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New Contributor
Posts: 4
Registered: ‎07-30-2015

Re: Grainy Pictures

That makes a lot of sense thank you so much for the help!! Like I said before we know some but very very little about this kind of camera. Very much appreciated! 

New Contributor
Posts: 4
Registered: ‎07-30-2015

Re: Grainy Pictures

Alan

 

I just tried what you said and WOW did that help out a lot!! Thank you for putting it into step by step for us! Also The pictures that I posted were just taken very quickly to show the grain, we usually make it to where the reflection is not there lol!! But thank you for the help with that as well!

Highlighted
Esteemed Contributor
Posts: 3,815
Registered: ‎06-11-2013

Re: Grainy Pictures

You can find numerous videos on photographing shiny metal objects.

Here's a video that will help you with the basics: http://youtu.be/C8HNBcu3Hig

The watch dial is a bit different because you want to eliminate the reflection from the crystal but still see the face below. That usually calls for a circular polarizing filter to reduce the reflections.
Tim Campbell
5D III, 5D IV, 60Da
New Contributor
Posts: 3
Registered: ‎08-07-2018

Re: Grainy Pictures

Hello

 

I recently bought asecond-hand Canon 5D Mark 111

 

I have been shooting children at schools in AV format, but resulting in grainy images.  So i thought, clearly im getting my ISO wrong within the AV setting.  (Usually ISO 800 inside classrooms, and ISO 400 outside in playgrounds - f4)

 

So i put ISO on AUTO.  But i still am getting grainy images, as per the attached.  In fact, the grain in the image attached was worse in its original raw size (19 meg) - looking a little better in its small 2meg BRAN2392a.jpgsize actually.

 
What am i doing wrong do you think?  Surely the camera is clever enough to get this right?
 
ilonka
Esteemed Contributor
Posts: 3,407
Registered: ‎02-17-2016

Re: Grainy Pictures

That looks fine to me. Ken Rockwell shows that grain is pretty well controlled even at high ISO's:

https://kenrockwell.com/canon/5d-mk-iii.htm

 

You should probably start your own topic and attach a crop.

VIP
Posts: 11,341
Registered: ‎12-07-2012

Re: Grainy Pictures

A couple things.  Yous shot is slightly underexposed to my liking.  That will show more grain.  In general it is a good looking shot so I would not be concerned, just a 1/2 stop more exposure.

 

This is how you shot it if you were wondering because it isn't as you suggested.

f8, 1/40, ISO 1250 and FL of 32mm.  MPO is I never use auto ISO. Never!  That is P&S stuff if you want a P&S you don't need a 5D3. Set your ISO where you wnt it.

 

Using f8 and 1/40 I am pleased you got as good a shot as you did.

EOS 1DX and 1D Mk IV and several lenses!
New Contributor
Posts: 3
Registered: ‎08-07-2018

Re: Grainy Pictures

Hello

 

thank you for your feedback.

 

Youre absolutely right, that was the AUTO measurements.

 

I reverted back to controlling my ISO today, going lower than ever.  Whilst better , sadly i am still seeing some grain.  

 

Somehow i am not achieving the clarity im looking for.

 

Thanks for the feedback anyway.

ilonka

.

 

 

New Contributor
Posts: 3
Registered: ‎08-07-2018

Re: Grainy Pictures

I am still achieving grainy images :-(

 

I noticed a '!" onscreen when looking through my viewfinder. Could this be the cause?

 

Any thoughts?

 

VIP
Posts: 11,341
Registered: ‎12-07-2012

Re: Grainy Pictures

"I noticed a '!" onscreen when looking through my viewfinder."

 

My cameras don't have that but I think it means it can't achieve focus.  Your shots look pretty normal.  Slight underexposure but I think they are OK.

EOS 1DX and 1D Mk IV and several lenses!
Esteemed Contributor
Posts: 3,815
Registered: ‎06-11-2013

Re: Grainy Pictures

This is a change of subject since the original thread ... it’s often better to just create a new thread.

 

Anyway, in the image you posted, I am not seeing any noise ... which makes me wonder what you’re seeing.  I am specifically looking at the sock in the lower left corer (since that’s basically a black area).  If the image is noisy... that area should reveal it. But I’m not seeing it in this image (possibly due to resizing).

 

Re-sizing an image to a smaller size involves reducing more pixels into fewer pixels.  E.g. if you make an image half as wide and half as high, then that means each 2x2 cluster of pixels (4 pixels) will be reduced to just one pixel.  If ONE of those 4 pixels was excessively noisy it will get averaged out by the other three non-noisy pixels and this naturally reduces the noise.

 

To truly evaluate the noise, we’d need to see a full-size version of the image (preferably the RAW “.CR2” file since JPEG images are typically auto-processed to reduce noise.

 

 

 

So a bit about noise...

 

ALL cameras have noise.  But the reason you might see one image and think it has no noise and see another image and think it has a lot of noise has to do with something called the “Signal to Noise Ratio” (SNR).  

 

Basically the noise level remains somewhat constant... but it’s the signal level that varies.  If you don’t collect enough “signal” (good data) then the ratio is worse and you perceive a noisy image.

 

Exposure is based on ONLY shutter time and aperture size.  ISO is not part of “exposure” because ISO is an amplification of the data which occurs only after the shutter closes and the image is captured.  At that point any amplification is amplifying everything ... good signal and noise alike.

 

This is why people feel shots taken at low ISO don’t have noise and high ISO do have noise.  The reality is that the amount of noise is the same.  But in the low ISO shot, you either had more available light (good signal was arriving in abundance) or you allowed a larger aperture or longer exposure time until the camera collected enough signal... such that there was no reason to amplify the data.  That results in a high amount of signal relative to the noise (a good SNR) so the noise isn’t amplified and you don’t perceive it (even though it really is there ... every digital sensor has noise.)

 

If you were to leave the lens cap on and take the fastest possible exposure at base ISO (ISO 100), then inspect the pixels in that “black” photo (since you would have guaranteed no light could enter the camera), you’d find the pixel values aren’t actually zeros... there very low values just fractionally above 0.  This is because in order to operate the sensor, it has to be powered up (voltage must be applied) and there’s a minimum charge that can be read out from each pixel as a result.  This is called the “bias” level.  Also, you’d notice that the pixels wont all have the same value.

 

When the camera performs a read-out of the sensor, it collects “read noise”, there is also “thermal noise”, there’s even quantum noise (which can’t be eliminated ... it’s in the nature of the universe).

 

There are many kinds of noise that collect... but in order to not notice the noise you need to collect enough “signal” that the signal (good data) overwhelms the noise so that the noise simply isn’t noticed.

 

 

 

 

Enough on “why” you have noise (you can find loads of technical articles on noise if you want to know more).  Once you have It, you can still do things in post-processing to reduce it.

 

”noise” is basically a pixel that reads a slightly higher value than it’s neighbors.  This really tends to be noticed in dark shadowy areas... and also in smooth non-contrasty areas.  It tends to not be noticed in bright areas and is more difficult to pick out in areas with lots of details (it can get camofauged in the detail).   

 

The process of de-noising involves sampling neighboring pixels and then averaging the colors.  But in areas of an image with high detail, this can result in the image starting to look soft.  BTW, sharpening is the opposite... this involves finding subtle differences in contrast... and amplifying those differences.  Since a “noisy” pixel is already different in contrast, when you “sharpen” an image you will increase the perceived noise.

 

So to deal with this, use tools that let you selectively sharpen only the areas you care about (e.g. eyes for example) and you can selectively de-noise the smooth areas.  

 

There are de-noising tools that will deal with noise by tonal frequency (since noise tends to be stronger in shadow areas).  But you can also build edge-masks so that you avoid de-noising edges that need to remain sharp... then invert the mask to sharpen only those edges without sharpening noise in the flat areas.

 

 

Tim Campbell
5D III, 5D IV, 60Da
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