a few years ago, my canon was replaced by canon with a canon PowerShot SX60HS and until recently has done well. Now, there is an issue with photos coming out grainy, As an example, the Blue Heron was taken at a further distance than the Merganser but the merganser photo is really grainy. Both were taken with the same settings at the same time of day.
I suspect the problem was caused in the second picture by the wrong camera settings.
In the first picture, you have plenty of light falling on the subject and you have good image quality.
In the second picturethere appeares to be less light falling on the sensor causing a loss of image quality. This can happen if the iso is set too high to compensate for a very fast shutter speed. Max iso with low light will reduce image quality. I also suspect there may have been some camera shake or digital zoom involved. Also if you cropped a lot this will show up more imperfections.
I feel you will get better results by trying the following.
1- If you have good light try using the P (Programme) setting. This will enable you to shot raw (or raw + jpg) to enable you to improve image quality. The in-camera jpg's sometimes look oversharpened which can create artifacts. You can avoid that by shooting raw and developing the picture yourself in Canon DPP or whatever software you choose. Using P mode will automaticaly select the best settings for the shooting conditions.
2- If you are shooting in manual mode check that you are not maxing the iso which will cause grain. You might need a wider aperture (lower F-Number) and a slower shutter speed and less iso. But you don't want a very show shutter speed to avoid camera shake.
3- Improve stability at high zoom by using the eyepiece instead of the lcd screen. Your head will help to stabilize the camera. Also if you don't have a tripod, lean the camera against a tree or other opject.Get as close as you can to the subject to avoid cropping too much in post production.
Of course, without knowing the exact camera settings, I am only taking an educated guess about what might have happened.
It can be very annoying when you miss a good picture. I do hope you were able to get some better shots of the Merganser another time.
My ISo is usually at 200. The Heron should have had less light since the trees were covering it and the Merganser was right out in the open. Using the Viewpiece is not an option for me. Because of the type of glasses I wear. the LCD screen works better for me. Normally my settings are on manual with an iso of about 200.
200 iso will give you decent pictures in good light. My only other thought is that the Merganser shot has digital zoom or is heavily cropped. There is also the possibility of camera shake but that would not explain the grain*. Generally you can remove most of the grain with software. But you can't do much with camera shake. It would help if its possible to get nearer to the subject. Thats easier said than done with wildlife photos.
* The in-camera jpg conversion produces sharpening artifacts which are distracting at high magnifications. That's why I prefer to shoot raw.
Thanks for the extra information. Your settings and camera technique seem to be just fine.
In that case, the grainy effect and lthe loss of image quality is possibly caused by excessive cropping, digital zoom and jpg sharpening artifacts. Sharpening artifacts can often look like coarse grain.
If its possible to post the original file somewhere it will be easier to check.
If there was líttle post cropping, then I would suspect the poor image quality is due to in-camera digital zoom and jpg artifacts. In retrospect, shooting raw would give you a better starting point and avoid the jpg artifacts. In "P" mode I think digital zoom is disabled. If just the optical zoom is used, you can later upsize the image online* or with other software to get much better results compared to digital zoom.
* eg. https://deep-image.ai/