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09-10-2015, 06:57 AM   #1
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Help - my photos suddenly look mosaic

Hi everyone -

Up until a few weeks ago, my photos were looking good, but now I'm getting this weird mosaic-looking effect on all of them and I don't understand why.

The top image is the full photo, the second image shows the weird effect. What I do know is that the weird effect isn't caused by zooming in or increasing the image size.

Any help or suggestions would be great appreciated.

- Anthony



09-10-2015, 07:11 AM   #2
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it looks like compression from jpg settings - do you shot in jpg format?
09-10-2015, 07:16 AM   #3
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QuoteOriginally posted by Murfy Quote
it looks like compression from jpg settings - do you shot in jpg format?
JPG, Yes.
09-10-2015, 07:18 AM   #4
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Anyway you can post a full sized photo somewhere? Or at least the exif data and camera settings.

09-10-2015, 07:23 AM   #5
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QuoteOriginally posted by Anthony Quote
JPG, Yes.
I am thinking a setting was changed. I am not sure what camera you use, I may have missed that, but the K-3 has different jpg quality and size options, so it may have been switched accidentally from the highest size and quality
09-10-2015, 07:37 AM   #6
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Do you mean the dots in your image? If so, see what ISO you're at.
09-10-2015, 07:42 AM   #7
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Anthony, in order to give a proper answer we need the full EXIF details for that photo. At the very least: what camera, lens, shutter speed, aperture and ISO you used. And what camera mode you used: Av, Sv or Auto or ?
You should also check the jpg quality settings and make sure they are on best. However, I suspect your ISO has gotten set very high, either set that way or because you are using Auto and the camera selected it.

Anyway, post the information or the EXIF and I think we can get you fixed up.
09-10-2015, 07:51 AM   #8
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The full-size original image can be found here: http://i.imgur.com/bbFYpJi.jpg

Camera: Pentax K-50
ISO: 6400
Lens: Pentax 18-55
Camera Mode: SCN

09-10-2015, 08:02 AM   #9
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thanks, the problem in this case is the high iso. And as you state scn mode its probably choosen by the camera. Unless you are in iso manual and have set it to that level?
The higher the ISO the more grain you get in your pictures.
There is always a trade off between aperture, shutter speed and ISO. try to use another mode and learn how to set those your self. You got a DSLR and thus you could do more by picking the setting you want or try the P mode.
P mode is like auto mode but you can interact and change the settings. Play around and try different combinations. And learn how to compensate for the other.
Ther is two different iso modes. 1. Manual you set your desired ISO value yourself. 2. Auto you can change the range this mode is allowed to use. Read the manual... :-)

Last edited by max_pyne; 09-10-2015 at 08:17 AM.
09-10-2015, 08:23 AM   #10
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QuoteOriginally posted by Anthony Quote
Camera: Pentax K-50 ISO: 6400 Lens: Pentax 18-55 Camera Mode: SCN
Anthony, your answer is in ISO = 6400. That is going to cause the graininess or mosaic look you are seeing. The higher the ISO the more grain. Everyone has a different tolerance for this and you need to figure out what yours is. I rarely if ever go over ISO 400 because my tolerance is very, very low. I know others often shoot at ISO 1600 and above. But 6400 is pushing things on that sensor.

There are ways to help but they involve shooting in RAW and developing the picture on the computer, applying noise reduction there. But even with a good develop workflow ISO 6400 is pushing the limit for your camera.

I would recommend to start using the camera in one of the modes that allows more control. For example use Av mode or P mode and select the aperture you want and the ISO you feel comfortable with. Using the SCN modes just allows the camera to decide what will produce the best exposed image. In this case it used ISO 6400 to do that, and it achieved a nicely exposed images at the expense of a lot of noise. As noted above, sometimes you DO have to read the manual Another good resource is a book called 'Understanding Exposure' by Brian Peterson.
09-10-2015, 08:32 AM - 1 Like   #11
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I think the real problem begins with letting that child drink a lime-a-rita with her juice box.
09-10-2015, 08:49 AM   #12
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The higher the ISO number, the more digital noise is in the photo. The K-50 is actually pretty good regarding high ISO noise, some cameras, especially older ones or phone cameras, are much worse. At ISO 100, you will have next to no digital noise, though. Digital noise occurs naturally as you increase sensor sensitivity.
Anyway, to combat this, there is a Noise Reduction setting. This is an algorithm that tries to remove the noise. In some way, it can be successful, but it can also blur out some tiny detail. This is why NR is a setting, so you can leave it at Auto or choose your own option, depending on whether you want more noise reduction (less noise, but possibly less detail) or not so much noise reduction (more, sharper detail, but also some noise).

You can try to get a lower ISO by using a longer exposure (shutter speed like 1/60, 1/20), but this risks handshake and movement blur. You can lower ISO by using a bigger f-number (aperture, for example f2.8 or f1.4), but not all lenses are capable of very bright apertures, and a smaller f-number causes a more shallow Depth of field (the field that is sharp, and on-focus).

Since you shoot jpeg, I suggest you use the Portrait mode, fiddle with NR settings, and use a low f-number and slow shutter speed.

If you resize the jpeg photos to a smaller size, then a lot of the perceived noise will disappear. So if you take a 16MP photo and reduce it to 800 pixels on the long side, the photo will appear to be cleaner. So don't worry about some noise if you are planning no resizing the images for email or web use.

Jpeg compression can also appear to cause blockyness, but in a slightly different way. Usually as posterization or artefacts around edges. But I don't think this is the problem in this case. Just letting you know that you can also choose the level of compression in-camera. More compression means smaller files, but lower photo quality. Less compression means more quality, sharper images with more colours, but bigger file size. Once you compress a jpeg, you cannot "uncompress" it, and even re-compressing it will usually lower image quality without actually further decreasing file size. The only time you want to compress an image again, is if you start with a top quality source (like raw .dng file)

Just one more thing, Slow Shutter NR (or long exposure, dark frame NR) is different and only applies on exposures that are at least a couple seconds long. So this option is not relevant for most photography.
09-10-2015, 09:07 AM   #13
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You guys are awesome. Thanks so much! I'll report back later after I give these a spin.
09-10-2015, 09:50 AM   #14
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Yes I do agree with the iso, I probably I should have not jumped to the jpg setting. I also see posts in a lightroom group and usually the issue is too small file size, but it's worth checking out too.
09-10-2015, 09:53 AM   #15
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ISO: 6400 <------- this
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