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Camera: Nikon D5600 Lens: 70-300 mm
I am using this lens for bird photography. From the last few months, I noticed even when the bird is not moving and I try to focus using the Manual Mode with Single Point focus, I find later when I zoom the photo on my laptop, the bird is slightly blurred.
In the settings I found "Long Exposure" set to ON, which I think was OFF by default.
I want to know whether Long Exposure set to ON is interfering with the camera focus.
No, the Long Exposure NR setting is not causing any blurriness or interfering with the camera focus.
Long Exposure Noise Reduction only kicks in if the exposure is longer than 1 second, and really is only useful when taking long exposures in dark situations (such as night sky photography). Basically, it's an in-camera dark frame subtraction technique. When capturing long exposures in low light, thermal and pattern noise become very noticeable. One technique to help reduce noise is to take a so-called dark frame, which is basically just shooting with the lens cap on, for the same duration (and ideally, at the same temperature) as the photo of interest.
The Long Exposure NR setting does exactly that: when you take a long exposure with the setting on, as soon as the exposure duration is done, the camera takes another exposure with the shutter closed, thus taking a dark frame. At the end of the dark frame exposure, the camera subtracts the dark frame pixel values from the original long exposure pixel values, resulting an image with reduced thermal and pattern noise.
But this doesn't come in to play with your bird photography, unless your photos are longer than 1 seconds. And if that's the case, you should eliminate camera vibration and motion from possible causes of blur. =)
It depends on the blur type. Usually:
Motion blur happens if the camera moves during the exposure. When shooting hand held with a 300mm on an APS-C camera, you should shoot at something faster than 1/500s(*). If the lens features image stabilization you can go down to about 1/100 and still have clear shots. You can also use a tripod or a monopod.
Focus blur happens if the focus is not correct:
Zooms have a rather shallow depth of field. Having the lens wide open requires a very accurate focus, things can be mitigated by closing a bit (using the lens around f/8, for instance)
Assuming good focus and rock-solid tripod, this can come from a lens that is a bit soft because it is used at its extremes (focal length and aperture). Try to de-zoom a bit and close a bit.
Using faster speeds and smaller apertures may require to increase ISO, resulting in more noise. Photography is often a matter of choosing your lesser evil...
Then, pixel-peeping one's pictures is always disappointing :)
(*) This comes from the "1/f" rule. When hand-held, a full-frame camera without stabilization, you should use a speed faster that the reciprocal of the focal lengh, for instance 1/250s if your lens is a 200mm. On an APS-C cameras you have to take in account the crop factor and multiply the result by 1.5-1.6 (this usually the "next" speed, so 1/400s). But this rule if for overall sharpness, if you pixel-peep you need even faster exposures.
I doubt that Long Exposure NR plays in. First of all it is not used unless you are using very long exposure times, which is not really useful when shooting birds. Second, it would not result in blurry images, as it works by evening out the amount of light captured by each pixel-cell on the senor, as their difference in sensiblity becomes more visible as the exposure time increases.
I think it is much more likely that you are underestimating the shutter speed that is required when using longer lenses. As a rule of thumb, it is desired to have at least 1.5 - 2 times the focal length used for long lenses. The longer the lens, the more vulnerable it is to even the tiniest amount of movement during the exposure. So, if you are taking a picture of a bird at 300mm, you should aim at shutter speeds of at least 1/500s if the bird is stationary and even more if it is moving. Image stabilization will counter this to some degree. It can counter some of the movement/shake caused by the photographer, but it will not counter tiny movements of the bird (especially its feathers).
