Aperture is f/4 or smaller
AND
- you want to grab a shot very quickly

Firstly - the aperture is the hole in the lens that lets in the light. A smaller aperture, therefore, has a higher f/ no. So, f/5.6,f/8 etc, are SMALLER than f/4.

I find that if I try to grab a shot at a wider aperture (f/2.8,f/1.8) the focus is not always spot on if I do it quickly. I don't think its a camera fault, 'cos I have tested it - but if I am taking a shot really quickly then I dont have time to think about & select the exact point of focus. So I generally keep the lens at about f/4, which gives sufficient depth of field to compensate for this.

if I go around grabbing shots really quickly at f/2.8 or wider, a lot of them aren't focused exactly on what I wanted. hope that makes sense...

-FoxT

pete4130

It doesn't matter what aperture you have your lens set to when focusing. It stays wide open until you release the shutter and only then does it close down. the wider your aperture the more light that comes in and the easier the camera should find it to focus.

When focusing and recomposing at wide apertures you can move out of focus as you recompose as you are slightly changing to distance between the focus point and the sensor plane.

Also if you focus and recompose at wide apertures/wide open and the focus point is now towards the edge of the frame it will naturally be softer (especially when wide open).

The only lens I find this noticeable on is my 50mm 1.4 though and somewhat on my 85mm 1.8.

It also depends on how good the lens you are using at the time.

gloobag

Be sure to set this option up in your favorites menu on the camera for quick access. That's where I have it, along with mirror lock-up, bracketing, sensor cleaning etc. . .

I love the custom menu

By the way, I have a focusing/metering question specific to the 5DmkII, maybe someone here knows the answer.

If my metering mode is set to spot, and I manually change the focus point from the center to one of the corner points for example, am I now metering from the new focus point, or the center? can't seem to get a clear answer to this anywhere online

pixbyjohn

gloobag wrote: »

Be sure to set this option up in your favorites menu on the camera for quick access. That's where I have it, along with mirror lock-up, bracketing, sensor cleaning etc. . .

I love the custom menu

By the way, I have a focusing/metering question specific to the 5DmkII, maybe someone here knows the answer.

If my metering mode is set to spot, and I manually change the focus point from the center to one of the corner points for example, am I now metering from the new focus point, or the center? can't seem to get a clear answer to this anywhere online

I would say you are metering from the highlighted spot which will be the corner point you have chosen.

AnimalRights

Ok, didn't get to a pub (with proper light) to praccy til 3...
With my assistant and my copies of that link I learned to use the BBF and compose/recompose, I know it was a very set set up but still...
I hope when I'm out next to put it into proper practice.
I also learned and now understand how people just use to hold the Camera at any angle in the air/at the hips (sly photos!) to get a shot!
TY for all help too in this thread, I should also bookmark it as my memory is terrible.

wersal gummage

gloobag wrote: »

If my metering mode is set to spot, and I manually change the focus point from the center to one of the corner points for example, am I now metering from the new focus point, or the center? can't seem to get a clear answer to this anywhere online

couldn't you check this by trying it with an object with two different colours - or one part of the object in the shade ?? spot meter off a side point on the shaded object (leaving the centre point aimed at part of the object thats not in the shade) and the results should be obvious ??????

sprinkles

pete4130 wrote: »

Its not that it makes it easier to focus/recompose alone, its the fact it can free up the shutter for "release priority" so that shutter will release even if the focus area in the viewfinder isn't focused (after recomposing) and the shutter releases every time you hit it.

+1 This is the biggest advantage imo.

Roy Rogers

Interesting, gonna try this out this evening I think.

eas

pete4130 wrote: »

I don't see why anyone wouldnt use it in the majority of instances. the moment I switched to nikon from Pentax 7 years ago I started using it. Its not that it makes it easier to focus/recompose alone, its the fact it can free up the shutter for "release priority" so that shutter will release even if the focus area in the viewfinder isn't focused (after recomposing) and the shutter releases every time you hit it.

I agree about freeing up the half press function, but why not use afc which defaults to release priority, then you can use shutter half press for something else?

Horses for courses and all, but I have my half shutter press set up for exposure lock.

pete4130

I have it to AFC as well. On my camera you can still set the priority on the shutter release button as well. so it can be AFC, BB focusing and focus priority!

AnimalRights

eas wrote: »

I agree about freeing up the half press function, but why not use afc which defaults to release priority, then you can use shutter half press for something else?

Horses for courses and all, but I have my half shutter press set up for exposure lock.

I have mine set to this now so I can't use the half shutter for focus.

"2: Metering start / Meter + AF start

Back-button AF activation. Shutter button no longer activates AF, but of course fires the shutter. Metering is continuously updated — if you shoot a sequence of pictures, the camera takes a fresh meter reading for each one. There’s no locking of exposure, unless you separately press the AE Lock button"

and eas AFC?

AnimalRights

Another question for Pete or someone..
Am I right in thinking that I've finally realised that to get a picture of 2 people in focus that its easier if I shoot not wide open and instead drop down to around 5.6?
Cos normally I do have problems at times if obviously one person is slightly more forward on the plane that one of them does be oof.

AnimalRights

Borderfox wrote: »

Tried it a couple of times but cant get used to it.

Pity ur not a games player but I play lots of FPS (1st person shooter) games on my PC and obviously once I got used to mapping out my keyboard for game movements it became 2nd nature pretty quickly because I play a lot, same thing can be said to Photographers, they shoot a lot (pun!) so it quickly should became 2nd nature.
I just picked my Camera out the bag now and straight away my hand went to back focus....good good!

gloobag

AnimalRights wrote: »

Am I right in thinking that I've finally realised that to get a picture of 2 people in focus that its easier if I shoot not wide open and instead drop down to around 5.6?

Yup, f8 would be a safer bet though.

eas

AnimalRights wrote: »

and eas AFC?

yeah, not sure what it's called on Canon - Continuous Servo AF?

AnimalRights wrote: »

Another question for Pete or someone..
Am I right in thinking that I've finally realised that to get a picture of 2 people in focus that its easier if I shoot not wide open and instead drop down to around 5.6?
Cos normally I do have problems at times if obviously one person is slightly more forward on the plane that one of them does be oof.

basically yes, but it depends on focal length and distance from subject ( DOF theory )

charybdis

AnimalRights wrote: »

Another question for Pete or someone..
Am I right in thinking that I've finally realised that to get a picture of 2 people in focus that its easier if I shoot not wide open and instead drop down to around 5.6?
Cos normally I do have problems at times if obviously one person is slightly more forward on the plane that one of them does be oof.

It depends on what kind of look you want. Most lenses are designed to focus on a plane parallel to the camera so that only one "distance" from the camera is in sharp focus. It is possible to extend the region of sharp focus around this "distance" by increasing the depth-of-field, which can be achieved by stopping down your lens.

If you're trying to get a photograph of two people in focus, you either need enough depth-of-field to render them both acceptably sharp, or place them at a uniform distance from the camera.

Alternatively, you could make use of the "tilt" function of a tilt-shift lens and place the plane of focus across the scene diagonally, although that'd probably by impractical for candid photography.

AnimalRights

charybdis wrote: »

Most lenses are designed to focus on a plane parallel to the camera so that only one "distance" from the camera is in sharp focus. It is possible to extend the region of sharp focus around this "distance" by increasing the depth-of-field, which can be achieved by stopping down your lens.

If you're trying to get a photograph of two people in focus, you either need enough depth-of-field to render them both acceptably sharp, or place them at a uniform distance from the camera.

This is interesting, is there another way or logic to explain/work out this 'sharp sweet spot'?

and Gloobag It would be impossible to shoot in dark places/pubs with f8 though.

charybdis

AnimalRights wrote: »

This is interesting, is there another way or logic to explain/work out this 'sharp sweet spot'?

and Gloobag It would be impossible to shoot in dark places/pubs with f8 though.

It's not really a "sweet spot" per se.

Typically a lens' "sweet spot" with regard to aperture would be the aperture value at which it produces the best (sharp, low chromatic aberration, low halation, etc.) image quality.

What you are talking about relates more to depth-of-field.

When you have two main subjects at different distances from the camera, you have to compromise on where you focus so that one or neither subject will be on the plane of focus. However, you can compensate for this by stopping down your lens or otherwise increasing the depth-of-field so that both subjects are in acceptable focus. If you are dealing with low-light situations and need to use larger apertures to attain the desired exposure you may need to extend the depth-of-field in other ways, for example: you can use a wider lens or stand further back from your subjects.

FoxT

This might take a while, bear with me. Suppose you see an Apple & an Orange that you want to photograph. They are spaced a little apart. There is no feature between them that you want to focus on.

http://lh3.ggpht.com/_QUZCzGXHyzw/S7PMCG4b9SI/AAAAAAAAJgM/bZU6vZ3003o/s400/step%201.jpg

So, you decide to focus on the apple. The pic above shows this. The orange line is the 'plane of focus'. Everything on this line will be in focus. Great, the Apple and the orange are on the line, so both are in focus. But - you want to recompose for some reason so you rotate the camera.

http://lh3.ggpht.com/_QUZCzGXHyzw/S7PMCeGuTXI/AAAAAAAAJgQ/6Uv4YeGinyk/s400/step%202.jpg

Now, as you turn the camera, you see to your dismay that neither the apple nor the orange are in focus. Yikes!

Ways to get around this:
This becomes a problem generally at very wide apertures (f/1.4 to f/2.8 or so), very short (2m or less) distance to subjects, and longer focal length (50mm or more) lenses.

Hope it makes sense..

-FoxT

FoxT

It goes without saying that you need a PhD in brain surgery to embed an image inline in a post. Arrrgh

ThOnda

I am focusing with my index finger more than 10 years and use thumb to lock the exposure for the same period. I know about that function but it confuses me every time I borrow camera from anybody with such settings.

Ballyman

AnimalRights wrote: »

and Gloobag It would be impossible to shoot in dark places/pubs with f8 though.

This is what flash is for! Allowances have to be made at times.

Do you have a flashgun? If you used bounced flash then you would probably get both people in reasonably good focus.

AnimalRights

I have a flash of course but I'm at the stage where I'm experimenting without it, I know about dumbing down the flash and all that...

When you back button focus how long will I get to keep shooting without having to focus again?
When I'm at a gig I'd like to obviously get away with more shots from the one AF lock...
I don't see any sign like you get when you AE.

Ballyman

AnimalRights wrote: »

When you back button focus how long will I get to keep shooting without having to focus again?
When I'm at a gig I'd like to obviously get away with more shots from the one AF lock....

Use AI Servo and keep your thumb on the back button focus. The camera will continue focusing while it is pressed no matter how many times you press the shutter or where you/your subject moves to.

If you use One Shot, then once the camera locks focus then thats it. If you or the subject moves then you will have to release the back button and press it again to re-focus.

I use AI Servo most of the time. The only time I would use One Shot is when I'm 100% certain that neither the camera or the subject is going to move, which in my case is when the camera is sitting on a tripod pointing at a mountain! Every other time it's set to AI Servo.

AnimalRights

Ok they're the type of simple answers I like!
I only use 1 shot when I'm praccying on my pint in the pub and I know It won't move.

So basically I have to keep my button on the BBF button..

Ballyman

AnimalRights wrote: »

So basically I have to keep my button on the BBF button..

Finger.

And yep.

AnimalRights

So after a few days now I can safely say I've found another massibe advantage of back button focus..I hardly get any OOF pics now! Amazing, obviously when I used the shutter and did part 2 of the full press I was shaking the camera! Now when you just use the BBF you don't interfere with the Cameras movement unlike the shutter which you do.
Loving the BBF totally btw.

Heebie

Pentax K20D can also do this. There is and AF button next to the exposure compensation button for the right thumb on the back right of the camera... works similarly. I haven't tested it enough to find out if you have to keep it held down while you recompose your shots. (although performing focus, then switching the auto-focus lever into manual should accomplish that if it's needed.)

Dimy

Thanks for sharing, I'll be using this too.

AnimalRights

My brothers getting married today in a low key church wedding and there is no official photographer so I will bring my Cam and gear and see what happens, never been to a wedding b4 believe it or not let alone shot 1.
I think I'll go to the church early (starts at 4) and practice exposure etc

pixbyjohn

AnimalRights wrote: »

My brothers getting married today in a low key church wedding and there is no official photographer so I will bring my Cam and gear and see what happens, never been to a wedding b4 believe it or not let alone shot 1.
I think I'll go to the church early (starts at 4) and practice exposure etc

You will do yourself proud, just think of it as another gig

AnimalRights

:P
Best shots of gigs is when intoxicated....no such luck at the early stages of the church.