G5x Digital teleconverter vs crop

After years with my G11 I bought a PowerShot G5x and love it. I  miss a bit the longer optical zoom of the G11 but here is where my question comes in:

When do I use the 1.6 or 2.0x digital Tele converter, and more importantly what does it do to the image quality? Would I get a better quality result taking an image at the 4.2 X optical zoom and then crop it to the view I would get with 1.6 or 2.0x tele converter? I have taken test images but have a hard time seeing a difference on a 20 inch computer screen. I am not enlarging images for printing, mostly view photos on computer or tablet (Microsoft Surface Pro 3) screens.

Comparing the test shots of the 2.0x tele converter to the 8.4x digital zoom suggests they have the same zoom factor, what is the difference, advantage and disadvantage between:

a) 4.2 optical zoom and crop in Photoshop Elements

b) 1.6 or 2.0x digital tele converter

c) 8.4 x digital zoom

Any insight and help is very appreciated,

Thanks,

Wolfgang

In fact, with the G5x you don't loose reach compared to the G11 : at 140mm (24x36 equiv) the G5x work with a 1/1.4" 10Mpixel sensitive area and a 36.8mm lens while the G11 work with a 1/1.7" 10Mpixel area and 30.5mm lens !

teleconverter vs digital zoom : the former is available on all focal length (so you can use it while keeping the focus distance at the closest position and have better magnification in macro for example). Digital zoom is more convenient for reach purpose.

crop vs teleconv or digital zoom : from jpeg, the difference in quality is minimal if you keep the viewing size the same (the teleconv and digital zoom interpolate pixel to reach the definition set in the camera so comparison at 100% are misleading). Use teleconv or digital zoom if you don't want to post process your pictures

Thank you Olf for taking the time to post a response.

Unfortunately I do not understand the details of your first paragraph. I am a retired electrical engineer and this optical stuff is a bit "over my head" 

I think I get your second paragraph, as I also did some "trial and error" tests and noticed that in digital tele converter setting for example at 2x setting, the entire lens range is doubled, at the 24 mm wide angle I get 48 mm, and at the max zoom I get 200. If I understand your comment correctly digital zoom provides a better magnification at the wide angle setting (24mm), same as if I would use the optical zoom only.

The third paragraph goes over my head again, sorry. But if I get this right, I should use optical zoom only and crop in post processing (crop) with Photoshop Elements. I am not shooting RAW, too much work imho. I read that using digital zoom all the way (17 x or ~ 400mm)  has a big IQ impact. So, I would like to limit my use to either digital tele converter (2x setting) or digital zoom to a max of 8.4x, (yellow bar)  which would be the optical zoom times two. What I don't understand is if the IQ at the 2x tele converter setting is exactly the same as the "2x" going the digital zoom route to 84.x or do those two software tools use a different algorithm, resulting in one of the setting having a better IQ than the other? If so, which provides better IQ

If you have the time, and the patience with me, please elaborate on the third paragraph please.

Thanks,

Wolfgang

Wolfgang Dempke wrote:

Thank you Olf for taking the time to post a response.

Unfortunately I do not understand the details of your first paragraph. I am a retired electrical engineer and this optical stuff is a bit "over my head"

The G11 has a 28-140mm lens in front of a 1/1.7" 10Mpixel sensor.

The G5x has a 24-100mm lens in front of a 1" 20Mpixel sensor. When you crop from 100mm to 140mm, the remaining sensor area is 1/1.4" and 10Mpixel, same pixel count but bigger sensitive area.

So the G5x has no drawbacks compared to G11 in term of maximum focal length.

I think I get your second paragraph, as I also did some "trial and error" tests and noticed that in digital tele converter setting for example at 2x setting, the entire lens range is doubled, at the 24 mm wide angle I get 48 mm, and at the max zoom I get 200. If I understand your comment correctly digital zoom provides a better magnification at the wide angle setting (24mm), same as if I would use the optical zoom only.

Digital zoom only is applied past maximum optical zoom so it is only useful to have more reach for distant targets. It is convenient because it is accessible with the zoom rocker.

Digital teleconverter, has you said, is applied to the entire lens range. It is useful to add more magnification when you don't want to increase the optical zoom. I give the example of macro where the maximum magnification is not obtained with the maximum focal length as the minimum focus distance greatly increase when you zoom.

The digital teleconverter and digital zoom offer the same amount of magnification for the same quality. A picture taken at 100mm + 2x teleconverter will be exactly the same as one taken at 8,4x optical + digital zoom.

The third paragraph goes over my head again, sorry. But if I get this right, I should use optical zoom only and crop in post processing (crop) with Photoshop Elements. I am not shooting RAW, too much work imho. I read that using digital zoom all the way (17 x or ~ 400mm) has a big IQ impact. So, I would like to limit my use to either digital tele converter (2x setting) or digital zoom to a max of 8.4x, (yellow bar) which would be the optical zoom times two. What I don't understand is if the IQ at the 2x tele converter setting is exactly the same as the "2x" going the digital zoom route to 84.x or do those two software tools use a different algorithm, resulting in one of the setting having a better IQ than the other? If so, which provides better IQ

If you have the time, and the patience with me, please elaborate on the third paragraph please.

I advise to use in camera digital zoom or teleconverter mainly if you don't do post processing for convenience. If you do some post processing, crop is more versatile as it allows you to reframe more carefully.

Crop, digital zoom and digital teleconverter all have an impact on quality because you limit the pixel quantity and sensitive area from which the image is displayed.

At 200mm, for example, by cropping in post you stay at 5Mpixel while in camera, the device interpolate the picture to the definition you set (20Mpixel if L is selected), but in full screen, I don't think it makes a dramatic difference.

At 17x, you work with only 1,2Mpixel so the quality will be quite low. IMHO, the results are excellent at 160mm, good at 200mm, and acceptable at 250mm.

Thanks,

Wolfgang

Hello Olf,

Thanks again for taking the time to reply. Your "digging deeper" and keeping it simple for a beginner like me was VERY helpful. I do have now an understanding how digital zoom, digital tele converter and crop are related IQ-wise. Going forward I will use optical zoom plus PSE 12 crop or other editing in the majority of my shooting. I have programmed the C setting on my G5x to have a quick access to the 2x tele converter, just in case I want to zoom in a bit more while traveling and send the picture to a friend. I do not have PSE 12 on my Surface Pro 3 tablet/ laptop (menus are too tiny for my eyes) meaning I do all post processing on the desktop PC at home.

Thanks again, GREAT help as usual on the Forum. I marked your response as "The answer".

Wolfgang