Canon DPP Histogram interpretation

[Swatcher]

I've been slowly getting my head around histograms, thanks in no small part to the contributors of this board. I now monitor this as a matter of course, pushing my exposures as far to the right as I can. The results have been encouraging with fewer duffs.

However, the DPP RAW histogram is still puzzling. I refer to the scale along the bottom, which goes from -11 to +4 with a double line at 0. The documentation doesn't explain what (I think) I need to know and I've given up on Canon support.

So, why is the scale like this, what is the significance of the 0 point and can I ignore it as i have been doing so far? I wouldn't ask but several snow shots, when exposed right look so burnt out I wonder if I'm missing something.

 

[goinggreynow]

Swatcher
Have you by any chance been able to obtain an answer to your original question?
I was about to ask a similar question myself but then spotted your original post from January. I appreciate that no replies have been received, so decided there was little point in me asking exactly the same thing again.
Regards

 

[tdodd]

I'm a firm believer in using histograms when shooting and to assist in final tweaking when editing. However, I have to say that the raw histogram in DPP is absolute pants. The RGB histogram is more revealing but not much help when you are trying to use the raw tab for adjustments.

I think the best thing to do is to use the raw histogram as nothing more than a gerneral indication of how your tonal distribution looks, but if you enable highlight and shadow clipping warnings you will be able to see which parts of the image, if any, are at clipping point. You can use the controls within the raw histogram to set your highlight and shadow clipping points, and the alerts will let you know when you've got there, which is more than the histogram will.

I gave up on using DPP for editing a long time ago and now use Lightroom exclusively. I find Lightroom's histogram to be well sorted and it tells me all I need to know.

Here's how Lightroom renders the histogram for the same image. There is no doubt about how the data relates to the clipping points., and there are clipping alerts as well.

 

[Swatcher]

I was just about to say no I haven't, goinggreynow, but it seems I/we have after all. Thanks, Tim. I am also on Lightroom now and think it's vastly superior to DPP. Nice of the histogram to light up the bit you're about to adjust and I'm very grateful for the straightener! If you get tempted to give it a go, goinggreynow, be aware that it won't pick up any of your DPP settings so you have to start again from scratch. Unless Tim knows any different...?

Cheers all,
Swatcher

 

[petersmart]

I've been slowly getting my head around histograms, thanks in no small part to the contributors of this board. I now monitor this as a matter of course, pushing my exposures as far to the right as I can. The results have been encouraging with fewer duffs.

However, the DPP RAW histogram is still puzzling. I refer to the scale along the bottom, which goes from -11 to +4 with a double line at 0. The documentation doesn't explain what (I think) I need to know and I've given up on Canon support.

So, why is the scale like this, what is the significance of the 0 point and can I ignore it as i have been doing so far? I wouldn't ask but several snow shots, when exposed right look so burnt out I wonder if I'm missing something.

I always use the histogram on the camera and also set the scene to blink to warn of burnt out highlights.

If I get such a warning I just adjust the exposure until the highlights are not burnt out.

Using these 2 you can get better shots.

 

[tdodd]

be aware that it won't pick up any of your DPP settings so you have to start again from scratch. Unless Tim knows any different...?

Cheers all,
Swatcher

Changes made to a file in DPP will be completely ignored by Lightroom. In fact, Lightroom ignores all the picture parameter settings, such as picture style, recorded when you took the shot. Lightroom will make its own interpretation of how to render the files. Actually, there is one exception to what I've just said. If you use HTP, which forces a 1 stop underexposure of the raw capture, Lightroom will see that you had HTP enabled and will brighten the image automatically to compensate. I don't recommend that raw shooters use HTP.

Back to the DPP histogram for a moment.... The following is my understanding of things, and probably close enough to truth to be good enough, but it might not be 100% factual....

In DPP, the 0 point in the histogram should correspond with "middle grey" or the tone you would get from the camera if you shot a plain subject - sheet of white paper - with exposure compensation set to 0, or with 0 on the meter if shooting manual. The +4 part of the histogram represents the point where data is clipped beyond the possibility of recovery, even in raw. Ideally your capture should probably not go (much) above +3, but the histogram makes it so hard to see where the right hand tip is that it is near useless.

The left hand side of the histogram refers to the shadow areas and should have a -10 limit when showing files from a 14 bit camera and be constrained to -8 when processing files from a 12 bit camera. Thus, in total, the histogram represents the bit range the camera is theoretically able to record. The "problem" with the left hand side is knowing really where it ends, because at different ISOs you will get different amounts of noise, decreasing dynamic range by limiting the detail that remains usable above the shadow noise. Basically I think the left hand side has no real use at all, other than to adjust the black point for the image by dragging the left edge of the histogram inwards until your blacks (should there be any) are truly black.

There is a small commentary on the DPP raw histogram in the DPP tutorials here - http://www.usa.canon.com/dlc/controller?act=GetArticleAct&articleID=1228. It doesn't add anything to what I've said, but might be useful to watch, in case there is something else to be learned. The tutorial is for V3.2, but many of the concepts will still apply in V3.8.

 

[goinggreynow]

Tim, very many thanks for taking the time & trouble to explain in such detail. I guess I'm beginning to realise I don't really understand histograms as much as I thought I did - or perhaps it's a question of just about understanding what I'm looking at but being confused about how to correct things!!
I am also coming to the conclusion that my "work-flow" is all over the place at the moment and I really do need to get my head around what I need to be doing with my RAW files and stick to a rough framework. At the moment I use DPP for my RAW files (changing exposure, picture style, temp & the other sliders, including sharpness); I then sometimes move to the RGB tab to adjust tone curves (but not always!).
It's at this point I often just convert to JPEG for printing ad then start wondering if I really should have converted to TIFF and then open the image in Elements (version 7) to adjust levels, etc!!
As you can see, I'm in a bit of a quandary.
Any words of wisdom would be appreciated.

 

[petersmart]

Well I have a fairly simple workflow.

I have a "template" folder with subfolders in for all conversions and work done on a particular day or shoot.

For instance one folder might be called "Macros - 04 Dec 2009" which is self explanatory.

I download my RAW files to my PC then I burn the RAW files to a DVD.

Then view the RAW files using Fast Picture Viewer and put selected ones into the RAW folder in one of my folder templates.

Then:

1. Batch convert the RAW files into TIFF files using DPP and put them into the TIFF file folder.

2.Use Neat Image to reduce noise in the TIFF files in various stages and put each stage into their own folders.

3. Convert the final NR stage into Small Jpegs resized to 1100px on the longest size which I can view in my browser at a reasonable size - these small Jpegs also have their own folder.

3.Select the pics to use then make a seperate folder for each one and edit the TIFF files using my editing software.

4. Put the final finished pics into a "Finished" folder.

In this way I know exactly what I'm doing and don't lose track of any pictures.

 

[tdodd]

My advice would be to get as much as you can right in the camera and to leave yourself as little as possible to do as far as editing is concerned. Since I shoot raw, the only thing I am really lazy about setting up before clicking is white balance. I usually leave that set to Daylight and then only make adjustments if the aesthetics demand it. Then again, I mostly shoot in daylight, so that's not much of a chore.

I always strive for good exposures, either "correct" or exposed to the right to maximise image detail and minimise noise. Accurate focus, steady shooting and good composition in camera are all big pluses. Sharpening in post can do wonders to make a good photo pop, but it is not the solution to fixing an image that was basically OOF or blurry to begin with, so good shooting technique counts.

If you are after wildlife then getting close to your subject and filling the frame is much better than cropping an image mercilessly, so put in the effort to fill your frame. Your shots will benefit in terms of detail, sharpness and noise, if you can do that.

So, with all that said, if I was to use DPP for editing, as I used to before Lightroom came along, my workflow would be along the lines of....

1. Download images to a "download" folder;
2. Since I always shoot with Neutral picture style I would globally change the picture style to Standard;
3. Since I always shoot with sharpening at 0 I would globally change the sharpening to 3, as my default.
4. If the lighting conditions were constant and Daylight WB wasn't quite hitting the spot I would globally tweak WB to get the look I want;
5. I would quickly run through the images to dump the duffers - blurry, OOF, poorly composed, no eye contact, duplicates etc.;
6. Now I'd run through the remaining shots individually and adjust black and white points and possibly exposure (bearing in mind I often ETTR) and that would probably complete my adjustments as far as overall appearance is concerned.
7. I'd crop, if necessary, to fine tune composition. As most of my images are destined for display on my HDTV I will endeavour to crop them to a 16:9 format if I can get away with it. Otherwise I'll leave them as 3:2 and just tighten the composition if necessary.
8. Then I will batch convert and resize the images to fit into my 1920x1080 display dimensions as JPEG files with quality = 7. The converted files go into a separate folder for processed files.
9. Finally the downloaded and processed files are moved into a folder structure based on YYYY, MM, Subject/Occasion, with one tree for Original files and a matching tree for Processed files.

Here's my folder structure....

So, if I did everything right in camera my only "edits" would be to change the picture style and sharpening, and then only because I choose to shoot with Neutral style and no sharpening, for a better histogram in the camera. Now that I use Lightroom I find that with a well shot image I can go straight from raw to JPEG with no edits at all, or perhaps the most minor of tweaks simply to fine tune black and white points.

Of course, there are occasions when far more aggressive or elaborate editing is necessary, or even desireable, but I prefer to keep my editing to the minimum, if I can. I much prefer the idea of becoming a better skilled photographer than a better skilled image editor.

 

[tdodd]

I was just about to say no I haven't, goinggreynow, but it seems I/we have after all. Thanks, Tim. I am also on Lightroom now and think it's vastly superior to DPP. Nice of the histogram to light up the bit you're about to adjust and I'm very grateful for the straightener! If you get tempted to give it a go, goinggreynow, be aware that it won't pick up any of your DPP settings so you have to start again from scratch. Unless Tim knows any different...?

Cheers all,
Swatcher

DPP 3.8 now includes a "straightener"....

 

[Swatcher]

Wow, this thread has really taken off. Hear, hear to all this. Just a couple of comments to add...

When burning to DVD do two. Murphy's Law seems to apply to computers more than anywhere else! Having done this, when working with RAW in DPP I felt it was enough to save changes as VRD files and the various crops in text files. And don't forget to keep your DVD and daily backups where the burglars won't think of looking!

I too got to the point where I was saving out to an intermediate TIFF as the only means to store a tweaked RAW in uncompressed form which could then be used to produce JPEGs of various sizes. Didn't like doing it because RAW is 12/14-bit (can't remember which I'm on offhand) and TIFFs are 8/16. 8-bits would mean you lose data but 16-bits are huge and the conversion from 12/14 feels like an extrapolation too far, which could introduce artefacts. If people are finding that LR gets round this then that's another reason for having it, I think.

Tim's remarks on the DPP histogram answers my original question. I had begun to suspect that it was important as well-exposed shots - at least on the camera screen - were often showing plenty of activity around here. I never found that adjusting the upper and lower limits was as effective as leaving them alone and doing it on the RGB tab.

As I write I discover from Tim that DPP is now at 3.8 and has a straightener. Sorry, Canon, too late, your s/w should be better in the first place and so should your technical support!

What's the bird, Tim? You caught it really well.

Cheers,
Swatcher

 

[tdodd]

What's the bird, Tim? You caught it really well.

Cheers,
Swatcher

I'm not sure, since I'm not a twitcher, just a photographer. I think it might be either a gyr falcon or a saker falcon. Here's a larger version, processed in DPP with my standard tweaks - WB (= 6000K for this shot), picture style = Standard and sharpening = 3. I've then made a 33% crop for posting here....

If anyone knows what it is, please feel free to chime in.

 

[Swatcher]

Definitely a falcon and from my books looks more like a Saker than a Gyr, going by the vague moustache. I also seem to remember hearing that they are a popular bird with falconers.

 

[goinggreynow]

TIM - thanks again for your post including file structure. Hopefully a final question - when you outline suggested work-flow in DPP, point 6 was to adjust black & white points. If you were in DPP would you do this on the RAW tab or the RGB tab?
SWATCHER - many thanks. Just to be clear, are you saying that I'm potentially losing (final picture) quality by outputting from DPP to TIFF first, then applying other changes in Elements? Sorry if this is a fairly basic question to ask!
Do you think that I really should just be concentrating on either DPP or Elements and not trying to use both in tandem?

 

[tdodd]

Although I've now switched to Lightroom, if I was still using DPP I would use the raw tab almost exclusively for adjustments, ignoring the RGB tab completely. I might sneak over to the NR tab, just occasionally, to back off the default NR if I thought I could improve sharpness without making noise too intrusive.

There's nothing inherently wrong with using the RGB tab, especially if you need to make more intricate "curve" adjustments to your photos, but most advice I've seen says to do your adjustments in the raw tab if there are controls there that do what you need. If you make similar adjustments (e.g. sharpening) in both tabs then the effect is additive. Of course, there are no hard and fast rules. My philosophy is to keep things simple and try to be minimalist in my adjustments. That's why I don't personally bother with Photoshop. Too much learning curve for my tastes. I also don't like the idea of creating an intermediate file (TIFF, JPEG or PSD) and then having to work on that separately. Too much clutter and faffing for my tastes. Either you work on your raw file or you don't. I like a raw file in and a finished JPEG out the back end, nothing else in between.

Of course, everyone has their own preferences so do what works best for you.

 

[Swatcher]

goinggreynow, being quite new to digital photography and RAW processing, it is with some relief that I find myself in agreement with Tim. Get the basics right and do as little tweaking as possible at the most rudimentary level so that these adjustments are carried through. The RGB curve gives you much more control, I find, so if you need to adjust here to get the basic picture right then I would do it. As far as sharpening goes, though, I was involved in another thread on this subject where the opinion was to leave sharpening until the final stage, immediately prior to printing/publishing. Have a read, the sharpening bit starts at the bottom of the page:

http://www.talkphotography.co.uk/forums/showthread.php?t=178994&page=2

TIFFs: Before getting into DSLRs (I used to have a film camera) I spent years doing audio and have been struck by the similarities between that and this. Bit-conversion was something you avoided like the plague and there were always debates about how many to use when recording as converting could very easily introduce calculation "errors", due to the way computers handle binary data, which is what we're all playing with, ultimately. In case you want me to explain this a little better...

Using binary means that doubling and halving are easy, just as multiplying/dividing by 10 is for us. So converting from 16 down to 8 bit should be fine (except of course you will lose detail) but even here, going in the opposite direction means that the s/w has to guess at the intermediate point. As a decimal analogy, where is the mid-point between 1 and 2? It depends on the contour of the curve. The actual mid-point may be 1.5 or 1.6, which would be no problem, but what if it was a third? Decimal can't handle that and similar problems arise with binary numbers so you will end up with an approximation. This is where the artefacts creep in. It may not sound like much but our senses are much more, well, sensitive, that we are often given to believe. Experts in the field can point these out but most people can't, but that doesn't mean they don't hear/see it. In audio you might hear these artefacts as a slightly "clangy" ambience for example.

Computers being computers (and people being people) I don't feel safe in assuming this doesn't happen to the eye too but I must admit I don't trust mine enough yet to know first-hand and so I offer the pov to attract comment as much as to flag something up. But I would be very wary of doing it. Having said that, I didn't find that DPP offered enough to avoid needing an intermediate stage and TIFF was the only uncompressed option available but when I found out that my camera was working in 12/14-bit (can't remember which) I thought I needed to look for a better option. What is the point of spending hours tweaking colours to "perfection" on an expensive monitor only to have the computer screw it up for you because it can't handle the sums properly?

Hope this makes sense and, as I say, invites some comment from the field.

Re Elements, I don't know it but I imagine it won't be able to read DPP adjustments either, not being Canon, so I suppose you'd need the intermediate stage. Photoshop has some basic RAW adjustments, does Elements? If not, can you incorporate Adobe Camera RAW? If so I'd be tempted to see if it is adequate but I don't feel qualified to offer much advice in this area.

Regards,
Swatcher