D1 - Dynamic Low Light - Why no one knew?

Recently I posted a few observations on this forum about the AF back focusing and the dynamic low light performance.

I am surprised the no one actually filled me in on the tech aspects of either of these – no one knew about the back-focus issue (here).

But more importantly no one knew about the low light poor performance of the AF system if it is in Dynamic AF.

I am surprised that Thom Hogan did not alert me to the fact that the system must be used in bright light and cannot be used in low light situations. This is “apparently” the official word – if it is the manual I missed it. I will not re-read the D1x manual to find out one way or the other –. The warning about low light AF-Dynamic is “apparently” in the D1 manual.

Hello Gerald

We usually respond to things we have experience with, Personally I try for good lighting and never shoot in low light conditions if I don't have too, consequently no experience with that low light and dynamic AF focusing situation... I am sure the others are the same.

Stephen

Ger Bee said:

Recently I posted a few observations on this forum about the AF
back focusing and the dynamic low light performance.

I am surprised the no one actually filled me in on the tech aspects
of either of these – no one knew about the back-focus issue (here).

But more importantly no one knew about the low light poor
performance of the AF system if it is in Dynamic AF.

I am surprised that Thom Hogan did not alert me to the fact that
the system must be used in bright light and cannot be used in low

light situations. This is “apparently” the official word – if it is
the manual I missed it. I will not re-read the D1x manual to find
out one way or the other –. The warning about low light AF-Dynamic
is “apparently” in the D1 manual.

Click to expand...

-- http://www.livick.com

Stephen Livick said:

We usually respond to things we have experience with,

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And your info is pretty good usually.

Stephen Livick said:

I am sure the others are the same.

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Hmm, do the photo journalists avoid this forum ?

I do available light indoors shooting mostly, and find the AF on the D1X workable, but far from perfect. In about 1 shot out of 10, I need to hunt until I can get a focus at all due to the amount of light, with the 17-35. I may be wrong on this but I have the impression that sometimes the camera just sits there and refuses to fire because it cannot aquire focus. This is not a complaint, I like the camera, but I would love a faster "standard" zoom and/or an improved autofocus.

Stephen Livick said:

Stephen

Ger Bee said:

Recently I posted a few observations on this forum about the AF
back focusing and the dynamic low light performance.

I am surprised the no one actually filled me in on the tech aspects
of either of these – no one knew about the back-focus issue (here).

Click to expand...

Click to expand...

--Look Ma, no film !

Stephen Livick said:

Hello Gerald

We usually respond to things we have experience with, Personally I
try for good lighting and never shoot in low light conditions if I
don't have too, consequently no experience with that low light and
dynamic AF focusing situation... I am sure the others are the
same.

Stephen

Click to expand...

Yes Stephen, I'm sure you are right.

I drew a little flak on this subject when I was trying to trace a focusing issue. In brief I noticed that my sequence shots were progressively out of focus - it turns out that this is a known problem (not my me!!!) and had “plagued the D1 – the back focussing issue!”

In my attempts to thwart this (until the new year when the D1x will go to Nikon) I tried the closest focus (Dynamic AF) – this seems to work but another problem emerges – camera lockup for a few seconds (resultant pictures are perfect from a focus point of view – it just takes several seconds before the shutter fires) – now it turns out that this is not recommended in low light – officially and may even be in the manual!!! I failed to pick up on this, did you notice a warning not to use dynamic AF in low light or to use in bright light only - anywhere in the manual?

Ger

I knew about this so it must be in the manual for either the D1X or SB28DX??

Ger Bee said:

Recently I posted a few observations on this forum about the AF
back focusing and the dynamic low light performance.

I am surprised the no one actually filled me in on the tech aspects
of either of these – no one knew about the back-focus issue (here).

But more importantly no one knew about the low light poor
performance of the AF system if it is in Dynamic AF.

I am surprised that Thom Hogan did not alert me to the fact that
the system must be used in bright light and cannot be used in low

light situations. This is “apparently” the official word – if it is
the manual I missed it. I will not re-read the D1x manual to find
out one way or the other –. The warning about low light AF-Dynamic
is “apparently” in the D1 manual.

Click to expand...

I may be wrong on this but I have the

Edmund Ronald said:

impression that sometimes the camera just sits there and refuses to
fire because it cannot aquire focus.

Click to expand...

I seem to find this too – I am often re-aiming the camera to get it to “wake up” and re-focus. But try keeping the shutter pressed for several seconds - it may fire then - I'm calling this the camera "lockup" syndrome.

The D1x has two distinct focussing systems – one is better than the other. C-AF is the best in low light acquisition but can wander – as it is designed to do.

Add dynamic into the mix and the problem becomes acute – there were a lot of posts advising that dynamic be turned off but no one explored the reasons (just like the E10 when people were being advised to switch off the E10’s greatest asset, IR focus– in the dark focus).

If I put up with the delay - the system does work - since I've proved its existence I’ve been telling people to wait it will fire in a minute it is just calculating the distance in the dark as it actually cannot see – and then it fires – not suitable for working in – but I still find it the best – most accurate – focusing.

Roger Woolman said:

I knew about this so it must be in the manual for either the D1X or
SB28DX??

Click to expand...

If it in the D1x manual I missed it. I did not read the SB28Dx's manual at all.

Ger, everyone,

In available light, no flash, which mode do you recommend - C or S or dynamic ? I can afford to wait a second or so, mostly, but need exact focus exactly where I put it.

Sorry if I seem dumb, but I use the D1X as an outstanding point and shoot.

Edmund--Look Ma, no film !

I'm finding that S-AF dynamic (closest focus) is working the best as far as accuracy is concerned - but in low light it definitely has this "lock-up" or apparent non- responsiveness.

My nicest – crispest pictures are from this setting – presumably because the subject lies inside the zone of focus rather than at the back edge – it also give the D1x a fantastic P&S value with no worries about off centre or the gap between people – a real beauty and one I did not explore until recently.

Edmund Ronald said:

Ger, everyone,

In available light, no flash, which mode do you recommend - C or S
or dynamic ? I can afford to wait a second or so, mostly, but need
exact focus exactly where I put it.

Sorry if I seem dumb, but I use the D1X as an outstanding point
and shoot.

Edmund
--
Look Ma, no film !

Click to expand...

My problem, I usually want just ONE focus zone in perfect focus, the rest unsharp - on purpose. How do I achieve this best in low ight ?

E.

Ger Bee said:

I am surprised the no one actually filled me in on the tech aspects
of either of these – no one knew about the back-focus issue (here).

But more importantly no one knew about the low light poor
performance of the AF system if it is in Dynamic AF.

I am surprised that Thom Hogan did not alert me to the fact that
the system must be used in bright light and cannot be used in low
light situations. This is “apparently” the official word – if it is
the manual I missed it. I will not re-read the D1x manual to find
out one way or the other –. The warning about low light AF-Dynamic
is “apparently” in the D1 manual.

Click to expand...

The D1 manual says "Autofocus performs best when...the subject is well lit..." and a lot of other generalities.

The Nikon autofocus system uses a passive, contrast-based system (as do most film and digital SLRs). There a lots of nuances to the system, including the fact that the focusing system works best on horizontal motion (e.g., hold the camera vertically and you'll get somewhat different results than if you hold it horizontally). I've documented as much as I know about the autofocus system (which is a lot) in my books.

"Must be used in bright light." Not true, but there must be contrast in the object under the sensor. An all-black t-shirt that fell on the sensor would usually not have enough contrast to hold focus. If you don't have contrast in the subject, you'll need to turn the autofocus assist lamp on, though I'd be the first one to admit that Nikon made a mistake here--Minolta's patterned autofocus assist lamp does a far better job of providing useful contrast info to the camera than Nikon's unpatterned light.

Finally, while I try to answer posts here about specific issues, I also travel a lot, and generally don't answer questions that get posted during those time periods (at least not at length, since I'm often connected via cellphone in the middle of no-where) unless the discussion is lively enough to extend past my travel.

As for "official word," I've found Nikon USA to be mostly unhelpful in resolving technical issues, and I suspect that Nikon UK is the same. A few good stores in the US know more about Nikon's equipment than do most of the folks at Nikon USA (there are a couple of exceptions, but those people do their best not to stay hidden and not answer direct inquiries). Not a way to run a company, IMHO.--Thom Hoganauthor, Nikon Field Guideauthor, Nikon Flash Guideauthor, Complete Guide to the Nikon D1, D1h, & D1xwww.bythom.com

Thom Hogan said:

--
Thom Hogan
author, Nikon Field Guide
author, Nikon Flash Guide
author, Complete Guide to the Nikon D1, D1h, & D1x
http://www.bythom.com

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I have my credit card statement and I'll look for that activation thingy for PayPal - so I'll be reading one of your books in the new-year.

The bright light bit is right though - specifically with Dynamic activation.

One zone of focus is best with C-AF - it is also the most sensitive in low light.

Edmund Ronald said:

My problem, I usually want just ONE focus zone in perfect focus,
the rest unsharp - on purpose. How do I achieve this best in low
ight ?

E.

Click to expand...

Ger Bee said:

The D1x has two distinct focussing systems – one is better than the
other. C-AF is the best in low light acquisition but can wander –
as it is designed to do.

Click to expand...

It's not two distinct focusing systems, actually. It's the same system used two different ways. In dynamic focus you're telling the camera that the subject may be moving and to continue to evaluate all five sensors (yes, it evaluates all five, even if you've only picked one). If you get non-contrasty information under one of those sensors, the camera will wait until it gets usable information before "finishing" its autofocus operation.

But there's another aspect of the focus sensors that you need to know: they are not all created alike, nor are they aligned alike. There's an illustration in the book, but the short story is that the left, central, and right sensors (holding the camera normally) are "cross" sensors and can detect focus better (read: faster) than the top and bottom sensor, which are "line" sensors. The left, top, and right sensors are also angled slightly, which can also lead to some unusual occurances in autofocus (if you were taking a photograph of a series of tightly space horizontal lines, the bottom sensor would be useless [and hold up dynamic autofocus], the top and central sensors would be okay, and the left and right sensors would respond the fastest and easiest.

If all this suggests that I sometimes put my D1x into single area autofocus mode in low light, you bet I do. I also tend to cancel Closest Subject Priority, as well, as it, too seems to affect low light performance.

But all passive autofocus systems generally have reachable low light limits with non-contrasty subjects. I've been known to put my flash on my camera, switch to single servo autofocus and point the flash head straight up (remember, I shoot outdoors mostly). This gives me a quasi-active autofocus system, as the flash emits enough red autofocus assist light to improve focus certainty.--Thom Hoganauthor, Nikon Field Guideauthor, Nikon Flash Guideauthor, Complete Guide to the Nikon D1, D1h, & D1xwww.bythom.com

Edmund Ronald said:

In available light, no flash, which mode do you recommend - C or S
or dynamic ? I can afford to wait a second or so, mostly, but need
exact focus exactly where I put it.

Click to expand...

If you want focus exactly where you put it, then single area autofocus (or use the focus lock button).

If you can tolerate waits, use closest focus priority, continuous autofocus, dynamic autofocus mode (I wish Nikon wouldn't be so liberal and redundant in making up buzzterms for things--it sure makes it hard to describe all the features without confusing anyone).

Of course, I tend to use manual focus most of the time, so what would I know ; )--Thom Hoganauthor, Nikon Field Guideauthor, Nikon Flash Guideauthor, Complete Guide to the Nikon D1, D1h, & D1xwww.bythom.com

I have own my D1H for only a month or two, but I do shoot a lot in low light situations with no flash. This requires me to use ISO 800-1600 to get a decent shutter speed. Shooting equestrian sports in arenas lite mostly by mercury vapor, which with shutter speeds in excess of 1/120 is a entire subject in itself, I have experimented with both C-AF and C-AF Dynamic. I have received good results with both. I would agree that C-AF is a little more consistent than C-AF Dynamic and I would shoot with C-AF only if the subject would just stay in one focus area! So in my particular case C-AF Dynamic provides an advantage that I cannot ignore.

I have really enjoyed this thread! In particular, the difference in subject focal plane placement depending on the type of focusing used.

The very best,
David

Ger Bee said:

Ger Bee said:

--
Thom Hogan
author, Nikon Field Guide
author, Nikon Flash Guide
author, Complete Guide to the Nikon D1, D1h, & D1x
http://www.bythom.com

Click to expand...

I have my credit card statement and I'll look for that activation
thingy for PayPal - so I'll be reading one of your books in the
new-year.

The bright light bit is right though - specifically with Dynamic
activation.

Click to expand...

--David Richardson

Ger Bee wrote:
? if it is

Ger Bee said:

the manual I missed it. I will not re-read the D1x manual to find
out one way or the other ?. The warning about low light AF-Dynamic
is ?apparently? in the D1 manual.
Page 583, paragraph 12 (Chinese Version)

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