Only 90%!? For me it's closer to 98% I reckon
It's been documented that Nikon's 153 point AF system does sometimes focus on the background rather than the subject in certain scenarios. I first saw it mentioned on the D5 (was it @sk66 that mentioned it?)) and I too had it happen to me on the D850. It looks like it's happened here too. My experience was when there was a busy background and the subject was small in the frame.
spot (single) cell focus?
I have had this happen on both Nikon and canon - I put it down to my poor technique.
Less of an issue with that, but I think I had the odd one that did it with single point.
TBH it can happen with most cameras, I think it's more prone with the Nikon 153 point system for some reason. I wish I could find that thread as I can't remember why. I know the OP was in conversation with Nikon for quite a while about it, but I can't remember what the outcome was.
The outcome from Nikon was "it's as designed."
With the 153pt AF system in a dynamic mode it releases tracking much sooner and it doesn't function in a "nearest" manner anymore. The "blocked shot delay" is really just a "refocus delay," and it will happily select stuff farther away when it times out. The only slight exception is group mode which does *kind of* perform with a "nearest priority."
Also worth noting is that both the 51pt and 153pt systems are *not* using only the selected point to acquire focus when in a dynamic mode (maybe any mode, I haven't actually tested). It is also using all of the focus points immediately around the selected point... if the selected point fails to find a good focus it will lock on using the surrounding points if it can.
The PDAF system of a DSLR is using the position (phase) of very tiny images to determine focus... it cannot see/resolve very small details in the scene (it functions very much like a split screen viewfinder does).
You are expecting too much, and there are some user error/understanding issues as well I think.
By default, if you are using back button focus Nikons do not really care if the subject is in focus when using a dynamic mode, regardless of the release priority setting (it only cares for the very first initial acquisition).
The distance is too great. As others noted the atmospheric conditions will affect things... it can be heat, moisture, dust, etc, but there is always some crap in the air. Nothing makes as much of a difference as getting closer does, it helps reduce the atmospheric issue, and it makes the details larger so the PDAF system can actually see/resolve them.
Distance also affects SS requirements. If the subject is in motion then you need a higher SS when it is closer. But you also need a much higher SS when the subject is more distant regardless of it's speed. As an example, put your finger over something fairly large and relatively close; something like a chair across the room. Now move your finger around... how far does it have to move before it's not over the chair any more? Now put your finger over something about the same size about 100ft away... how far does it have to move now? That's exactly the same thing that occurs when trying to keep "pixel on detail" to prevent recording motion blur. And that image movement is also affecting the tiny images the PDAF sensor is trying to use.
So I was right, it was you that posted about the problem Thanks for posting again, sorry I couldn't find the original thread. Interesting that the dynamic mode doesn't necessarily select the chosen focus point when acquiring and tracking focus, that's useful info. I thought that the AF lock on wasn't as sticky in my D850 as it was on my D750 but thought it must've just been my imagination so thanks for clarifying that it's not just me So I guess the only mode that's close to guaranteeing it's going to AF on your subject and not the background or whatever is single point? TBH that's what I've find with any camera I've used. I've tried 3D, group, dynamic, (plus the different Sony modes such as flexible spot when I had that) and always revert back to single point as I find it the most accurate and consistent. Fortunately for me I rarely shoot BIF so don't need group etc
Am I right in thinking that you said that the AF system is more likely to focus on the background when it's a busy background?
Thanks @sk66, your explanation makes complete sense, and confirms what others have said on the thread but also adds the importance of a high shutter speed a greater distances, 1/800 may not have been enough given the amount of movement at my end - I don't think my monopod was appropriate equipment for the job at hand. I normally carry it instead of my tripod for convenience, but I'm realising that me not being steady enough is the likely cause of the soft images, rather than an focus issue. The softness does look a bit more like motion blur too.
I have been only using dynamic points for BIF, and on this occasion I was using single point.
I'm keen to try again with my tripod - a higher shutter speed. Perhaps a remote shutter too? Would you recommend tightening off the gimbal head prior to taking the shot when the subject is static?
Also, my experience with VR is that when I have it on - when I activate the shutter, I notice that the view through the viewfinder 'jumps' and when it returns to normal, the focus spot may have 'jumped' from the intended initial placing before activating the shutter. At first I thought that might have been the cause of missed focus.For that reason I have had it switched off, only switching it on when light is poor, and I have to drop my shutter speed below 1/focal lengh. Should I be using VR in circumstances like this when I have my shutter speed up above 1/800. Do you use VR when shooting BF at 1/1250 and above using dynamic AF?
Credit to @kingo15 and @HoppyUK too. They did mention shutter speed earlier too
Back home soon, will send over the RAWs, and some samples with my other lens where AF didn't work out for me at the wedding. With the way things are going, it does look like the failure is down to user error rather than faulty equipment!! Blush.
P.S. I'm a guy
User error is cheaper than gear problems
sorry about that - I did not know if you were "Gil" or "Bev" - sometimes difficult on these forums - maybe I should use OP.
you can get sharpe images at a distance - but unfortunately some think that once you spend £5k on a 500mm or 600mm and stick it on the end of a £2k camera all your"bird image" problems are solved - it is the reverse and the longer lenses are far more difficult to use ....... on good quiet days when I have plenty of time I use a Nikon 600mm on a really good heavy weight Gitzo tripod and a WibberlyWobberly Gimbal - but I have tried many other combinations.
I find the most practical solution to shooting birds when walking around in the field to be the Nikon 300PF with a x 1.4TC - using if possible a lightweight Gitzo Mountaineer Tripod with just a regular Gitzo lightweight ballhead (I never use monopods - tried them, don't work for me and if I want a "monopod" I just use the Gitzo and pull in the legs) - For Birds, I also prefer the D750 to the D810 or any DX Nikon, (I'm not a fan of the D500 - just me - apparently it's a good camera) ......... in the hide I would take the 300mm f2.8VR with the x 2 TC plus the 750 with the PF and x 1.4TC (with the x 1.7TC in my bag) and use both hand held or resting on the bean bag/hide shelf - you need to be comfortable when shooting and have the flexibility to move.
I always use spot single cell focus and my default would be + 1/3EV - using manual mode so that I can adjust both Av and SS at the same time, auto ISO within ranges, but you can push ISO depending on shooting conditions and your PP ability
What I think many people do not realise is that (if you do not practice your technique) the camera (and therefore the focus point) will move when you press the trigger, it's always been like that, but even more so with a SLR - just try it - using the focus point plug in software - focus on a bird - press the trigger then look at your images - when you took the shot you were convinced that you had hit the birds eye - then look at the results in LR - you will be surprised how many times you missed the birds eye, (birds move even when they are still!!!) - but the user moves as does the camera when you press the shutter.
You can try, LV, Mu and remote - but by the time you have set that up the bird has probably gone!!
Remember, as well, that the focus point in the viewfinder is an approximation. It will vary from camera to camera (but shouldn't be out too much).
Here are the original RAWs for the images posted above as well as a few extras. I haven't yet tried to download and install the AF software suggested. @BillN_33, maybe you could take a look if you have time
I need access - can you just PM me the file - just add it to a PM
Give it a go now, I don't think the settings were correct initially to allow everybody access.
Quite right - I notice this on many occasions. Looks like I've got a bit more practise to do with long distance shots.
LV - live view, Mu - not sure what Mu is?
Can you just send me them in a PM - just attach them to a PM - 2 or 3 files will do
Mu - Mirror up - to stop the movement when you press the shutter
Here you go @Gil Bev - your focus point info :
1. No focus point information - possibly no BBF action
2. Focus point on the bird but not locked
3. Focus achieved and locked but subject is small in the frame (My solution is simply to get closer through fieldcraft).
4. Focus not locked again.
5. Focus achieved and locked but on the bg behind the Heron.
IMO, all of these shots are too far away, especially given the atmospheric conditions and shooting over water, to give ideal satisfactory results.
You say that your rig isn't very stable, so you would need very good long lens technique and I would be inclined to raise the SS to a minimum of 1/2000
I haven't read all the thread but this is my two penneth' worth
Whilst we have people posting poor advice, some people will never learn.
Taking shots that need to be cropped this heavy will never be anything other than record shots.
Long lens photography is about trying to fill the frame with the subject, at least fill it to a point where its acceptable to crop a decent sharp shot.
No disrespect Gil, but your first post says it all
You may have heard this but I've seen absolutely no evidence of any shots being posted that are sharp at 100% crop, never mind 200%/300%
And just to prove this point. Here's a shot with the D850 and then a 1:1 crop. Whilst not too bad, it's not stellar either. Usable though imo.
DSC_7711-Edit by TDG-77, on Flickr
DSC_7711-Edit-2 by TDG-77, on Flickr
Looking at the the images sent one of the main problems is (too low) shutter speed and movement, (by the subject and probably camera movement)
all shots are at low ISO's and most at 1/800th sec
as Wez says use much higher shutters speeds and push the ISO higher to get shots that have less "blur"
Practice long lens technique and then lower shutters speeds will be possible
all shots seem to have been taken at the same distance, but strangely enough the image with no focus point info is the only one that is half decent - apparently Gil use manual focus for this image!
I'm not looking to achieve outstanding results at this distance, however my aim was to be able to record behaviour to an acceptable degree (image quality wise) without disturbing the subjects. As you can see I was failing miserably - my images were all blurred / out of focus, but with the advice I've had, I'm happy I have some valid points and suggestions which have improved my understanding and no doubt improve the results I will be able to achieve.
I find that the pictures that have the most impact, are pictures that record an unusual behaviour - and on many occasions you just can't get close enough - particularly when there is no cover without interrupting that behaviour you want to record. I'd like to be able to have the skill to take good pictures both distant, albeit not as detailed as well as the more pleasing photos when you do get the opportunity to get close enough, or be close enough. I also find myself in the position of being far away from the subject more often than close-by so it would be good to be able to take acceptable photos rather than none at all, at least come home with something interesting, rather than nothing at all.
For example, I would have been really happy if this one had come out at a more acceptable sharpness, I think it's quite comical
HSC_5947_full by Gilbo B, on Flickr
Yes, this was the one I concentrated hard and kept the mono-pod as still as I possibly could in order to use manual focus. I was determined to get something that was reasonable, and I was trying everything I could without really having an understanding of what was going wrong.
Which is where bag hides come into play. Lay down on the shore and be patient. Or, I'd try to find somewhere with more cover that enables you to get closer to a subject. You can turn up hoping to go away with something that you like but, more often than not, you'll go home disappointed. If I took 500 shots, I'd probably end up deleting 490 of them and only showing my best one or two. Bear that in mind
TBH I'd have thought 1/800 would be more than enough even if used on a crop body, assuming VR was active of course. I can hand hold my 150-600mm at 600mm at 1/160 quite comfortably with VC enabled.
I would agree - but Gil is just starting to use a long lens and it is important to try to get sharpe shots, at any distance, and then gradually work back from there
Gil - don't be discouraged from taking long shots, provided it's not a Robin at 200 mtrs - I've got lots of shots at 100mtrs, 200mtrs, (Cranes, Large Vultures), which I think are quite effective - just produce the best image technically that you can under the circumstances
It's not to hard to find problems ,just take shots of say a cereal box with clear print / graphic's at 20mt 40mt and 60mt at around 1/2000 this will tell you if you can indeed take a sharp shot, early morning then later to see if heat haze is part of the problem .
You need to be confident in you gear before anything else comes into play .
There are six possible axises, movements, when taking a photograph.
Five are combo related — that amplify their effect the greater the dis-
tance to the subject — and one that is not. So the sensible decision is
to reduce or eliminate the movements and their effects on sharpness.
Taking the collar foot of the lens as the centre of the combo, these five
vertical — up and down
perpendicular — sideways
frontal — fore/backwards
pan or swing
All of them will work together against your aim and VR can rarely cope
simultaneously with all of these properly. My old 600mm ƒ4 is a pre-VR
version — and other lenses that I have were never used with VR!
The only great advantage of shooting handheld is the immediate capa-
bility to react faster to any situation but that comes to a cost as well.
Using a monopod will solve ONLY the vertical axis problem, not more.
A tripod with decent gimbal will solve three problem sources: 1, 2, & 3.
One needs 4 and 5 to actually take the shots and using the appropriate
amount of head damping in these two movements will surely help.
The last movement in the equation is the subject. Not only its movement
in space but, in case of say birds, the wings flapping. I these two cases,
proper panning skills and SS, respectively, are the solutions.
ONE MORE POINT
When shooting handheld, one must consider a SS that will cope with the
subject and the five movements, with the consequence of higher ISO and
/or shallower DoF… not really a solution for me.
The right decisions in a well thought out strategy will increase the overall
sharpness and surely the number of keepers in a session.
VR should be activated early enough that it stabilizes before taking the image. A stabilized image also helps the PDAF module...
This would suggest to me that you're not half pressing the shutter first to acquire focus before taking the shot. At half press (or full press if you don't get focus first) the image can sometimes 'jump' when VR kicks in, however after this is should be stable. Whether shooting AF-S or AF-C I would always recommend half pressing the shutter first to acquire focus (and activate the VR) and then fully pressing the shutter (without releasing if first from the half press position). This should give you much better focus accuracy/hit rate, and will also avoid any issues when VR activates.
This is not what I recommend my students that did setup
BBF and deactivated focusing through half pressed SR
as its only function is to wake up and start the metering.
And for those that don't like BBF?
Legitimate question, Toby!
Everyone has a favourite approach to the AF situation. Mine is
that I should be able to do anything, everything, any/every time
so I can increase the keepers. A ratio 10:500 as mentioned be-
fore is not a viable solution for one (me) to make an income of it.
Cameras come with fantastic integrated features that allow one
to perform the way it is required. In my book, not liking or refusing
to adopt an available technology that would make possible many
pictures that were not before, is as understandable as not lacing
one shoes before going out… my sons went though that!
I'm always in favour of embracing new tech and ideas, but I am yet to prefer BBF no matter how much opportunity I give it But either way, my point was that (imo) it is better to lock/activate AF whether by means of BBF or half press shutter prior to taking the shot to allow time for the AF to acquire a better lock on, and also give time for the VR to become active and stable.
Absolutely, that's why there is a menu that fixes that by allowing
triggering ONLY upon focus acquisition. You are using Nikon like
me so should have no problem with this.
I never use VR… almost taboo in my book.
Some Nikons if you use BBF it overrides the focus acquisition before shutter release setting, dont know about the later ones though.
That would also make sense as the AF is constantly on
as long as the BBF is pressed, Mike and that makes it
ideal for high continuous mode.
If it's set to AF-C focus should be constantly 'changing' whether using BBF or half shutter press, or do you mean the shutter release on focus setting?