Lens aberration?

[chuck]

Using the 24-70 AFS with the D810, I notice a problem when shooting at night at a lite object like a neon sign. When I use full

magnification on the live view to focus, the sign appears sharp on the monitor. But when I actually take the picture, the image of the sign

appears slightly blurry at the same magnification, and is surrounded by a halo the same color as the sign.

 

I thought it might be chromatic aberration, but that should split the color of the sign and scatter its component colors around the edges,

not create a halo the same color as the light. Also, if there were chromatic aberration, why does it not appear on the live view?

[Ray House]

<p>How about attaching the photo?</p>

[ilkka_nissila]

<p>Did you evaluate the image on a computer monitor or using the camera's LCD? If the latter, and if you're shooting NEF, the camera displays a basic quality JPG with potentially lots of artifacts.</p>

<p>It could also be internal flare in the lens.</p>

[Ed_Ingold]

<p>Light from bright, overexposed objects will spill over into darker areas in the image. This could be due to scattering in the sensor, but more likely due to flare in the lens. The higher the ISO, the smaller the dynamic range of the sensor, hence the greater the tendency to overexpose highlights along with flare.</p>

<p>Camera motion will also cause details to spread when viewed at the pixel level. With an high resolution camera like a D810, you will find it very difficult to eliminate camera motion at any shutter speed, much less hand-held at night. Even using a tripod, I find it necessary to use the electronic first curtain shutter, and a flexible cable release (or self-timer). It goes without saying the mirror would have to be pre-released.</p>

[Robin Smith]

<p>I suggest it is due to effective overexposure of the neon in the resulting shot, this will cause the surrounding dark areas to be lightened and produce a halation effect, as Edward says. In live view the camera usually adjusts the screen automatically to bright lights so it may well look better then during magnified focusing. You can avoid it my exposing "correctly" for the highlights, but if you do that you will lose shadow detail. You need some kind of exposure compromise for it to look how you want it.</p>

[Ed_Ingold]

<p>I have seen some interesting studies which indicate you retain more detail in high-contrast areas (e.g., neon lights and other lighted signs at night) if you underexpose, then raise the shadows in post. Modern CMOS sensors have low noise and do particularly well using this technique.</p>

[User_4754088]

<p>I've been caught out by what Ilkka talks about above. Looking at a NEF file on the camera LCD after taking a picture, looks low quality. Same image on my desktop looks beautiful.</p>

[Andrew Garrard]

<p>Just checking you're sure about "at the same magnification" - Nikons do let you zoom past 100%, which has caused some confusion in the past. Otherwise, the only reasons I'd expect to see a difference between live view and the final shot are with a focus shift on stop-down (if you're using live view wide open), sharpening settings, or if the shutter is causing vibration. Oh, actually, or what Edward says about the ISO effectively being different. And I've no idea how well lens corrections are applied during live view, if at all. A crop of the final image and some details of your settings might help us track it down?</p>

[ShunCheung]

<p>Hi Chuck, as Ray points out, could you please post a sample image or two to illustrate this issue?</p>

[chuck]

<p>Sorry, I was away on a business trip, which was then extended to include a personal weekend in California and Yosemite. </p>

<p>I suspect I know what is happening. I suspect the LV is substantially underexposing the low light image it shows. As a result, the image looks noisy, but aberrations like flares are too dim to see. When the shutter is actually tripped, the camera correctly exposes the image. This makes flare and other aberrations much plainer.</p>

<p>At Yosemite, I attempted to photograph the night sky from Glacier point and the valley floor, it is clear LV is essentially worthless in such circumstances because exposure value is so low that almost nothing, including the artificial lights on the valley floor, is visible. But a 6 second exposure actually produce ghosting and flares around artificial lighting.</p>

<p> </p>