Just consider, I could as well have basic problems with AF. To be honest, I don't know what the decisive factor in autofocusing is. AF-C helps me a lot because I'm moving as well when focusing at close distances. Should I look for lines or structures? So far my guess was "lines". Vertical? Horizontal? Diagonal? How often are there some lines? No real clue, the manual doesn't explain much about that important stuff, it remains very vague. As I saw in the light chain pictures, there are patterns a CDAF can handle better.
What I don't like is that surprise box and find afterwards "not bad, but I've seen better from this lens".
You don't need to look specifically for "lines". Just any kind of contrast will do, even if they are tiny specs of pollen on a for the rest featureless background.
It can happen that one misfousses when there is a repeating pattern, where PD AF may think one contrast edge is another, and then says things are in focus. But that happens very seldom, and mostly only with line type AF points.
It can also happen that there are edges of contrast, but only in the vertical orientation where the AF point used has a vertical line sensor point. Then it can happen the AF does not see any edge. This too is very seldom.
PD AF misfocus happens in two circumstances: Apparently, it is said that Nikon cameras with Sigma lenses (probably also with other lenses) can somehow misfocus in artificial light, because the light "bends" differently and the AF conclusions are not valid as they are with white light and the AF with the lens does not get corrected for that. Not sure if that is a correct explanation, or if something else occurs, but I have read a number of times of someone complaining that with artificial light OOF results are produced.
And then there is the problem when the lens is not calibrated correctly "for the camera body", and steps and especially final steps in the AF process are different than what one expects, resulting in an OOF result. Often the results then are different when starting the Af from infinity than when starting from MFD.
Also, aberrations can influence what the AF sensor sees, being different from what the image sensor gets.
With CD AF, you can get OOF results from lenses/cameras overstepping exact focus and not realizing that, since they can't actually see when something is in focus, and only have a difference in contrast to go on. And at darker circumstances the live view image stream can get too noisy to do contrast comparisons from frame to frame.
Happy Christmas Guys!!!!!!! and may all your points of focus be sharp and all your OOFs be smooth and creamy!
I once did an experiment with a ball hanging from the ceiling by a thin chord (Pentax), when the AF point was on the ball, the AF was spot on, when the AF point was half on half off, it was BF, the less on the ball the more BF'd it was. I now never use edges, just surfaces!
The same on eyes, I try not to include the eyebrow.
I read a post which makes the light source issue cause more plausible. It might be that with certain artificial light sources, where the AF with at least certain Nikons gets inaccurate, IR plays a role. Might it be that the AF sensor focusses on the IR light, which then causes OOF results? The poster was thinking about an IR cut filter, to test this.
Quote:The story is quite simple: Although I adjusted AF for the Sigma 20/1.4 in front of a D810, the LiveView based contrast detection AF knows better in most cases or equally good and never (!) worse. There are about 3 shots where both kinds of AF came to the same conclusion. I didn't show all the samples. But I've seen enough.
It was highly unscientific - without any tripod and probably some blur came for shutter/mirror vibration. I count that as one reason more to abandon mirrors... all shots were done in about ½ hour, just by walking through the streets, take one picture with AF-C, move the AF-point to a suitable place and focus. Then I switched to LV, focused again and released. There's a note in the gallery which tells just what I said. The bicycle was trickier and here I enlarged the AF zone in LV and adjusted manually. The little jewelry tree was also tricky, I didn't see the branch in foreground in the viewfinder, but thought, I was focusing at the face plaquet under the rear branch. That was were I put the AF to in LV, again with manual adjustment. The wall painting with the soldier in a small creek, the light chains on the facia - hopeless to get that with PDAF.
In the gallery is only the first picture with PDAF. Plus a comparison of the AF zone at 100% crop. My conclusion: It's close to pointless in terms of getting the full resolution, the most possible information out of a picture if I (you or others may do better) can't rely on PDAF, adjusted as good as it gets with FoCal. Fast lenses = pricey lenses and in my case high resolving sensor, outresolved by the lens in theory. In real life crashed and smashed by a second best AF device. When I was adjusting the lenses, the spread of focus quality is visible in any FoCal protocol although the software triggers AF and shutter. If I go to check various focus points, I even see which one are weak.
As you said, dave, LV is a pain in terms of speed and of no use in street photography with a DSLR and I fully agree. Of course, DSLRs are not made for street photography with LV. Checking proper focus afterwards? Yes, why not. Unless I don't compare it with the potential of the LV versions, I was always fine with the results and thought, that's as good as it gets. True, for PDAF it is. But there's more in the lenses and I can't see it in most samples.
If you can accept the lower resolution, I recommend the Sony A7s with dedicated sony lenses for accurate low light AF. The A7s + 55mm 1.8 Zony make a very satisfying combination. Alternatively the A7rii probably has lower AF sensitivity (and less sensitive EVF) due to partial sensor read out in live view but will enable PDAF with DSLR lenses. However the A7s can probably be had for about $1500 used versus $3000+ for the a7rii. Since I got my A7s I am convinced to totally transition away from DSLR cameras as for my style of shooting (portraiture, street, low light) DSLRs are simply obsolete technology ( in the sense that there is a better solution now available).
Quote:I read a post which makes the light source issue cause more plausible. It might be that with certain artificial light sources, where the AF with at least certain Nikons gets inaccurate, IR plays a role. Might it be that the AF sensor focusses on the IR light, which then causes OOF results? The poster was thinking about an IR cut filter, to test this.
This was also a problem with the Pentax K5, they put a IR in the K5II which cured it. I will be seriously keeping an eye on this low light business as I will with all matters of AF.
Quote:If you can accept the lower resolution, I recommend the Sony A7s with dedicated sony lenses for accurate low light AF. The A7s + 55mm 1.8 Zony make a very satisfying combination. Alternatively the A7rii probably has lower AF sensitivity (and less sensitive EVF) due to partial sensor read out in live view but will enable PDAF with DSLR lenses. However the A7s can probably be had for about $1500 used versus $3000+ for the a7rii. Since I got my A7s I am convinced to totally transition away from DSLR cameras as for my style of shooting (portraiture, street, low light) DSLRs are simply obsolete technology ( in the sense that there is a better solution now available).
More than once I was playing with this idea, Ayoh. I just think, I'll wait for one or two iterations and meanwhile borrow an A7RII to make my own practical view. I read too much about quirky interface, but I know, the longer I wait, the less money I get for my DSLR gear.
There's a bit uncertainty about the differences of A7II, A7SII and A7RII - except the "high ISO" and "high resolution" as main feature I really don't get the point, how the additional character in the name is worth double the price of a A7II.
Poor battery performance, knowledge of a 4 million dots resolving EVF (in a Leica) make me hesitate. Also, I don't think, Nikon will not answer sooner or later the Sony threat although it's probably a different mount on a Nikon FF mirrorless.
Meanwhile I'll make my first mirrorless system steps with a little Fuji and two lenses as I always wanted to have something much lighter than DSLR but at comparable Quality level.
Quote:More than once I was playing with this idea, Ayoh. I just think, I'll wait for one or two iterations and meanwhile borrow an A7RII to make my own practical view. I read too much about quirky interface, but I know, the longer I wait, the less money I get for my DSLR gear.
There's a bit uncertainty about the differences of A7II, A7SII and A7RII - except the "high ISO" and "high resolution" as main feature I really don't get the point, how the additional character in the name is worth double the price of a A7II.
Poor battery performance, knowledge of a 4 million dots resolving EVF (in a Leica) make me hesitate. Also, I don't think, Nikon will not answer sooner or later the Sony threat although it's probably a different mount on a Nikon FF mirrorless.
Meanwhile I'll make my first mirrorless system steps with a little Fuji and two lenses as I always wanted to have something much lighter than DSLR but at comparable Quality level.
Wow taking the first steps!
I was sneaking around those Fujis for quite a while. The position of "lightweight, but decent travel camera" ion my bag is unoccupied, since I was no longer happy with Canon G11's IQ (which is not that bad) and for traveling those FF bodies with some primes are sometimes overkill. After reading the manual of the Fuji and watching thxbb12's results I'm looking forward to it's delivery. So I guess, a couple of brand-new Fuji models is about to appear very soon and all better than the "old" ones ^_^
With a current Fuji or are you waiting for a new Fuji model? I take it you will still hang in there with the D750/ D810?
The Camera Store gave the Leica second worst camera of the year, man it's so big and heavy and "expensive " you can live without one kidney but for the Leica you would have to sell both.... :ph34r: 
If you want to raise some money for the "Sports" 
|
