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03-10-2017, 03:30 AM   #46
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QuoteOriginally posted by BarryE Quote
Do we have to get hung up about all this. Most of us know that adding and removing pixels via any of the resampling/interpolation algorithms changes the image. Processing can then correct this, somewhat. This is why the adding/removing pixels is done at the start of a workflow. Just changing the the image so it will print differently changes nothing - no pixels are harmed in this process. We know this.

Noise is noise. It is worked out of an image in many ways via intelligent processing - not just sliding a slider here and there. Best not to get it in the first place, but it is often overrated. (Noise can be, however, very effectively used to good effect.) Often noise is the result of high ISO being used - high ISO kills the dynamic range. This personally is why I don't like high ISO, not noise, but what it does to the dynamic range. DR can be carefully eased back into an image with curves and masks etc, but it is less than idea.

Get it right in camera, wherever possible, then process the problems away where possible.

Keeping noise down generally - in forums too - is a good idea ;-)
I think the point is that noise visibility depends on a couple of factors. Obviously the iso used combined with light level shot are important factors. But size an image is viewed is important as well. If you can actually see the individual pixels, then you are much more likely to notice noise in your final image. If, on the other hand there is some sort of binning or averaging going on with the pixels to form the final image, then the noise will not be as noticeable.

Dynamic range is related to noise in that it has to do with the level for a given iso that you can bump the shadows before the noise becomes noticeable.

Resampling for printing or for viewing is not magic, but there is no doubt that it does make images look a lot better than if you zoom in to 100 percent.

03-10-2017, 04:22 AM   #47
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QuoteOriginally posted by Rondec Quote
I think the point is that noise visibility depends on a couple of factors. Obviously the iso used combined with light level shot are important factors. But size an image is viewed is important as well. If you can actually see the individual pixels, then you are much more likely to notice noise in your final image. If, on the other hand there is some sort of binning or averaging going on with the pixels to form the final image, then the noise will not be as noticeable.

Dynamic range is related to noise in that it has to do with the level for a given iso that you can bump the shadows before the noise becomes noticeable.

Resampling for printing or for viewing is not magic, but there is no doubt that it does make images look a lot better than if you zoom in to 100 percent.
DR is really dependent on the amount of light that is gathered from the exposure. Increase the iso by 1 stop you decrease how much light the sensor can store by 1 stop. If you decrease the amount of light that is captured then the size of the image that you can view it without seeing noise decreases. You also have to remember the majority of the noise you see in an image is that of shot noise ( how light its self randomly falls on the sensor) with increased resolution you can see how that light randomly falls on the sensor and this appears as noise ( the variation from pixel to pixel ). If you have enough signal then that variation is not seen pixel to pixel, when you decrease the signal then you have a greater chance of see that variation from pixel to pixel starting in the areas that are made up from less light ( the shadows)
03-10-2017, 04:28 AM   #48
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The other thing about noise is that it results in much bigger jpegs.

Most non-pro people either shoot and keep only jpegs, or they use e.g. Lighroom to process the RAWs and then export into jpegs and discard the RAWs.

If you shoot an image at relatively high ISO (say 500 for the K3 or 2000 for the K1) and then export to jpeg at some fairly high quality (I use 95% in LR) you end up with say a 15MB jpeg. But if in LR you used the noise reduction slider (NR in Luminance) and moved it to about 25%, that will remove the noise (as seen at 1:1) with a minimal loss of sharpness and the jpeg will be say 5-10MB and it will look exactly the same for all practical purposes. Most of the excess size of the jpeg was compressing (unsuccessfully) the very small noise spots.

Many will say storage is cheap but when your photo collection gets to a few hundred GB then backups get "interesting". I rotate half a dozen 2TB USB drives via an off-site fire safe but there are issues with that too. Also viewing images is faster.

Interesting to hear the K5 had the same pixels as the K1. I don't recall noticing any special low light performance.
03-10-2017, 04:50 AM   #49
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QuoteOriginally posted by clackers Quote
Well, you're quite wrong again, Gimbal ....

"When changing the size of an image in Photoshop, there's really two ways to go about it. You can either resize the image, or you can resample it. A lot of people use the terms resizing and resampling as if they mean the same thing, but they don't. There's an important difference between the two."]
Resize according to Adobe is nothing more than changing the dpi setting, which means that they leave the actual resizing of the image to the printer driver.

The printer driver will up/down scale the image according to the dpi setting and the most suitable resolution for the printer. The driver will NOT use the simple throw away pixel algorithm you described. No one does.

So I guess you were wrong again, Clackers.

03-10-2017, 08:05 AM   #50
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That might be true for printing (and scaling to print at different sizes) but it isn't the case for a normal image resizing process in photoshop. They use something more clever.
03-10-2017, 08:23 AM   #51
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Absolutely, resizing ”always” includes some sort of up/down sampling of the image. It’s never a question of simply throwing away unwanted pixels.
03-13-2017, 08:28 PM   #52
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QuoteOriginally posted by leekil Quote
I'm not sure what in your reference you think supports your original statement about resizing via simply dropping pixels? Can you be more explicit?
Of course, @leekil

You can read here about the problems inherent to Resampling. It's an art.

http://designer-info.com/Writing/image_resample.htm

Last edited by clackers; 03-13-2017 at 08:41 PM.
03-13-2017, 08:37 PM   #53
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QuoteOriginally posted by Gimbal Quote
Resize according to Adobe is nothing more than changing the dpi setting, which means that they leave the actual resizing of the image to the printer driver.

The printer driver will up/down scale the image according to the dpi setting and the most suitable resolution for the printer. The driver will NOT use the simple throw away pixel algorithm you described. No one does.
But that is what you want in your workflow, @Gimbal

Listen to Barry and the others.

You will resize not downsample as you go through all your postprocessing steps. You don't want any downsampling until the last possible step, because it causes deterioration of the image.

The golden rule is to get the cleanest, best, biggest RAW file manageable (that is what DxOMark's Screen Tab measurements are about) then do the least damage to it in output.

This is not a hard idea.

03-14-2017, 02:42 AM - 1 Like   #54
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QuoteOriginally posted by clackers Quote
But that is what you want in your workflow, @Gimbal

Listen to Barry and the others.

You will resize not downsample as you go through all your postprocessing steps. You don't want any downsampling until the last possible step, because it causes deterioration of the image.

The golden rule is to get the cleanest, best, biggest RAW file manageable (that is what DxOMark's Screen Tab measurements are about) then do the least damage to it in output.

This is not a hard idea.
Of course. But the question is if you have a K5 image at iso 1600 and a K-1 image at iso 1600 (or whatever iso) and you print both of them to an 8 by 10, can you tell the difference. What I have found is that after iso 800 the K-1 image will look better. Downsampling or not, you just see the noise in the K5 pixels more easily than you do in the K-1 image and at a certain iso level, it really starts to make a difference. The end result is that you have a little better than a stop improvement in iso you can shoot for the same size printing.
03-14-2017, 08:38 PM   #55
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QuoteOriginally posted by Rondec Quote
Of course. But the question is if you have a K5 image at iso 1600 and a K-1 image at iso 1600 (or whatever iso) and you print both of them to an 8 by 10, can you tell the difference. What I have found is that after iso 800 the K-1 image will look better. Downsampling or not, you just see the noise in the K5 pixels more easily than you do in the K-1 image and at a certain iso level, it really starts to make a difference. The end result is that you have a little better than a stop improvement in iso you can shoot for the same size printing.
I think that matches closely with what I said in post 32, Vincent:

So if you're not just resizing, you're also doing some sort of postprocessing that includes downsampling, in poor light conditions you'd expect to see about a stop's difference between your K-5 and K-1. Alright, it destroys details too, but the idea is that details aren't random, noise is, and so to a point, averaging is desirable.

You can see from my night concert shot above, I think it was worth my money to chase that marginal improvement.


Just in this thread, Mee and BarryE seemed a little underwhelmed by the K-1 vs APS-C images they've taken at good light levels, and Rupert thought even at poor levels.

Expectations must be understood by looking at the RAW files and their SNR and Dynamic Ranges, which is DxOMark's Screen tab.

Biz-engineer found the pics hard to tell apart at ISO 400 ... these pics, like all JPEGs, have certainly been downsampled. See if you think one is twice is good as another!

K-1 vs K3, which is which - PentaxForums.com

And even at ISO 6400, you can see if that's also true in the famous Imaging Resource RAW files:

The superiority of FF over APS-c re: Depth of Field - Page 12 - PentaxForums.com
04-21-2017, 03:31 PM - 1 Like   #56
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I had some photos I took at a wedding developed and received them this afternoon. The setting was indoors in a building without windows (no outside light and just minimal overhead light) so it was quite dark! I had no flash on the K-1. Only option was to increase the ISO... 3200.. 6400.. heading into territory that made me gulp.

Even then I had to bump up the exposure in post by half to 1 and a half stops.

On screen they are rather noisy despite running through DXO Prime noise reduction and then another masking attempt... noisy but passable.

In print (glossy 5x7), they look very nice! 5x7 is pretty small.. but I was still expecting to see quite a bit of grain. Nope.

That gives me a bit more confidence in increasing the ISO now. I wonder how big I can print and at what ISO setting before it becomes a problem.. that will be determined through a series of test prints now.
04-21-2017, 05:49 PM   #57
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QuoteOriginally posted by mee Quote
On screen they are rather noisy despite running through DXO Prime noise reduction and then another masking attempt... noisy but passable.
If you are still seeing the "white dots" issue you may want to try Capture One 10. It deals with "white dots" much better than LR and has a "Single Pixel" noise reduction slider with which you can choose how aggressively to remove the "white dots".
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