What happened to the focus (Page 3): I have the 80-400 and did the focus target on it and when I put the 1.7TC on it. I did it again. I had to go up+2 for the combination.

Erv Loc: Medina Ohio

I have the 80-400 and did the focus target on it and when I put the 1.7TC on it. I did it again. I had to go up+2 for the combination.

oldtigger wrote:

brings up a question, if a zoom needs to be focus calibrated at the zoom range it will be used, does a zoom plus extender also need to be calibrated?
Or do we just assume adding the extender changes nothing?

JoeJoe

oldtigger wrote:

i don't think much of anything is correct in that sentence.

Ok ....try focussing on a white piece of paper..Apart from hunting for some contrast you will wait forever for autofocus to find it..then put a line on the paper and do the same exercise..... DoF works by having 1/3rd in front 2/3rds behind (basic photography).... oldtigger you may think its wrong but I know its correct..... the difference between the two of us... one understands the other doesn't.... I'll let everyone else decide...

oldtigger Loc: Roanoke Virginia-USA

JoeJoe wrote:

...Focus uses a contrasting edge to gauge distance then converts that to your lens to create 1/3rd DoF in front of object / subject.

the camera uses data describing phase or contrast to generate a drive signal to the lens focus motor.
The lens moves until the data represents a value which the system considers 'ok', at which time the lens is assumed focused and drive ceases.
The camera is aware of the magnitude of the focus error to control response rate in some cases but has no interest in DOF.

JoeJoe

oldtigger wrote:

the camera uses data describing phase or contrast to generate a drive signal to the lens focus motor.
The lens moves until the data represents a value which the system considers 'ok', at which time the lens is assumed focused and drive ceases.
The camera is aware of the magnitude of the focus error to control response rate in some cases but has no interest in DOF.

So why have fine tune for auto focus in the Nikon Menu if the camera knows and corrects?? if your statement is correct...looks like the engineers at Nikon have made a big mistake on the focus system menus in adding a useless function and you are correcting them..or you have in your description and understanding
it uses distance to subject in its calculation along with aperture (which we all know controls DoF) and lens along with finding contrast to calculate.... a sure fire test is put your camera on a tripod lay a tape measure on the floor and set your aperture as low as you can..F1.4 in my case... then focus on a defined point to check DoF (Focus) ....then fine tune your lens to the findings ......quite simple and thank god Nikon engineers got it right in adding the adjustment in the menu..... then again I might be wrong

oldtigger Loc: Roanoke Virginia-USA

JoeJoe wrote:

So why have fine tune for auto focus in the Nikon ... (show quote)

i understand your point.
The camera does not have to know the distance, it only needs the phase/contrast error. Define an error value greater and of a different value as null drive and the lens assumes a different position. Add the actual distance determined by the lens position and you can add lookup tables which trick the camera into offsetting itself different amounts for different distances.
Those engineers are pretty slick but i if the camera actually determined focus point in terms of DOF/hyperfocal distance the add boys would have told us about it long ago.

JoeJoe

oldtigger wrote:

i understand your point. br The camera does not ha... (show quote)

Its called Fine tune....... they told everyone about it years ago after the D5100 Back focussing debacle... A focus point is a mechanical action unlike WB averaging...... we could go on for hours debating this but in real life the answer is simple.. test your kit against known calibration methods and adjust using software menus that make sense of your findings...and let the camera do the work without trying to blow the minds of beginners and keen amateurs with techno babble from the instruction manual that means nothing in the real world.

Test your kit on a tripod
use a tape measure as you will see definite movement of the DoF
adjust your camera
test again 5 times to ensure stability
once you've done it a few times it becomes instinct and takes seconds to do in the field.

Had a D5100 and learnt a lot on focussing.. check Back focussing Nikon on Utube d5100 and you will realise the sensor can move in time and will have major effects on your focussing that without micro adjustments will give out of focus shots every time.

JoeJoe

oldtigger wrote:

i understand your point. br The camera does not ha... (show quote)

Just read your sharpness/detail post....Lol

Why have you put distance into the post if the camera doesn't need to kow....
This is a prime example of a shot that is using an uncalibrated lens that is clearly back focussing, your DoF starts at the tip of the sign the man is holding.... greatest contrasting point on the 51 af system at that distance which should have told your camera to adjust F6.3 which is clearly at 25 metres a wider DOF to cover the man and sign 1/3rd in front of that point...instead your camera lens combo chose to focus behind..... camera error or operator error...... operator error not calibrating the lens to body

Meives Loc: FORT LAUDERDALE

Howard, The rule that I was taught is that the shutter speed should be equal or greater than the mm of the lens used. Shutter = 1/mm You were at 1/400 and the lens was 1000. This could cause total blur. David I re-read your post and you used a tripod.

foathog Loc: Greensboro, NC

take a look at the focus point. The branches in front of the bird are IN focus, whereas, the bird and the branches close to the bird are not. you would need a LOT of DOF to capture the bird with that focus

Howard5252 Loc: New York / Florida (now)

foathog wrote:

take a look at the focus point.

The focus point was on the bird's head- both times. This is why I asked my initial question?

boberic Loc: Quiet Corner, Connecticut. Ex long Islander

Apaflo wrote:

There is no such thing as averaging focus.

your'e right- I meant to say metering and use spot focus

speters Loc: Grangeville/Idaho

Howard5252 wrote:

Both photos taken using Nikon equipment and a trip... (show quote)

Why does it bother you that the focus distance is the same, if you did not change your position, the focus distance will always be the same?

JCam Loc: MD Eastern Shore

Apaflo wrote:

There is no focus averaging.

The OP is talking about a Nikon camera. Nikon cameras can have many "focus points", but only one of them is selected to measure the focus. There is no averaging, ever.

But the one the camera selects, may not be the best one for the photo, ie. the bird or the larger branch.

Howard5252 Loc: New York / Florida (now)

speters wrote:

Why does it bother you that the focus distance is the same, if you did not change your position, the focus distance will always be the same?

What bothered me was the fact that the focus appears to have changed, even though I focused on the same part of the bird. I know the DOF changed but it seems to me that the bird should have been within all of DOF's.

Howard5252 Loc: New York / Florida (now)

JCam wrote:

But the one the camera selects, may not be the best one for the photo, ie. the bird or the larger branch.

As I mentioned before the focus point in the viewfinder was on the head of the bird for both shots.