NikonGear'23
Gear Talk => Lens Talk => Topic started by: atpaula on April 17, 2016, 14:12:43
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I thought telephotos were easier to focus.
I've never missed so many images with a lens.
But I'm loving the ones I nail focus.
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I meant "telephotos were HARDER to focus".
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This lens is very fast and getting properly focused images should therefore be very easy. At least that is my experience with fast wide angles on my Nikons.
Thus, I'm curious as to what camera was used and any reasons you feel could cause this behaviour. Have you tried focusing on pin light sources - they ought to be easy to get spot on.
I assume you have set the eye piece ocular correct according to your eyesight.
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tele can be easier because you actually see things go in and out of focus. 50mm and below and be trickier in my experience :o :o :o
now, following something is more difficult with tele than a normal say 50mm ::)
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This lens is very fast and getting properly focused images should therefore be very easy. At least that is my experience with fast wide angles on my Nikons.
Thus, I'm curious as to what camera was used and any reasons you feel could cause this behaviour. Have you tried focusing on pin light sources - they ought to be easy to get spot on.
I assume you have set the eye piece ocular correct according to your eyesight.
The problem is that you think you have proper focus during the shooting, but them the computer tells you were wrong.
Nikon's DK-17M eyepiece didn't help much. Maybe for static subjects, and the camera on a tripod it could help.
It is very tricky.
Richard's experience corroborate that.
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You should have your camera checked for misalignment.
My 20/1.8, 24/1.8, 24/1.4 & 35/1.4 are all very easy to focus manually.
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You should have your camera checked for misalignment.
My 20/1.8, 24/1.8, 24/1.4 & 35/1.4 are all very easy to focus manually.
The problem is the photographer, not the camera or lens. Mostly at f/1.4.
Closer than infinity it is very tricky to distinguish in/out of focus through the OVF.
If I stop down the lens the problem (characteristic?) is mitigated.
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Aguinaldo , I really enjoy the colors you get
Regarding focus with a fast wide angle, I have run into similar situations with my 20mm f1.8 AFS, I tried focus-recompose and then discover the image is not in focus ... It was surprising for me to find out the 20mm lens wouldn't have enough DOF to cover any movement I may have done when recomposing, since missing a few images due to bad focus, I'm now more careful
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Aguinaldo , I really enjoy the colors you get
Regarding focus with a fast wide angle, I have run into similar situations with my 20mm f1.8 AFS, I tried focus-recompose and then discover the image is not in focus ... It was surprising for me to find out the 20mm lens wouldn't have enough DOF to cover any movement I may have done when recomposing, since missing a few images due to bad focus, I'm now more careful
Thank you Armando.
With the 20mm @ f/1.8 the problem may be even worse.
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Try finding some street lights and use them as training targets for manual focusing.
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Stock focus screen? I'm sure you are aware that shooting any lens at aperatures faster than f/2.8 with the stock screen is a gamble. The faster you get the larger the margin for error.
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Using both the D3 and the D800, I found my copy of the Zeiss 25/2 to be slightly more difficult to eye focus than most lenses. My experience with the Zeiss 100/2 was similar.
Part of it could be the "f/2.8 optical restriction" of the modern finders, but then why do other, similarly spec'd lenses prove easier to focus?
My untested hypothesis is that with most lenses, a constellation of aberrations make the slightly out of focus image appear "more out of focus" in the finder than with lenses like the ZF 25/2 or ZF 100/2 that have a higher degree of correction.
From all reports, the Otus 28 would fit into the category of lenses that are unusually highly corrected wide open.
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Stock focus screen? I'm sure you are aware that shooting any lens at aperatures faster than f/2.8 with the stock screen is a gamble. The faster you get the larger the margin for error.
Is it possible to change the focusing screen of the D4s? I didn't know that.
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Using both the D3 and the D800, I found my copy of the Zeiss 25/2 to be slightly more difficult to eye focus than most lenses. My experience with the Zeiss 100/2 was similar.
Part of it could be the "f/2.8 optical restriction" of the modern finders, but then why do other, similarly spec'd lenses prove easier to focus?
My untested hypothesis is that with most lenses, a constellation of aberrations make the slightly out of focus image appear "more out of focus" in the finder than with lenses like the ZF 25/2 or ZF 100/2 that have a higher degree of correction.
From all reports, the Otus 28 would fit into the category of lenses that are unusually highly corrected wide open.
I think the focusing confirmation green light should work precisely, regardless of lens aperture.
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I think the focusing confirmation green light should work precisely, regardless of lens aperture.
It usually does, but there is plenty of room for user error. Much depends on what is in front of, or behind, the point of focus, and how large that point is.
Contrary to what humans believe, cameras have no idea about what constitutes 'sharpness' in an image. The camera can only maximise a given function, which may or may not be relevant.
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I think the focusing confirmation green light should work precisely, regardless of lens aperture.
If the camera is well calibrated. You can also fine-tune the AF sensors for manual lenses. It has occurred to me once or twice that I needed to do this.
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Is it possible to change the focusing screen of the D4s? I didn't know that.
Focusingscreen.com carries screens for the D4s, so yes. Looks like the D4s selection isn't great right now, but I'm sure if you contacted them you could get what you want. I use the S type, which is just a Canon S screen. I wouldn't use it for anything slower than f/4, or even f/2.8 in dim conditions, but it is excellent for fast lenses. Many here, including Bjørn R, use the K3 and enjoy it. I would like to try one but can't comment.
As for the green dot, it can help a lot sometimes . If I have a static subject/time I can focus at any aperature by eye, which I find better for composure. So not needed. If I have a moving and unpredictable subject, it is of no use as I need to keep my eye on the composition. It's the in between situations where I find it useful. Certainly not a tool to be relied on though, which is why I would not go without a screen optimized for speed unless I had no lenses faster than f/2.8.
What would be grand, is if Nikon put out a firmware update that lit up focal points when they are in focus (while manually focusing) and/or adopted an option for the pentax style hold-shutter-down-while-focusing release. If future higher end Nikons had the focus direction arrows for each AF point that could be enabled, allowing for use of the "green dot" without taking your eyes off the composition . . . that would be fantastic. But that is all wish-listing of course. ::)
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and/or adopted an option for the pentax style hold-shutter-down-while-focusing release.
Setting AF-S or AF-C to focus priority on your Nikon does does allow this function a pity it seems to only apply to AF lenses, though it works when manually focusing AF lenses also. I wonder why they disabled it for manual focus. Any firmware hackers out there? ;)
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Someone correct me if I'm wrong but I believe the green dot focus confirmation display has anit-flicker built in which limits its accuracy. I find it useless as a manual focus aid. As I see it the only thing it does is tells you the camera "thinks" it's in focus. It might be affected by the AF fine tune default value if set. If a camera is out of calibration the green dot can't be in calibration. It's a phase detection driven display.
I found manual focus on the matte focus screen with my D2H quite reasonable but my D300s and D800 less so.
Dave
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so far, the blinking dot serves me well :o :o :o
well enough for me to remove the focusing screen that I DIY'd on my D7200...
the problem i see is that on some bodies, the focusing for the meter and viewfinder doesnt match and this has to be calibrated in the mirrorbox. it is not difficult but tedious ::)
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Someone correct me if I'm wrong but I believe the green dot focus confirmation display has anit-flicker built in which limits its accuracy. I find it useless as a manual focus aid. As I see it the only thing it does is tells you the camera "thinks" it's in focus. It might be affected by the AF fine tune default value if set. If a camera is out of calibration the green dot can't be in calibration. It's a phase detection driven display.
I agree with everything but the 'only'. This is no different than AF, the camera might think it is in focus but the proof of the pudding is in whether the image on the sensor is in focus, so the optical path length from mirror to AF sensor and mirror to sensor have to match.
I have the feeling that the AF system has improved considerably over the last couple of years, also improving the reliability of the green dot for manual focus. But it is still the case that one has to practice its use: for fast lenses, there is a considerable interval of focus distances which lead to a dot appearing, the margins of which are marked by a dot-arrow rapid flickering pattern. You have to know for each aperture at which point in that interval the best focus lies. It may be in the middle, but it may also be somewhere close to the edge. The reason for this variability might be the different degrees of correction of spherical aberrations of the lens. With a fast lens, the edges of the 'dot appearing' interval might lead to a badly defocused picture, so it is not enough to simply wait for the dot and shoot.
After some practice, one can use the green dot without looking at it. Peripheral vision is enough to decide the points at which it flickers, and one can focus on composition and what's happening with the subject.
I don't question the ability of some people to focus their lenses through the viewfinder (with the stock screens and without looking at the green dot), and I understand that the Df might be especially well suited to this task, but I don't think it is a viable solution for everyone to achieve a near 100% hit rate with fast lenses. When the light levels are low (dusk and dawn, where f/1.2 is maybe the only aperture that still allows one to shoot at normal ISO levels), my eyes cannot see what is sharp anymore, but the dot usually still works (recent AF sensors have insane sensitivities).
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by the way, blinking green dot to me is close enough ::)
this is what i do when i calibrate manual focus lenses. if i can make the dot solid with just tweaking tolerances then better, or else i will need to file stuff here and there (helicoid stop). :o :o :o
by the way, some lenses actually focus a little bit past infinity. i read somewhere that this is to compensate for the elements expanding under high heat. i believe this was from a canon related site. i need to mention this just in case.
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Some very sharp lenses have a very narrow band of 'depth of sharpness' it is very revealing of focus errors.
Most lenses have a very smooth transition in and out of 'depth of field' masking focus errors.
The green dot is 'for info' only for such a sharp lens on a modern AF camera with standard screen - more or less,,,
For 100% reliable images; Get a Zacuto finder Pro, and use live view, works in sunshine and even pitch black darkness. Did anyone say mirrorless ::)
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speaking of mirrorless (somebody opened the pandora's box ::) )
i really hope that Nikon would implement focus peaking even in it's simplest form. :o :o :o
that would be awesome for people like me who focus stack bugs from time to time as i have poor eyesight.
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Erik, is it worth starting up a new thread on the Zacuto finder Pro?
I know little about the device, but it would be good to hear from those that have used it.
(I do realise that the OVF zealots might lynch you for starting up such a thread and they might also lynch me for suggesting the thread and reading the postings! ;D ;D ;D ;D)
Link: http://www.zacuto.com/z-finder-dslr-viewfinder
Some very sharp lenses have a very narrow band of 'depth of sharpness' it is very revealing of focus errors.
Most lenses have a very smooth transition in and out of 'depth of field' masking focus errors.
The green dot is 'for info' only for such a sharp lens on a modern AF camera with standard screen - more or less,,,
For 100% reliable images; Get a Zacuto finder Pro, and use live view, works in sunshine and even pitch black darkness. Did anyone say mirrorless ::)
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We're broad-minded here, not 'zealots'. And 'lynching' belongs to another time in history - or so I hope.
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i am an OVF "purist" for photography ::)
but for video, EVF is the way to go. Zacuto finders are expensive but they are irreplaceable for us when filming using a digicam, mirrorless or otherwise :o :o :o the cheaper alternatives like Hoodman are also nice ::)
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Ha ha, well,,, Fun aside, the Zacuto is an optical viewfinder that fits on any camera display so just another practical tool in the box.
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The Hoodman loupe, a less-expensive competitor to the Zacuto, is optically excellent but physically/mechanically feeble. The optional metal bracketry, however, is very thin and is easily bent. The Hoodman bracket cannot be seriously recommended for professional field use for that reason.
It may accommodate a greater range in it's diopter adjustment than the Zacuto...that was my experience when inspecting existing rigs.