DPC Mentorship - Exposure Part II

Canon EF-S 18-55mm f/3.5-5.6

09/16/2005 07:51:17 PM · #51

JPG straight from camera:

histogram

Level-adjusted to my taste:

levels
histogram

Strong gamma shift for DPC-style drama:

levels
histogram

In that last one, I probably would have gone back and done some additional burning to kill the last fragments of detail on the left, as well, or some color trickery to conceal it, but for this, I'm using only level adjustment.

armelle

Canon EOS-300D Rebel

09/17/2005 11:08:34 AM · #52

Sorry I'm late...

I had a hard time finding a photo with a nice bell curve distribution. This one had a broad bumpy histogram with a main peak pushed on the right side but I was curious how it would look...

Straight from camera.

Cropped and levels using only the black and white droppers. I picked the darkest building shadow and the brightest sun shined snow patch

Cropped and levels using only the arrows. Went from 0-1-255 to 31-0.86-243

09/17/2005 11:23:07 AM · #53

Originally posted by pidge:

SOOTC

Levels

RGB: 0 1.55 200 Red: 54 1.00 161 Green: 62 0.91 154 Blue: 81 1.00 139

It's easy to see Levels made quite a difference here. You've brought out detail that was easy to ignore inthe original. The edited photo has greater contrast and therefore depth and you've made us feel the contour of the hillside. All that's good! You said you weren't happy with it but not why. From my perspective, you may have gone a little too far with the RGB gamma and your white and black points in the red channel, green channel and blue channel are pretty aggressive. I find a light touch tends to give better results. I took a stab at it and ended up with:
RGB: 25/.92/186 R: 23/1/230 G: 5/1/243 B: 8/1/255
Give those a try and see if you think it's better.

09/17/2005 11:32:15 AM · #54

Originally posted by tolovemoon:

Original

Master Output levels 233, 61
Input level 41, 0.88, 209
(383,: 459) R:137, G:98, B:70

My third edited I used auto because that is what I usually use when I upload my photos and edit them. ...
(576, 6) R: 224, G:255, B: 255

For a "single hump in the middel" histogram, Auto often gives good results. I usually bring up the Levels dialog box and click the auto button to do Auto Levels (rather than selecting it from the adjustments menu.) I can then further tweak the settings. I tried it with yours and then reduced the gamma to .92 and was pretty happy with the results. Give it a shot. I have personally not had very good luck adjusting the output levels so I usually leave them alone. Just me.

09/17/2005 12:06:19 PM · #55

Originally posted by Zed Pobre:

JPG straight from camera:

histogram

Level-adjusted to my taste:

levels
histogram

Strong gamma shift for DPC-style drama:

levels
histogram

Zed this is a fine study illustrating what can be accomplished with only Levels. Well done! Your original photo was well exposed but a little dark overall. You first edit brightened it up a bit and emphasized the natural contrast of your scene. Your last edit was more dramatic still. To my personal taste, I like the middle photo best but I understand your editing strategy in the third one and recognize it as work in progress. Nice job on all three, actually!

09/17/2005 12:14:02 PM · #56

Originally posted by armelle:

Straight from camera.

Cropped and levels using only the black and white droppers. I picked the darkest building shadow and the brightest sun shined snow patch

Cropped and levels using only the arrows. Went from 0-1-255 to 31-0.86-243

Armelle, this is terrific! I grew up in the western US where winters were cold (-20), crisp and frequently sunny. You have captured the quality of light I associate with low-in-the-sky winter sunshine beautifully. I am happy you tried setting the white point and black point from white and black areas of the photo. When a photo has some good blacks and whites in it, this often works very well. I like how this changed the color of the pueblos slightly. The color looks a bit more saturated to me, an improvement over the original. And the quality of light in the shadows improved. Nice job!

Message edited by author 2005-09-17 12:16:21.

09/17/2005 12:46:39 PM · #57

Okay, you all did a nice job on our last exercise. Time to move on ... to Brightness/Contrast.

Brightness/Contrast is another tool you can use to alter the histogram of your photo and therefore it's exposure. In Levels, you had 3 controls: White Point, Black Point and Gamma. In Brightness/Contrast you have only two. What's missing? The gamma adjustment. And with the 2 there are, we need to back into exposure correction.

By changing the Brightness control, you can move the whole histogram to the right or the left. Move the slider to the left and the histogram shifts toward the dark edge. Move it to the right and it shifts the whole histogram towards the light edge. If you shift it too much you will get clipping, so be careful.

By changing the Brightness control you are stretching our or narrowing the histogram. If you stretch it your photo will have a wider dynamic range (greater contrast), but again watch out for clipping. If you narrow it, your pixels will be concentrated in mid-tones (lesser contrast).

If this seems a bit obscure, don't worry. Grab a photo with a "humpy in the middle" histogram (use the SOOTC photo from the last exeercise if you like) and play with Brightness/Contrast controls. Notice what's happening to the histogram as you slide each control. Notice what's happening to the photo with preview turned on.

As an editing strategy, I try to slide the hump toward the center with Brightness to correct overall over or under exposure. And I try to broaden the histogram until I get just a little clipping on each end to improve tonal range and contrast.

Exercise 4
4.a Choose a SOOTC photo (you can use the one from the last ecercise or choose a new one) with a "humpy in the middle" histogram and edit it using only Brightness/Contrast. Post the original and edited photos here. And tell us the Brightness and the Contrast numbers you ended up with.
4.b I believe Brightness/Contrast is inferior to levels for several reasons. Think about it and tell me, in your post, at least 2 reasons why it might be inferior to Levels. And tell me when you might use it anyway instead of levels.
Deadline: EOD Friday

Message edited by author 2005-09-17 12:56:13.

Balko

Canon EOS-400D Rebel XTi

09/17/2005 07:52:47 PM · #58

-26 / +36

While not very humpy, this one was a good example for B/C, which I usually do not like to use (preferring Levels). Levels gives me more control over dark & light without washing out the whole image.

09/17/2005 08:02:05 PM · #59

Originally posted by papagei:

-26 / +36

For not liking B/C much, you sure did a nice job in this photo with it. Well done!

Think about it ... when would you use B/C instead of Levels you prefere?

Balko

Canon EOS-400D Rebel XTi

09/17/2005 08:26:14 PM · #60

Why thank you :)
Since I go right to Levels when I edit, I rarely, if ever, use B/C. I noticed that it saturates colors very nicely, so perhaps that can be used instead of Hue/Sat at times. It seems B/C is good for darkening darks, but I cannot see using it before, or instead of, Levels. I'd have to use it a bit to see its worthiness :)

I used levels on this image: 35 / 0.72 / 230

I still like Levels better :)

Message edited by author 2005-09-17 20:30:19.

Tallbloke

Canon EOS-350D Rebel XT

Nikon AF Nikkor 50mm f/1.8D

09/19/2005 02:37:52 PM · #61

Here's one from a wee while ago, taken on the way back from Oban as we were driving into a big rain shower. I chose this because it had a decent histogram, bumpy in the middle but not much at either end.

Edited using Brightness Contrast only

The biggest pain using B&C was that I couldn't see the histogram while adjusting the levels so my desire to spread out the histogram neatly to the edges was complete guesswork. Another limitation is that the linear black to white balance stays the same relatively, i.e. you cant boost or drop the middle or the upper or lower greys if needed. Hope that makes sense, I know what I mean anyway ;-)

Steve

edit: Added post B&C edit Histogram

Message edited by author 2005-09-19 16:00:23.

David.C

09/20/2005 05:46:29 AM · #62

Originally posted by Tallbloke:

... The biggest pain using B&C was that I couldn't see the histogram while adjusting the levels so my desire to spread out the histogram neatly to the edges was complete guesswork. ...

Steve

In photoshop a histogram is always available, just open the histogram pallet (Window/Histogram) -- it will update in real time as you make other adjustments, but it may have a bit of a lag at times.

David

Message edited by author 2005-09-20 06:56:13.

Tallbloke

Canon EOS-350D Rebel XT

09/20/2005 08:50:00 AM · #63

Doh!

Thanks, I hadn't realised that

(feeling stupid now)

Steve

Canon EF-S 18-55mm f/3.5-5.6

09/22/2005 10:55:02 AM · #64

Originally posted by Tallbloke:

Edited using Brightness Contrast only

Nice job with this Steve. To my eye, the adjustment made a positive impact, increasing the drama of the photo. Thanks for posting your histograms before and after. They really illustrate well what's going on. You've got a little clipping going on in both the blacks and the whites (you can tell by the telltale spike at each end). Remember, you can alt-click on the sliders to see what's clipped. In this case it's not so significant to cause any trouble. You are right of course, that you can't boost the mid-tones with B&W adjustments, just make a linear stretching of the the histogram. Sometimes that's all that's needed, other times, it's a real limitation. David's already given you the tip about opening the histogram

Message edited by author 2005-09-22 10:58:09.

armelle

Canon EOS-300D Rebel

09/24/2005 11:08:21 AM · #65

Late as usual :)

This image had two broad bump (not 100% sure what that means compared to one middle bump in terms of image quality?)... but anyway, I increased the brightness +9 and increased the contrast even more +19. The histogram got flatter and broader but without spikes at the end. Levels seems better since it has more parameters to play with... Not sure when B/C is better? I often use it after playing with levels to make additional adjustments.. I'll try playing with the same image doing both methods to see if levels can do it all

PS: Not sure how to post the actual histograms here but I'm so glad I know where to find them in PS now, I thought it was only available with levels! Thanks!!

Message edited by author 2005-09-24 11:14:07.

09/26/2005 06:39:48 PM · #66

Originally posted by armelle:

These 2 photos illustrate the improvement possible with a "light touch" on the controls of adjustment tools. Besides popping the photo, you also increased the sharpness while you increased the contrast. Good job.

All: I had posed a question about why you might use B/C instead of levels. Among the answers you gave were the two I was looking for. The first has to do with sharpening. B/C can be used as a sharpening tool because it increases the contrast of adjacent pixels which the eye percieves as sharpening the image. The second answer relates to a post levels procesing step when just a smidge of B/C will pop the photo a bit.

Good job all.

09/30/2005 01:44:20 AM · #67

As Digital Quixote has by now informed you privately, I'll be picking up for him for a short time while he's away and covering the RAW workflow.

The very first thing to cover is exactly how one works with RAW files. I'm using Adobe Photoshop CS2, which comes with Adobe Camera Raw 3, and as such my views are likely to be a bit slanted around this particular tool, but there are a number of other tools you could possibly end up using to either import RAW files directly into Photoshop, or convert first to a 16-bit TIFF, and then subsequently edit in Photoshop.

If you're not using a recent version of Photoshop, the cheapest way to convert from RAW is to use either the free UFRaw tool, or if you are a Nikon or Canon owner, to use the Canon Digital Photo Professional or Nikon Capture software that was included with the camera.

In addition to these, there are a number of commercial RAW packages out there. Among the ones I have seen recommended are Bibble (which other than UFRaw is the only converter I know of that works in Linux), Capture One, and Rawshooter Essentials.

Before we get started, I'd like to get a quick heads up on which software package you intend to use. Take a moment to make sure you can either import from your RAW file directly to Photoshop or save to a 16-bit image, and then post which software you used to do so.

Since this is a very simple thing, I'd like to set the deadline on this to Sunday, and I'll post the first actual lesson on RAW on Monday.

09/30/2005 07:29:24 PM · #68

I want to welcome Ward Robinson (warddp) to our merry band. He will be joining the mentor group effective immediately. Welcome Ward! And remember, there's homework here and we expect you to participate actively!

thehitter

10/01/2005 01:04:45 AM · #69

hi
thanks for letting me in
i am using cs, but will be upgrading to cs2 for all RAW processing. 16 bit is no problem.

10/01/2005 03:50:46 AM · #70

There's not that much difference between the raw import from CS1 to CS2 (just some automatic detections really changed and some fine-tuning of color values that I don't intend to touch on), so that should be an easy migration for you.

sheapod

Tamron SP AF 28-75mm f/2.8 XR Di for Canon

10/02/2005 12:28:57 AM · #71

I use Digital Photo Professional for RAW files. I have to convert them before opening in PS 7

Zed, thanks for taking over while Chuck is on vacation. I know so little about RAW that I barely even understand the benefits. Except for adjusting the WB -- that has saved me more than once. :-D I look forward to learning from you.

Ward, welcome to the group. It's a lot of fun and we learn alot.

- Laura

10/02/2005 01:21:08 AM · #72

Sheapod, just to be sure, when you convert for Photoshop, you're converting to a 16-bit TIFF file, and not straight to JPG, correct?

sheapod