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| Digital zooms v optical zooms | Rate Topic |
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| Posted by Eric: Tue Nov 27th, 2018 13:04 | 1st Post |
| I confess I have never liked digital zooms. Every camera I have owned that had this extra range extension beyond its optical limits had the feature turned off. I have always thought it was preferable, if not better,to capture the image with the optical lens available and crop the image to the size required in the computer. But today I have had my thinking challenged and would value your comments on my logic ( or not!). There is no doubt that using a digital zoom ( lets call it camera lens cropping) and sectional enlargement of your image after capture ( let's call that computer cropping) inevitably lead to some degree to a loss of sharpness. The extent and differences in methods being a function of camera sensor resolution and technique. But what about noise? A friend showed me some images today, taken on a bridge camera at 1600iso at 400mm optical and 800mm digital. There was some noise there in both images. ( we forget how blessed we are with Nikon DSLR high ISO control) However, taking the 400mm capture to the computer and cropping made the grain more noticeable....by virtue of the fact the grain was being sectionally enlarged as well as the subject. In fact the digital zoom image was all round a better image as shot. It leads me to re-evaluate my opinion of the usefulness of in camera digital zoom features. I PRESUME, that using the DX crop feature in an FX body won't have the same benefit? Because you are using a reduced area of the sensor as opposed to making the image bigger on the sensor by zooming? Interesting argument for getting it as big as possible in the camera by whatever method ....as opposed to relying on after cropping in a computer....particularly in high iso situations. 
____________________ Eric |
| Posted by Robert: Tue Nov 27th, 2018 13:39 | 2nd Post |
| Your term "Lens Cropping" I believe is misleading. I assume the optical zoom image and the sensor/processor zoom images are both the same pixel dimensions ie. not cropped in camera. I have never owned such a camera but my expectation is that the image processing directly from the sensor will be interpolating the image file at RAW level to the desired crop, then processing it into a full size JPEG or TIFF image for output to the SD card. Am I right in expecting the sensor/processor zoom only functions at set ratios? Is not infinitely variable? Like X2, X4, X6 etc. If that is the case and it might even be infinitely variable, using clever algorithms, then the sensors image processor is sharing the digitally cropped image among the entire available pixel map. Given this is taking place at RAW data level, prior to being formatted as JPEG or TIFF, I am not surprised the quality is acceptable, also, I assume the bridge camera is relatively high resolution, it wouldn't work well with a D1 2.4Mp image!!! Although, it was common practice to 'stretch' low res image to make them acceptable to publishers who seemed obsessed with high resolution images, that was usually done in certain set ratios which worked well with the original image mapping. Forgot to mention, a lot happens to the image data in the image processor beyond simply being formatted into the final data format, JPEG etc. If the pixel interpolation takes place first, in the image processor, then the other processes follow, they can even out the image and correct for stretching and re-sizing. Thus making the enlargement less obvious, smoother than it would be if done during post processing in a computer.
____________________ Robert. |
| Posted by jk: Tue Nov 27th, 2018 13:42 | 3rd Post |
| My understanding of digital zoom (dz) in bridge cameras is that the dz is just same as the way it is implemented in a FX DSLR. The same optical image is used but the section is interpolatted to give a zoomed image. So the same as doing a DX crop on an FX sensor. I may be wrong or the implementation may vary between camera makes.
____________________ Still learning after all these years! https://nikondslr.uk/gallery_view.php?user=2&folderid=none |
| Posted by Robert: Tue Nov 27th, 2018 14:07 | 4th Post |
jk wrote:So the same as doing a DX crop on an FX sensor. Will produce just that, a smaller image. I am assuming the output image from Eric's digitally zoomed camera is the same pixel dimensions as a standard image from that camera. Edited for clarity.
____________________ Robert. |
| Posted by Eric: Tue Nov 27th, 2018 14:21 | 5th Post |
jk wrote:My understanding of digital zoom (dz) in bridge cameras is that the dz is just same as the way it is implemented in a FX DSLR. The same optical image is used but the section is interpolatted to give a zoomed image. So the same as doing a DX crop on an FX sensor. The file size is the same for both the optical zoomed and the digitally super zoomed versions...is that the same for DX crop?
____________________ Eric |
| Posted by Robert: Tue Nov 27th, 2018 14:33 | 6th Post |
| Without going too far off topic... Eric, you mentioned higher ISO, I think that is quite unrelated to digital zoom. The advances in high ISO and related noise management utilise various techniques. In the past the signal from the sensor was amplified and therefor showed a very faint dark image more boldly and brightly, revealing shadow detail. Modern cameras with extremely high ISO compared with what we remember, utilise additional processes because you can only go so far with amplification, noise sets in. Think layering in PS, layer the same image ten times and use the add to multiply command. That is a technique used for astro photography which avoids long exposure and high ISO. What modern cameras are doing is effectively layering the image data instead of amplifying it. I understand the threshold is about ISO 3,200 then this 'layering' process kicks in. If you push the camera ISO too far, you limit what can be done in post process, the camera ISO boost is across the board, in post process you can just push the shadows, if the whole image has been pushed in camera, you may still have dark shadows with no latitude left for further adjustment, whereas if you push less in camera then you have more scope to just push the dark shadows in in post process (computer).
____________________ Robert. |
| Posted by Eric: Tue Nov 27th, 2018 14:35 | 7th Post |
Robert wrote:Your term "Lens Cropping" I believe is misleading. I assume the optical zoom image and the sensor/processor zoom images are both the same pixel dimensions ie. not cropped in camera. Sorry for misleading you Roberto.  I haven't tried this myself yet so am posting before fully thinking it through  The digital zoom is merely an extension of the normal zoom range. On Mikes camera the optical range ends at 400mm...with a flick of a switch, this continues upto 800mm seamlessly. As JK says, it's probably just interpolation but the resultant files are identical size. But cropping the 400mm version to 800mm shows more noise than the out of the camera 800mm.
____________________ Eric |
| Posted by Robert: Tue Nov 27th, 2018 14:39 | 8th Post |
| Because the interpolation happens in the camera with straight from the sensor RAW data, not JPEG or TIFF data in the computer.
____________________ Robert. |
| Posted by Robert: Tue Nov 27th, 2018 14:41 | 9th Post |
Eric wrote:Sorry for misleading you Roberto. I'm easily misled! 
____________________ Robert. |
| Posted by jk: Tue Nov 27th, 2018 16:36 | 10th Post |
| So that we can actual talk facts...... What wasthe make/model of your friend's bridge camera? I think that most bridge cameras can produce RAW or JPG. Do you know which was being used?
____________________ Still learning after all these years! https://nikondslr.uk/gallery_view.php?user=2&folderid=none |
| Posted by jk: Tue Nov 27th, 2018 18:12 | 11th Post |
| From wikipedia.... https://en.m.wikipedia.org/wiki/Digital_zoom Digital zoom is a method of decreasing the apparent angle of view of a digital photographic or video image. Digital zoom is accomplished by cropping an image down to a centered area with the same aspect ratio as the original, and usually also interpolating the result back up to the pixel dimensions of the original. It is accomplished electronically, with no adjustment of the camera's optics, and no optical resolution is gained in the process.[1] When comparing the image quality achieved by digital zoom with image quality achieved by resizing the image in post-processing, there's a difference between cameras that perform potentially lossy image compression like JPEG and those that save images in an always lossless Raw image format. In the former case, digital zoom tends to be superior to enlargement in post-processing, because the camera may apply its interpolation before detail is lost to compression. In the latter case, resizing in post-production yields results equal or superior to digital zoom.
____________________ Still learning after all these years! https://nikondslr.uk/gallery_view.php?user=2&folderid=none |
| Posted by Robert: Wed Nov 28th, 2018 03:37 | 12th Post |
jk wrote:From wikipedia.... https://en.m.wikipedia.org/wiki/Digital_zoom More or less what I said... Only they probably took longer to compose the text.  Is this being explored as a Yorkshire alternative to a Z7 and the 500PF? If so I think it will win the Yorkshiremans prize for thrift but fail big time on IQ. Two zooms, one of which digital, on a bridge camera will never approach the quality of the 500PF (+ X1.4?) and cropping the Z7 (or D850). Straight logic, why would anybody buy the expensive option if the cheap option would even, almost get the job done.
____________________ Robert. |
| Posted by jk: Wed Nov 28th, 2018 06:59 | 13th Post |
| Re: "If so I think it will win the Yorkshiremans prize for thrift but fail big time on IQ. Two zooms, one of which digital, on a bridge camera will never approach the quality of the 500PF (+ X1.4?) and cropping the Z7 (or D850)." Agree with Robert. Eric, you only live once, never compromise the quality for the sake of a few pence/pounds. You know you are worth it!  Enjoy the Z7/D850 and 500mm. I still think the 200-500mm f5.6 AFS VR rather than 500mm f4 PF AFS is a better purchase as it gives more flexibility.
____________________ Still learning after all these years! https://nikondslr.uk/gallery_view.php?user=2&folderid=none |
| Posted by Eric: Wed Nov 28th, 2018 14:22 | 14th Post |
| Who said anything about ME changing my intentions? I merely said that images presented to me from a bridge camera exhibited less visible noise when digitally zoomed than when cropped on a computer and this may have changed my opinion of digital zoom. The camera was the LUMIX FZ1000 shooting in raw, by the way. My wife already has the later FZ2000 (in many ways a superior camera) and when I have a moment I will do the same comparison with her camera that mike did on his camera. I STRESS, the image sharpness does suffer ( equally with digitally zooming or cropping afterwards) and for this reason I wouldn't countenance choosing it over a prime lens, larger sensor and more pixels. I just feel it's interesting that high ISO noise appears to be less intrusive on a digital zoom. As I haven't got Mikes images to post I will take some shots on the FZ2000.... while I wait for my Z body and 500mm to be delivered. ( on recent Nikon delivery performance I have many weeks to effect this comparison 😡)
____________________ Eric |
| Posted by Robert: Wed Nov 28th, 2018 14:39 | 15th Post |
Eric wrote:I just feel it's interesting that high ISO noise appears to be less intrusive on a digital zoom. It may be that further noise reduction takes place after or even during, the interpolation process. From that point of view, I think 'in camera processing' can be superior to post processing, because it's very camera specific and also image specific.
____________________ Robert. |
| Posted by Robert: Wed Nov 28th, 2018 14:39 | 16th Post |
Eric wrote:I just feel it's interesting that high ISO noise appears to be less intrusive on a digital zoom. It may be that further noise reduction takes place after or even during, the interpolation process. From that point of view, I think 'in camera processing' can be superior to post processing, because it's very camera specific and also image specific.
____________________ Robert. |
| Posted by Iain: Wed Nov 28th, 2018 15:26 | 17th Post |
| I was going to say it must have been one with a 1" sensor as my Panasonic fz330 digital zoom is useless mine I have to say I am disappointed with it full stop. I should have kept my Canon hs50 as the iq was much better.
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| Posted by jk: Thu Nov 29th, 2018 04:51 | 18th Post |
| Which Z did you go for Eric? Z7 or Z6. The 500mm will be great as you know but I will be interested to hear how you like/dislike the Z.
____________________ Still learning after all these years! https://nikondslr.uk/gallery_view.php?user=2&folderid=none |
| Posted by Eric: Thu Nov 29th, 2018 14:06 | 19th Post |
jk wrote:Which Z did you go for Eric? Z7. I've had a brief look at the digital zoom on the FZ2000. Need to talk to Mike about his results because on THIS model you cannot use digital zoom when shooting Raw,
____________________ Eric |
| Posted by Iain: Thu Nov 29th, 2018 15:32 | 20th Post |
| That's the same as my fz330 Eric.
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| Posted by Robert: Thu Nov 29th, 2018 16:56 | 21st Post |
Eric wrote:jk wrote: But that wouldn't matter, the interpolation and adjustments will be made BEFORE the as shot RAW image is converted to TIFF or JPEG so the output should be pretty much the same except you won't have as much latitude for post processing.
____________________ Robert. |
| Posted by Eric: Fri Nov 30th, 2018 14:37 | 22nd Post |
Robert wrote:Eric wrote: Except you have to accept the cameras jpegging artefacts....which can be more significant a contribution with smaller sensor, high iso situations, With raw, you have the opportunity to evaluate the image without any camera compression interference. But it's a bit academic cos you can't do it. I think one of the distracting influences here is that cropping images from these sensor sizes is always risky. The IQ rapidly disappoears. Fill the frame and the images are great but cropping soon shows the limitations. I guess that's why filling the frame with a digital zoom may be better than cropping....the interpolation may be helping!
____________________ Eric |
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