You want to tell me, when shooting with a 70-200 in AF-C @ 20fps at f/8, the aperture blades would open up to f/5.6, focus, then close to f/8 20 times per second?
800mm f6.3S PF Review - Thom Hogan
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It would be the same aperture for focus if your shooting wide open would it not since it can not go below the maximum aperture of the lens can it?i think not due to a quirk in how mirrorless af works. it autofocuses with one aperture, then takes the shot with another. but seriously, i doubt this is a significant real world issue since if i’m shooting at f16 or something my dof is increased.
this smells like one of those theoretical issues that people say to remind you they know about them
John Navitsky
Well-known member
i’m guessing Steve’s book probably covers it. i guess we’ll see if i both remember and have time to look for it. perhaps it only changes it if it’s wider than 5.6. otoh, Joel’s question is still relevant, if it changes it to af, does it do it every frame?
Joel,
my guess is that it only returns to 5.6 once you release the shutter button.
If you are at f/5.6 or wider, the camera uses the aperture of the camera. If you are at f/6.3 or higher, the cameras uses f/5.6 or the wide open aperture of the lens or len+TC combination.
So in your example, if you are using a 70-200 f/2.8 at f/8, the camera is using f/5.6 for focus. And yes, it would adjust focus for every frame even at 20 fps. I assume that means it is adjusting aperture as well. Said another way, the resting position between frames is f/5.6 so you have adequate light to focus.
With DSLRs that's exactly what they did except the blades open all the way to max aperture. I've not yet seen a definitive explanation as to whether MILC do that or whether the blades simply stay open. I believe with Z bodies they pinch down to 5.6. I have seen it stated definitively by Nikon(in some interview with Nikon engineer) that the Z9 meters/focuses at selected aperture up to 5.6. So presumably simply locks the blades there while shooting. At higher apertures?
Maljo
Well-known member
No. The camera focuses wide open, then stops down to take the image at the selected aperture. It's stopping down the lens after it has focused. Changing the aperture may change where the light focuses, no longer perfectly on the sensor plane. Its not a problem shooting wide open and does not look like much of a problem from the images at Camera Labs.
It does and I read it before I left but it mentions going to f/5.6 in the part I read but nothing related to lenses that do not open that wide like the 800. That was in the Secrets to the Nilkon Autofocus System Mirrorless edition. @EricBowles said it is f/5.6 or the widest aperture of the lens. So for the Z800 it would be f/6.3 which is where I am the vast majority of the time.
I found where I missed it on page 366.
"Speaking of lens apertures, let’s talk about lenses that have a wider (faster) maximum opening than F/5.6 because the Z cameras do a neat little trick.
If you have your F/stop set faster (wider) than F/5.6, the lens will focus and operate at your selected F/stop. However, if you set to an F/stop of F/5.6 or slower (smaller), the camera will drop to F/5.6 for focus."
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Which answers my other question.
When shooting @f/1.2 through f/5.6, The aperture is staying put. = ZERO focus shift.
Its only when shooting at above f/5.6 or in the case of the 800pf it’s f/6.3, its only going to jump back and forth between shots back to wide open if the exposure is stopped down.
Which brings me to another question.
I understood that the focus shift phenomenon is this only is super fast lenses using very big aperture openings. Even @ f/2.8 the issue gets minimized, and @ f/5.6 it should be almost nonexistent, because the opening of the aperture blades are smaller.
So, here comes my question; Who cares if the 800pf is shooting @ f/6.3 because its the best the optics can do, or because its an imaginary 800mm f/1.2 stopped down to f/6.3. At those smaller aperture openings, the issues should not even exist! not because we have more depth of field which covers it, but rather because of the opening of a smaller aperture, focus shift doesn’t happen inside.
Got my question?
Another question,
If it’s true that the camera would try to keep the aperture is wide-open as possible, How can we have any focus shift in the 24-70/4 lens?
If it’s true that the camera would try to keep the aperture is wide-open as possible, How can we have any focus shift in the 24-70/4 lens?
If there was anything that was actually material to see it would be going from anything above f/5.6 in that lens back to f/5.6. So if you were at f/8, f//11, f/16 etc. it would focus at f/5.6 hence the depth of field preview button for the landscape shooters out there. Last landscape I did was from on top of a high ridge looking accross a whole bunch or other ridges at the Sawtooth Mountains probably 50 air miles away. I took it with the Z800 since I had it in my hand and it did a great job of showing the layers (compressed of course) and the almost blue hour colors.
John Navitsky
Well-known member
i think the heart of Joel's question is if the aperture mechanism if fast enough to flip back and forth when shooting 20fps (or faster).
i recall the A1 has some noted limitations about changing exposure in high speed burst modes which might also relate to how fast the aperture mechanism is? there is also the thing where not all lenses can shoot in the high speed modes, which, assuming their af works in a similar manner, perhaps is related?
In the DSLR days true impactful focus shift and back and front focus issues were magnified to us birders by our typical long focal lengths of 600 mm (the most prevalent) I used 150-600 f/6.3 on the long end, 60-600 f/6.3 at the long end and 600 f.4. Very few used the 800mm f/5.6 since it was very expensive and a logistics headache. We typically shot wide open and the depth of field was very shallow on even small subject the closer to the minimum focal length you got.
I shot the 600 f/4 and a 500pf with and without a 1.4TC on my Z9 but not the others and those were shot wide open almost all of the time and on the Z 9 I never noticed any issues of back or front focus as I had with a couple of DSLR's that I had to focus tune or in one case send the body and lens to Tamron and the calibrated the lens to the body. As a Tamron rep, widely known for his technical expertise, told me they had never had to do that with a Sony mirrorless and did not anticipate doing it with Nikon when they got the ok to make non adapted lenses for the Zmount.
As soon as I got a Z100-400 and Z1.4 TC I sold the 500pf and as Steve did his pre release video review on the Z800 I sold my 600 f/4E and ordered the Z800 an my order was in before the release so had an order number and my NPS priority delivery request in seconds after it was available to do so at a smaller brick and mortar store in CA and I was the first order there let alone the only NPS order on the first day. So that is why I have had a Z800 since 5-1-22 and have a lot of experience with it.
I shot the 600 f/4 and a 500pf with and without a 1.4TC on my Z9 but not the others and those were shot wide open almost all of the time and on the Z 9 I never noticed any issues of back or front focus as I had with a couple of DSLR's that I had to focus tune or in one case send the body and lens to Tamron and the calibrated the lens to the body. As a Tamron rep, widely known for his technical expertise, told me they had never had to do that with a Sony mirrorless and did not anticipate doing it with Nikon when they got the ok to make non adapted lenses for the Zmount.
As soon as I got a Z100-400 and Z1.4 TC I sold the 500pf and as Steve did his pre release video review on the Z800 I sold my 600 f/4E and ordered the Z800 an my order was in before the release so had an order number and my NPS priority delivery request in seconds after it was available to do so at a smaller brick and mortar store in CA and I was the first order there let alone the only NPS order on the first day. So that is why I have had a Z800 since 5-1-22 and have a lot of experience with it.
Yep, it’s one of my questions nailed.
I don’t believe that the lens blades could move so much so fast and so precise.
Imagine the Z9 with a 50mm prime shooting at f/8 @ 120fps… that calculates to 240 different precise positions in one second…. Nah… hard to believe
LOL ... I could imagine it but would have no need for it
John Navitsky
Well-known member
there could be nuance to the answer. my understanding is that the need to flip aperture for autofocus is to aid subject detection. it's possible it only needs to do this for the initial af operation, and then the focus is close enough that it doesn't need an assist.
could be .... it is not function I see happen with the Z800 but if I know I have a backlighted bird or one in shade with bright light around it I am increasing ev or dropping shutter speed or both as I start bringing the viewfinder to my eye since proper exposure is extremely helpful with AF and subject detection.
Anyone ever here the old saying about telling time without knowing how the clock works?
My point I want to outline is, I don’t believe, and nor is there evidence that
the blades are resetting before each exposure in AF-C. So a bracket while stopped down wouldn’t / or shouldn’t have focus shift in frame 2 and on.
the blades are resetting before each exposure in AF-C. So a bracket while stopped down wouldn’t / or shouldn’t have focus shift in frame 2 and on.
Actually it’s possible to video record the blades in slow mo. Just need 2 cameras
John Navitsky
Well-known member
or a cell phone
I have a 800 PF lens and with my limited use, find it very nice to shoot. Stationary birds in a nest are very easy to capture. Birds in flight are currently a challenge for me. I have taken several shots but not happy with my results. I will be practicing with a tripod and gimbal and using a monopod. I am trying to select the appropriate focus points and AF for moving subjects. Also, I have to upgrade my Z to 3.01.
Just my experience so far.
Just my experience so far.
In the case of the Z9, Nikon has stated it adjusts focus for every frame at 20 fps. In that scenario, it should also be adjusting aperture since that is how it focuses. Nikon has been using an electronic aperture for for about 20 years, so it would not surprise me if the camera/lenses are adjusting aperture. They were doing that with the F-mount as well - focusing wide open and then stopping down to the aperture selected for every frame in a burst.
This was historically the limitation on AF during a burst. But it was changed with some of the more recent cameras. Exposure changes during a burst were also limited, but that is not the case today on the top cameras. There are a number of processes taking place in a high speed burst. Each camera's engineers decided where compromises were needed. For example, some cameras drop frames so the EVF can show a high speed burst, some reduce the resolution, and some keep it native.
I have been using the Z9 with Z800 since 5-1-22. I am a bird photographer. I photograph them in all sizes, weather, terrain and habitat here in Idaho. I am always on the move following and searching for birds and hand hold all of the time.
The latest firmware is now 3.10 for the Z9.
You do not say what settings you are using for BIF? I get great results with the Z9 and Z800.
@Steve had great books and The ultimate Nikon Z9 Setup and Shooting Guide for Wildlife Photography is a great one to start with.
And just in case you find it useful these are the basic settings I use.
I shoot manual with auto ISO and AF-C. I have a7 focus point persistence on auto to help facilitate hand off from one AF Area mode to another. I have animal subject detection on.
I have my buttons for AF-Area Mode and AF set to:
Shutter half press wide-area AF C1 sized to 5x3.
AF/ON button to AFArea mode 3D + AF-ON
Fn1 button to AFArea mode single point + AF-ON
Fn2 button to AFArea mode to AF Area Mode + AF-ON
For birds in flight if from my experience the bird, background, distance etc. I select which AF-area mode I will start with and change as needed while I am shooting.
Many times I will use shutter release button focus wide area AF C1 5x3 only.
Other times I start with C1 5x3 and when in focus hand off to 3D or AF Area mode both work quite well but I use 3D for more precision and auto area for situations of erratic flight or multiple birds where I want to change from one bird to the another.
I seldom use single point AF on BIF but will if I want precision and animal detection off.
After FW 3.01 and now with FW 3.1 I now frequently go directly to 3D or AF Area mode directly by pushing the button I have set.
For focus help I make sure I have good exposure and even start to adjust as I bring the camera to my eye if I now I will need to move my ev up (I have my lens control ring set to adjust EV) or change shutter speed.
I also have a button on the lens programmed to toggle between FX and DX and find that can help with AF.
I also have my video record button programmed to toggle subject detection on and off.
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