Hello,
I have an R7 and I'm extremely happy with how it handles in good light, however, when trying to photograph an owl last week at dusk, the image came out terribly noisy and unusable.
Image quality in any scenario is largely determined by the total light used to make a photo. Whether at dusk or midmorning on a sunny day, the f-stop and shutter speed used will determine how much available light gets delivered to the sensor. That's going to determine overall image quality.
I was using R7 and 200-800mm. I can't remember the exif completely but the iso was at maximum or there abouts.
I know APS-C sensors aren't built for low light photography and LLP is more suited to FF cameras.
My question is, and I apologise if this is a stupid question, I'm new to photography.
Does "better low light capabilities" mean that a higher iso can be used? If so, am I going to run into similar problems using FF and a higher iso? Will the image still be noisy or does the larger sensor reduce the noise? Resulting in a cleaner image?
ISO is the setting we use to manage image lightness: will the photo look light or dark. It doesn't directly attract how much light is used to make a photo ans it's not a source of noise.
I'd disagree with this to the extent that as you increase the ISO the amount of light you capture to achieve a correctly exposed image of a scene will reduce, and the ISO implementation will (effectively) brighten the scene more to compensate.
You're crediting correlation as being causation. It's not.
Shutter speed and f-stop are the only camera settings that directly affect how much light from the scene is delivered to the sensor. The total light energy used to make a photo determines shot noise. ISO is nowhere to be found in that equation.
Read noise is determined by internal data processing. ISO reports the relationship between exposure and a target image lightness to the camera. That's ISO's role. The camera uses this information to process a JPEG with a given lightness.
Prior to the development of dual gain sensors, the read noise in a photo processed at a low ISO was much worse than the read noise in a photo processed at a high ISO. If two photos were made with the same exposure but one at ISO 400 and the other at ISO 3200, increasing the lightness of the ISO 400 image in Photoshop would reveal the debilitating read noise in that photo. The image made at ISO 3200 would have the same lightness and shot noise, but much lower read noise.
Today with dual-gain sensors being fairly common, a photographer can use a lower ISO to protect important highlights and lighten the shadows in post without concern that read noise will be an issue.
If you're shooting at light level Ev 12 (a heavily overcast day) then correct exposures for a "normal" subject (no white snow or coal heaps) will be:
f/5.6, ISO 100 -> 1/125th
f/5.6, ISO 400 -> 1/500th
So you capture 1/4 the light in the second example, and so get twice the Photon Shot Noise.
ISO, of course, does not determine the weather, f-stop or shutter speed. However, the available light, virtual entrance pupil diameter and exposure time do determine exposure. Exposure and the surface area of the sensor determine the total light energy used to make a photo and the resulting shot noise in that image.
The above "if, then" arguments misrepresent the process one should use to select shutter speed. ISO isn't a factor. Creatively, shutter speed controls how movement is rendered. Technically, shutter speed is an exposure setting. The slowest shutter speed that reliably renders movement to your liking without blowing out important highlights is the optimal choice.
Similarly, f-stop is the setting we use to control depth of field and the second camera setting that determines exposure. The widest lens aperture that produces an acceptable depth of field (DOF) without blowing out important highlights is the optimal setting.
The above "if, then" arguments are better presented as follows:
Static Subject Photography
subject, available light (minimum DOF) -> f-stop, (desirable amount of motion blur and optimal exposure) -> shutter speed. Select an ISO to manage image lightness
Dynamic Subject Photography
subject, available light (desirable amount of motion blur) -> shutter speed, (minimum DOF and optimal exposure) -> f-stop. Select an ISO to manage image lightness
Notes:
* One side-effect of (mostly) wanting a correctly exposed image is that using a faster aperture does not reduce the image noise in itself. As, without changing ISO, to end up with a correct exposure when getting 4x the light from a faster aperture will mean reducing the shutter speed to give 1/4 the time and cancel that out (or it would be 4x too bright). The faster aperture is only useful when it allows you to reduce the ISO setting, so to capture more light and have less noise.
Again, you're attributing a causal role to ISO that it does not have. Opening the lens (choosing a faster f-stop) does increase exposure. More total light energy will be delivered to the sensor. Signal-to-noise ratio (SNR) will be increased. This is true, regardless of the ISO in use.
ISO is used to manage post exposure image processing to achieve a desired image lightness. If the processed image is blown out, use a lower ISO. If ISO is already at base, blown highlights are an exposure issue. The solution is an adjustment to an exposure setting: f-stop or shutter speed.
* Also widening the aperture is only okay if you still end up with enough Depth of Field, and on long lenses that can go away quite quickly.
We typically use longer lenses to photograph subjects at greater distances or to isolate the subject. The increased magnification and ppotentially shallow depth of field are advantages; they're reasons why we buy and use long lenses.
* Some people still don't use Ev to measure scene brightness, but I think it's really become generally used for that these days so I do.
I'd speculate a majority of photographers don't measure scene brightness in any manner. The handheld light meter has become an anachronism. In-camera meters and histograms indirectly indicate scene brightness and then only at base ISO. They're always indicators of image lightness.
This doesn't make it any less useful to have an understanding that scene brightness is a factor determining exposure and that more light (a brighter scene) is generally a good thing...but not always.
I don't assign a numeric exposure value to scene lighting. I doubt many photographers do. It's not necessary to making a good photo.
* Some people don't like calling Photon Shot Noise, well, Noise, rather than just being a feature of the light.
To flesh that out a bit, shot noise is naturally occurring randomness in light.
However as it appears as noise to the photographer I'm happy with calling it Noise.
That's what it is.
* I have no problems with what "some people" (used to suggest a minority) choose to do and wasn't being derogatory, just pointing out my choices used in the above.
* The ISO effect is baked into the Raw file, so you're stuck with it.
However a manufacturer chooses to implement ISO in-camera, that doesn't make it an exposure setting or a source of noise.
even when they were noisy, I was still happy I got to see the owl in the first place!
