Why is this image not sharp?

[Retz]

This is a resized version of the photo. I'm specially concerned that there is not much detail in the flowers on the subjects head, even in this scaled down size. Camera settings were as follows: AF-S, single point (focused on her eye), Auto ISO "faster" shutter speed. Taken with the 85mm 1,4G lens.

 

[Halina123]

Shallow dof.

The only bit that looks sharp is the dress near the thighs where I can see the thread in focus.

 

[happysnapper64]

Thanks for your responses, here is the full sized image.

Looks back-focussed to me.

Was there a pause between when you focussed and when you took the picture - if so then maybe in that time she moved (her head) towards you, or you leaned towards her, or both, or the camera/lens simply mis-focussed.

Looking at the image reminded me of something -

I'm not familiar with your camera, but I'm wondering when you focussed on her eye (did you use a single auto focus point - without (the Nikon version) of automatic focus point expansion?

Reason I ask is that the Canon White Paper written a few years ago for the Canon 1Ds Mark II era cameras states that choosing via custom function to have the camera expand the AF points - this happens when the camera can't get a lock using the user selected single AF point -

"... can sometimes cause critical focus to shift slightly ahead of or behind relatively large 3-dimensional subjects like human beings..."

 

[Halina123]

If you want these type of images to be sharp and in focus try shooting f/4 instead of f/3.2 or f/2.5

 

[peterharvey]

Stop down the aperture for greater DOF, but most importantly, step back a little, because long distance increases DOF, however remember not to zoom in, but to shoot wider, because short FL increases DOF; crop your image if necessary.

Btw, is this your first FF camera?


Long subject distance.


Short FL.


Small aperture.

 

[Gerry Winterbourne]

This is a resized version of the photo. I'm specially concerned that there is not much detail in the flowers on the subjects head, even in this scaled down size. Camera settings were as follows: AF-S, single point (focused on her eye), Auto ISO "faster" shutter speed. Taken with the 85mm 1,4G lens.

I think there are several things to consider here (I'm replying here but I'm discussing your full resolution image).

First, parts of the image are sharp - you can see it on the apron below the lady's elbow next to the pens, where there is a lot of texture in the cloth. The elbow itself, though, together with other things nearer and further away, is quite soft. This points to your depth of field being too shallow, which isn't surprising at f/3.2 with that lens and the sort of distance you were shooting at. I'm sure you are familiar with DOF but try running your settings and shooting distance through any DOF calculator such as this http://www.dofmaster.com/dofjs.html

But there's an important point about DOF - it is the zone in which the image is considered acceptably sharp under a set of assumptions. But those assumptions actually suggest that resolution (which is a major component of sharpness) at the limits of DOF is often only about half of the resolution at the focus distance. In other words, even if the DOF calculates as being adequate you might still see softness.

Here's the Photozone test chart for your lens on a Nikon FX camera (not the same as yours so the resolution numbers might be different, although the shape of the chart will be the same). http://www.photozone.de/nikon_ff/606-nikkorafs8514ff?start=1 Note that it doesn't reach its peak resolution until f/4-5.6. So, quite apart from the shallowness of calculated DOF you aren't getting the sharpest possible image even at the focus distance. If end-of-DOF resolution is about half of focus-distance resolution than means it is down to something like 1800 at f/3.2 away from the centre, which is on the borderline between fair and poor.

It looks as though the lens wasn't focused ideally (that is, on her eyes) but it's not clear if that is because she moved after you'd focused or because of an AF error. Either way, however, you'd have had better results shooting at the lens's optimum aperture of about f.5.6. This would have given a (a) higher base resolution and (b) deeper DOF to disguise the slight mis-focus.

The background is far enough away that the deeper DOF wouldn't noticeably affect it.

Finally, there is some slight chromatic aberration visible. Although CA only shows up at high contrast edges it softens the whole image. Correcting the CA in post processing might give a marginal improvement in overall sharpness.

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[Retz]

Thanks again. I understand what you say about DOF and its dependence on distance to the subject but hey, this is a portrait lens. Actually yesterday I took a posed tight headshot with this lens at f2.2 and it looks sharper than either of the images I posted.

Maybe it is because it was taken at 1/800 instead of 1/400 or maybe because the subject was still.

@peterharvey Yes, my first FF.

@Halina123 What do you exactly mean by "this type of image".

 

[Halina123]

Thanks again. I understand what you say about DOF and its dependence on distance to the subject but hey, this is a portrait lens. Actually yesterday I took a posed tight headshot with this lens at f2.2 and it looks sharper than either of the images I posted.

Maybe it is because it was taken at 1/800 instead of 1/400 or maybe because the subject was still.

@peterharvey Yes, my first FF.

@Halina123 What do you exactly mean by "this type of image".

Both images look similar. A person with a lens of same focal length, taken at a similar distance. For the while person to be sharp and yet distinct from the background. You need to choose the aperture carefully. I think f2.5 & f3.2 give inadequate dof. F4 or f5.6 would give better results for this type of image.

It is possible to do a sharp headshot at F2.2. But difficult to photograph a whole person where the camera to subject distance has more variability.

 

[Gerry Winterbourne]

Thanks again. I understand what you say about DOF and its dependence on distance to the subject but hey, this is a portrait lens.

The fact that it's a "portrait" lens doesn't have much to do with it. There are two things about "portrait lenses" - one is that they have a focal length that allows a head shot, or head and shoulders, to fill the frame at a convenient shooting distance; the other is that some portrait lenses can be relatively soft.

That softness is intended to avoid showing unflattering details in, for example, skin blemishes. But if that was your concern here you wouldn't be asking about softness in the first place.

Actually yesterday I took a posed tight headshot with this lens at f2.2 and it looks sharper than either of the images I posted.

Mainly for the reason that that's what the lens is more suited for. A head shot doesn't have things like an arm sticking out in front of the DOF.

Maybe it is because it was taken at 1/800 instead of 1/400 or maybe because the subject was still.

I doubt it, except for the second-order result of movement - that the subject in the first shot you posted could have moved away from where you actually focused. The soft flowers in the lady's hair have nothing to do with shutter speed.

 

[Glen Barrington]

This is a resized version of the photo. I'm specially concerned that there is not much detail in the flowers on the subjects head, even in this scaled down size. Camera settings were as follows: AF-S, single point (focused on her eye), Auto ISO "faster" shutter speed. Taken with the 85mm 1,4G lens.

You say you focused on her eye, but when I view it with the DPR loupe, neither eye seems in focus to me.

Below is a link to an article from Robin Wong's blog where he demonstrates how to get the absolute BEST images possible from a very modest Olympus Kit lens. However, I think the principles he enumerates can probably apply to any camera and any lens. A lot of what he writes about in this article seems pretty universal.

Maximizing The Use of Kit Lens: Olympus M.Zuiko 14-42mm F3.5-5.6 EZ

Olympus, Micro Four Thirds, camera review, OM-D, photography, Malaysia photographer, photography tips, shutter therapy, street photography

robinwong.blogspot.com

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[Roonal_Z]

... Although I don't quite get what you say about single point AF.

I assume that since you are focusing on her eye that you thus have selected/chosen only one single auto-focus to be active - is this correct?

I'm looking through the D750 manual:

Which Autofocus Mode did you use - AF-A, AF-S, or AF-C?

Which Autofocus Area Mode did you use?

--
Good Day,
Roonal

 

[Retz]

This is a resized version of the photo. I'm specially concerned that there is not much detail in the flowers on the subjects head, even in this scaled down size. Camera settings were as follows: AF-S, single point (focused on her eye), Auto ISO "faster" shutter speed. Taken with the 85mm 1,4G lens.

You say you focused on her eye, but when I view it with the DPR loupe, neither eye seems in focus to me.

Below is a link to an article from Robin Wong's blog where he demonstrates how to get the absolute BEST images possible from a very modest Olympus Kit lens. However, I think the principles he enumerates can probably apply to any camera and any lens. A lot of what he writes about in this article seems pretty universal.

https://robinwong.blogspot.com/2016/05/maximizing-use-of-kit-lens-olympus.html

--

That's exactly what my question is about. OK, will read the article.

 

[Retz]

Does the D750 lock the focus when you hold the shutter button half pressed? I may have kept it helf pressed for a little while and the subject moved forward a little.

 

[Glen Barrington]

I don't know, I am an Olympus guy. Maybe some Nikon guys will pop in and answer.

 

[Antioch]

This is a resized version of the photo. I'm specially concerned that there is not much detail in the flowers on the subjects head, even in this scaled down size. Camera settings were as follows: AF-S, single point (focused on her eye), Auto ISO "faster" shutter speed. Taken with the 85mm 1,4G lens.

Focus is in front of the image. Probably did not realise you were doing it, or the camera/lens need to be calibrated.

 

[JoeyRoa]

Thank you for the DOF master link.

 

[Roonal_Z]

Does the D750 lock the focus when you hold the shutter button half pressed? I may have kept it helf pressed for a little while and the subject moved forward a little.

P. 121 of the user manual

http://download.nikonimglib.com/archive2/zTWQD00yGQnW012RcxZ15FTj6882/D750FM_DL(En)01.pdf

Applies if using shutter button to focus, not using back-button focus (AE-L/AF-L button) - p. 361-362.

As well as (??? don't have a D750 to check) not using AE-L/AF-L button to "lock focus"???

--
Good Day,
Roonal

 

[Retz]

It says "Focus locks when shutter release button is pressed half way". I'm positive this is the problem. A street photographer shouldn't be hesitant!