Ask Uncle Ronnie – MAY 2017

Nikon D5300

4K recording
What is the exact meaning of 4K recording @ 60 fps or 30 fps, Full HD 1080p @ 30 fps or 60fps etc. Please explain in detail.

Virag Sharan, Jaipur ( Rajasthan )

Almost all digital cameras today offer video shooting capabilities. Videos can be shot at the following resolutions:

1280 x 720 pixels [known as 720p, High Definition (HD)]

1920 x 1080 pixels [known as 1080p, Full High Definition (FHD)]

3840 x 2160 pixels [ known as 4K, Ultra High Definition (UHD)]

From the above, you will notice that it was the vertical resolution that was quoted for HD and FHD but was switched to the horizontal resolution for UHD.

When we say 1280 x 720 pixels, it means that each frame has 1280 pixels in width and 720 pixels in height. The letter ‘p’ stands for ‘Progressive’ (as opposed to ‘Interlaced’ or ‘i’), which means that the computer scans each line progressively. Simillarly, when we say 3840 x 2160 pixels, it means that each frame of the video has 3840 pixels in width and 2160 pixels in

Digital camera videos can be shot at different frame rates (example 24, 30, 60 fps). 24 fps is considered as the ‘standard’ frame rate (often called ‘cinematic’ rate). If you shoot at 60 fps and play back the video at 24 fps, it will appear like slow-motion. Some Ask your question to Uncle at people prefer 30 fps over 24 fps; it’s best to try the various fps and decide for yourself which you like better.

Pictures no longer sharp!
I used to get very sharp imges from my digital SLR camera, but now a days the pictures don’t seem to be as sharp as before. Moreever, I notice a loss of contrast too. Do digital cameras lose their sharpness and contrast with age?

D. S. Pai, Chennai, via email

Do you feel the loss of sharpness with any particular lens or with all lenses? There could be several possible reasons:

1. If with a particular lens, it is possible that a lens element could have been displaced slightly (due to very rough handling/or a sudden heavy jerk, though this type of problem is very rare).

2. If with all lenses – have you ever tried cleaning the reflex mirror? Cleaning the mirror is a very delicate operation, best left to competant camera technicians. Placing more than required pressure on the reflex mirror while cleaning can mis-align the mirror and cause issues with sharpness.

3. How old is your camera? Have you ever cleaned the imaging sensor? (Actually, when we clean the sensor, what we are cleaning is the antialiasing filter, also known as the Low-pass filter that is placed over the sensor). Over a long period of time, dust settling on the sensor can cause a loss in sharpness and your statement that there is also a loss of contrast makes me feel that this could be the issue. Please have the camera checked by a competant technician to ensure that this is not the cause of the problem that you face.

4. Improper cleaning of the imaging sensor can also damage it, but then the problem you face would be with all your lenses.

5. If the sensor is regularly cleaned – if there are no dust particles on it, and if the front/rear elements of the lens are clean, or if the filter over the lens is spotless, then a digital camera will not show any loss of sharpness/ contrast due to age.

Note: Some of us, including myself, avoid cleaning the sensor due to fear of damaging it. It is true that if you are not extremely careful while cleaning the sensor, or if you use the wrong kind of cleaning materials, you can damage it. But cleaning the sensor is important. No matter how careful you are when changing lenses, dust will eventually settle on to the sensor. If you are worried about damaging the sensor while self-cleaning it, I strongly advice you to take your camera to an authorised service station and have it cleaned. Yes, the service centre may charge you approx. Rs 1200/- or so for sensor cleaning but that would be money well spent.

Even after cleaning the sensor, dust could re-settle on it the very first time that you change the lens. Hence, change your lenses only when the wind is not blowing. Avoid changing lenses in dusty conditions. Don’t keep the camera body facing upwards for any length of time when there is no lens attached to it.