Digital on a budget - RAW ramblings

[oldgreygary]

Over the past week I decide to switch over from Jpeg to Raw. I have read a bit about Raw but as with most of this you need to try for yourself and see the results. I am confident that there are folks on this forum who have a lot of Raw usage experience who might be able to comment. Anyway, bearing in mind that the Canon G2 has limited f stop and shutter speed options. e.g. f2 - f8 f-stops.

This is the basic scenario that I used with some ad-hoc one's as well. In Bryan Peterson's excellent book 'Understanding Exposure' he suggested an exercise to see the results of light. Principally this was not worrying too much about the composition but shooting from the same spot but using the four compass points i.e. North, South, East and West. In other words moving 90 degrees on the same spot to take the image. I decided to set the camera to work in aperture priority this was at F8. I also set the exposure adjustment to -1/3. Now I am not sure why, but I think I read somewhere that it is better to slightly underexpose Raw images? I also manually set the camera and took some random shots of other images. I also set the metering to centre weighted.
I am using Rawtherapee as the software to convert the Raw data.

It was when I got the results in Rawtherapee and tried to edit them that the wheels came off and I wasn't totally sure what was going on. As expected the images were underexposed. That seemed to be the problem. I couldn't seem to use the software to produce a good image. It did seem that because of the underexposure, trying to recover from this produced what seem to me anyway a lot of noise and fuzziness. However, when I shot the random shots this was using f-stop F2, F2.8 then the results were better. I guess you could call these 'close-up' shots whereas the f8 shots were more 'landscape' style shots. I guess shallow and long depth of field respectively.

I have to admit that Rawtherapee has a 101 options which doesn't make things easier. But, I don't think I can blame it. As I feel that it is at the point of shooting and my settings that are causing the basic problem. If my explanation is not clear then I will do my best to clarify. Anyway, thats already too much rambling, but if anyone would like to comment then I am very interested to hear your thoughts.

Cheers for now

Gary

[krispix]

Hi Gary,
I don't know Rawtherapee so I can't comment on it, but perhaps it's just a means of converting a RAW image to a JPG or similar.
A RAW image has often been compared to a negative from the old days of film. It is, in fact, all the data captured by the camera. If you record your images in-camera in JPG the camera will collect the data (in RAW) then process it to what it thinks the finished product should be which it then saves as a JPG. The rest of the (unused) data is dumped.
If you record in RAW you must have a RAW editor to enable you to view the image. Adobe's ACR is bundled with Photoshop, but you will often find a RAW editor in the software bundle that came with your camera. But, be warned, a Nikon RAW editor will not work with a Canon RAW file etc.
When you open the RAW file you will have a number of editing options available to you; Colour Balance, Sharpening, and much more. When you've made all the adjustments that you want, save the file as a JPG and continue with more manipulation (healing, cloning, cropping etc.) as normal.
The main advantage with RAW editing is that you never actually change the RAW file regardless of what you do and it can always be retrieved in it's original form to be worked on in a different way.
Hope this helps.

[Donald]

Gary

RawTherapee is good tool. I used it for a while, but I now find that DxO Optics better suits the way I work

..but I think I read somewhere that it is better to slightly underexpose Raw images?

I don't understand that one. If it was written somewhere, I have no idea what the context was of it being said. As far as I'm concerned, get the exposure right. Indeed, the mantra I was taught was 'shoot to the right'; i.e. get the exposure set to get as much of the data over to the right hand side of the histogram as possible. So, instead of under-exposing, that's pushing towards over-exposure.

It did seem that because of the underexposure, trying to recover from this produced what seem to me anyway a lot of noise and fuzziness.

That is exactly what you would expect to get, which is why I don't understand the 'under-expose' idea.

And I'd agree. You can't blame RawTherapee. It's just trying to deal with the data it's given to work with.

[herbert]

Hi Gary,

Have you read the CiC tutorial on raw:
https://www.cambridgeincolour.com/tu...ile-format.htm

It can seem like a lot of hard work to convert a raw file. However this is not true. If you shoot your photo at a good exposure then the raw conversion should be easy. It is when the exposure has problems that more work is required. The advantage in the second case is that you can control the process each step of the way. If you shot the same scene using JPEG then the camera would do the conversion using a best guess for each step. Taking control of the raw to JPEG development is a very useful tool for hard shooting conditions.

After a quick search of the internet I could not find out if your camera can record raw and JPEG at the same time. This would be a useful feature for you. If not then shoot the same scene with raw and then JPEG in quick succession with the same settings. A tripod will be useful. Then try and see if you can get the raw development to match the JPEG. This will give you an idea of the 'standard' development process. It will also validate if your raw images are doomed since your JPEGs act as a baseline.

Regarding under exposing for raw images this is absolutely not true. A good start is to use the same exposure control as you do for JPEG, i.e. zero for most things, +2 for snow white and -2 for dark objects. You are just telling the camera the brightness of the scene. Otherwise it assumes it is a 'normal' grey.

What you must be careful of with a digital camera is over exposing the highlights. If your sensor reaches the maximum number it can store for a pixel the image will be white. Effectively there is no information other than it is not black. This is OK for a tiny area since these form little spots of specular highlights. These are nice dots of brightness you may see as reflections of light in a shiny surface. However large areas of white are not useful. Any manipulation of the image will not know what to do when you adjust tones; Either leave it as white, this looks strange when the rest of the image is darkened, or make it grey, this looks less strange but can ruin a colour photo with a big patch of grey.

Pixels that are white are called "blown out". You want to avoid these. This is why people often say that you should under-expose your image. What they should say is that you should under-expose your image when you have large amounts of highlight detail that you want to keep.

Unfortunately I could not find out if your camera can show a histogram of the pixel values. This will represent how many pixles are at each value from 0-255. Look at these tutorials:

https://www.cambridgeincolour.com/tu...istograms1.htm
https://www.cambridgeincolour.com/tu...istograms2.htm

Note that there is not a perfect histogram for an image. However the histogram will tell you when you are getting close to blowing out your highlights. Then you can under expose if you want to protect them.

The disadvantage of under exposure is that most of your pixels have low intensity. Since most of the noise on the camera is constant a low intensity pixel has relatively more noise than a high intensity pixel. If you make all your images dark (under expose) and then increase the exposure later you will also increase the noise.

Noise is not really evil. Sometimes it helps an image look better. However it always looks worse when there are large smooth areas of tonal change compared with lots of detail. Think of this as a bunch of fine sand on a layer of glass compared to the same sand on a carpet. (This is also why you should use a vacuum cleaner even when the carpet on the floor seems clean.)

Alex

[rambler4466]

Wow, lots of good info in this thread. In that histogram article #1 look closely at the image under "Tones" with the lines and circles pointing to the corresponding parts of the photo. That is very helpful for me. I did give up reading part 2, however. I am not quite ready for all that info! It is easy to get info overload, but it can be rewarding to as you watch your photos improve.

From the back cover of Peterson's books is a link to the website ppsop.com Try taking a course. You will receive a lot of good feedback both from your own images and from the images taken by the other students. (maybe even a novice like me, if you go for April!)

It is great you are getting out and trying those different things with your camera.

I believe it is better to overexpose rather than underexpose. Lightening up an underexposure can lead to a lot of noise when you print. It happened to me.

If you do experiment by printing out the same image say at four different exposures, print them all out on the same page to save a little ink and paper. Read up on color management in the tutorials at this website. Links can be made between monitor and paper with the specific printer you use. You can download free color profiles from the paper makers. (Kodak, Epson, HP, etc.)

[Brev00]

I find it very interesting when people hear general guidelines which then become fixed rules in their own practice. I think there is a time and a place for both overexposing and underexposing an image. More often, I try to get the exposure correct. Even using RAW which allows for great flexibility after the fact, I try to get white balance as close as possible. Who wants to spend a lot of time at the computer rearranging all the data like an overturned jigsaw puzzle? I spend enough time in RAW making enhancements my camera is not able to do so well in the first place (adding blacks and fill, reducing noise, even sharpening). So, while I recommend getting the exposure as close as possible to what you want for the sake of both convenience and the eventual image quality, more important is flexibility. Experiment. You just found out one of the drawbacks of underexposing. But, that does not mean it won't work for you at times. I sometimes purposely underexpose when the light is dropping and I still want to freeze action or if I am shooting into the sun. Lifting the shadows might not result in a perfect image, but, at times, it is better than the alternative.

[Geoff F]

Which version of RT is it, Gary?

I found the latest version 3 to be good, now that it is finally stable, but a little complicated and, unless someone has done it recently, there wasn't any user instructions available. And learning Raw conversion by trial and error is initially a bit of a struggle.

The previous 2.4 version never seemed very 'user friendly' to me, but the latest model appeared more logical.

However, I found that I could download a sort of user manual for the previous 2.4 version and that gave me a good start.

Scarab Labs also produce a Raw converter which is easier to use, but it didn't suit me as well as RT.

And, of course, you could download the Canon DPP converter. Not as comprehensive as RT but possibly a bit easier to begin with; and it comes with plenty of downloadable instructions.

[oldgreygary]

I use PCLinuxOS as my Linux distro. which, I have to say is one of the best I have used. Rawtherapee (V4.04) is one of many 'free' software options available from the repository. I think it can be used on Windows as well (check their website, just google rawtherapee)? There are manuals available on their website as pdf downloads upto version 3. Unfortunately, version 4 is listed as work in progress and not yet available. It is one of the better documented open software manuals that I have seen. I have to say it is very comprehensive in the selections available and in a way for a 'rookie' probably too comprehensive. I guess it is one step at a time. I have to admit to a preference to hard copy manuals and printing .pdf files can knock the stuffing out of ink cartridges very quickly! Will check the Canon DPP sofware I think it is only available for windows?. There is some Raw conversion software specific to the G2 which is available though (this takes it to the other extreme and is basic, to say the least, no Linux version either).

I think that I have somehow got lodged in my mind mis-information about setting underexposure for RAW files. I have quickly perused through some notes I have taken from my reading. The closest I can find is that when shooting in sidelight in North/South direction adjust exposure by +1 for film and -1 for digital. I tend to get books from my local library so I think I need to re-read and make sure my notes are accurate.

I will look at the suggested tutorials on the website. Unfortunately, the Canon G2 doesn't shoot JPEG and RAW at the same time. But, it is still a good idea to try that to have a reference. The G2's LCD is quite small. When you take a shot it displays the image. If you want to review it you have to flick a switch over then you have the ability to look at various options. The histogram is displayed alongside a thumbnail and details of f-stop etc. The thumbnail also blinks if areas are overexposed. The histogram is basic and there aren't any options to change the view but it does give you a feel for whats happening with the image. I have to admit that I still haven't got into the routine of checking after taking an image. Something, I will need to work on.

Thanks for all your replies so far, much appreciated.

Cheers for now

Gary

[Geoff F]

The original G2 Raw converter was the Image Browser Raw Converter, which didn't really offer very much except for White Balance correction. Although it did present a method of avoiding Jpeg compression by converting to Tiff; but only 8 bit Tiff.

The Image Browser software was upgraded into Zoombrowser and Canon DPP.

The old programmes worked for Machintosh and Windows.

I didn't know that RT had reached version 4. A little while ago I struggled with the trial version 3, which kept crashing, then shortly after it became stable I switched to CS5.

And I can't understand any instruction manuals which appear on screen. I have to print them out so that I can keep going through them bit by bit while experimenting. Video tutorials just go straight over my head, and never reach my brain.

But I suppose that is partly a result of coming from a pre digital age - give me a book everytime.

You might find something in this Raw conversion workflow useful; although it isn't for RT

http://www.ronbigelow.com/articles/w...flow_basic.htm

[Dave Humphries]

Hi Gary,

My puzzlement is regarding "As expected the images were underexposed", a mere 1/3 stop is hardly noticeable - if you could see obvious under exposure, I'd venture that the metering and capture was way more than that for some reason.

If you haven't yet got used to checking the histogram after shooting yet, we don't know what was going on - although if you haven't deleted the images, you could check on camera now.

Only other thought is there might be an issue (bug) with RT4.

Can you use www.mediafire.com upload one of troublesome RAWs and I'll check it in ACR and advise. Send me a PM with the mediafire link in.

Cheers,

[Dave Humphries]

Hi Gary,

I got the link and everything worked (mediafire really is simple to use, isn't it?).

Well, the exposure is OK, in ACR (Adobe Camera Raw), if I use "Auto" on it, it only increases exposure by 0.15 stop, although personally I'd push a bit more than that. Clipping starts to set in at +0.8 stops, so the exposure is fine as the Canon set it.

The embedded jpg doesn't look too dim either, so I'd suggest there may be a RAW Therapee 4 problem, perhaps with these older crw files?

Here's what I see; (click and expand to be able to read things)


As we can see from the histogram top right, even with 0.15 (about 1/6th stop) increase, the clouds are still some way off white.

Hope that helps,

[oldgreygary]

Hello Dave,

Thanks for taking the time to look at the image. Mediafire.com is something that I was not aware of and yes, it is very easy to use. I will file that away for future use!

It is good to get a second opinion which is of great value to me. Quite a few of the issues I have are because I don't have a benchmark to measure up against. e.g. Is the exposure ok? Is that what I can expect from the Raw conversion software? What you have shown me is that Rawtherapee is not a million miles away from the results that you are getting.

I think that more of the problem is down to me! Firstly, my familiarity with the software and what to expect from it. Secondly, being confident about the exposure. With regards to the first. I did have a trial version of Adobe Elements and it did seem to me that it was more 'user-friendly'. Also, most tutorials assume that Adobe software is used?! But, I guess you have to keep in mind that any open source software like Rawtherapee is free and people are working hard to get it right in their own time. I also prefer Linux as an operating system!

With exposure I think that is just about getting out and building experience of situations as well as using resources like CIC to get opinions.

Anyway, I feel a lot more confident that I am moving in the right direction.

** addition**

You mentioned embedded jpeg, does that mean that when taking a Raw image it stores a jpeg as well? If so I didn't realise it did that.

I thought I would add a screen dump of what Rawtherapee produces. This is using the default profile that they supply.





Cheers for now

Gary

[oldgreygary]

This is the image after playing around in Rawtherapee and was my best attempt so far! Any further comments are welcome!



Cheers for now

Gary