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| Digital zooms v optical zooms - Page 1 | |
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| Posted: Tue Nov 27th, 2018 13:04 |
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1st Post |
Eric
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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 |
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| Posted: Tue Nov 27th, 2018 13:39 |
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2nd Post |
Robert
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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. |
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| Posted: Tue Nov 27th, 2018 13:42 |
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3rd Post |
jk
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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 |
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| Posted: Tue Nov 27th, 2018 14:07 |
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4th Post |
Robert
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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. |
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| Posted: Tue Nov 27th, 2018 14:21 |
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5th Post |
Eric
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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 |
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| Posted: Tue Nov 27th, 2018 14:33 |
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6th Post |
Robert
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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. |
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| Posted: Tue Nov 27th, 2018 14:35 |
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7th Post |
Eric
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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 |
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| Posted: Tue Nov 27th, 2018 14:39 |
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8th Post |
Robert
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Because the interpolation happens in the camera with straight from the sensor RAW data, not JPEG or TIFF data in the computer.
____________________ Robert. |
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| Posted: Tue Nov 27th, 2018 14:41 |
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9th Post |
Robert
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Eric wrote:Sorry for misleading you Roberto. I'm easily misled! 
____________________ Robert. |
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| Posted: Tue Nov 27th, 2018 16:36 |
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10th Post |
jk
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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 |
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