ESFotoClix Blog

The question of whether to shoot in JPG or RAW, and what if any are the advantages of using the RAW format comes up often. The following is not a definitive proof of the benefits of one approach vs. the other, but a sampling of how “getting it right” in camera with JPG shooting works when compared to getting right or almost right in-camera with RAW, then following up with some post-processing tweaks. We will approach this by answering 3 basic questions: (1) How does an out-of-camera (OOC) JPG compare to a JPG resulting from straight-up, none-edited conversion from RAW in post processing; (2) How do minor exposure adjustments to a fairly well-exposed OOC JPG compare to a JPG resulting from the same adjustments on the RAW file; and (3) How do white balance (WB) adjustments on the OOC JPG compare to a JPG resulting from the same adjustments on the RAW file?

Equipment, setup and software used
Images were taken with a Nikon D80 and AF 35-70 f/2.8 lens, using the “Normal” picture mode and WB=Direct sunlight. A tripod was also used to ensure exact framing. Straight conversions to JPG and 16-bit TIF were performed in ViewNX without any adjustments. All exposure and WB adjustments were performed in Paintshop Pro X2, ensuring that the same adjustment was applied to both the OOC JPG and its corresponding TIF version. JPG files resulting from adjusted original files were saved using the same and high JPG quality settings in Paintshop Pro X2.

Comparison of OOC JPG against post-converted RAW-to-JPG version
To answer the first question, here are two sample image pairs. You decide what, if any, are the differences between the OOC JPG and the RAW-to-JPG converted (using ViewNX, in this case) versions. Please note that the OOC JPGs are going to be rotated as I did not want to make any modifications to the camera output (and saving JPG is a lossy process).

OOC JPG	ViewNX JPG

Comparison of exposure-compensated OOC JPG against post-converted RAW-to-TIF version
Now we start by toning down the highlights and adjusting midtones with the Highlight/Midtone/Shadow (HMS) tool, then adding a little contrast with Unsharp Mask (USM) as I prefer doing to some of my images to add pop; and I do this both with the OOC image and the RAW (after 16-bit TIF conversion in ViewNX).

Edited OOC JPG	Edited TIF

Since the exposures we’ve seen were a tad clipped in the highlights, I took a second set of sample pairs, this time with -0.7EV of compensation. Here are the OOC JPGs, prior any adjusments. As you can see, the highlights are in better shape, but the shadows and midtones are under-exposed and dull.

OOC JPG 1	OOC JPG 2

Comparison of WB and exposure-compensated OOC JPG against post-converted RAW-to-TIF version
And here they are after using the HSM tool to bring out the shadows and lighten the midtones a bit, and some USM contrast added in. I would point you in particular to the color/shade transitions in the blue tile for the first sample pair and to the color/shade transitions in the red petals of the second sample pair. See a difference, and if so, is it significant enough for you?

Edited OOC JPG	Edited TIF

Finally, we look at the third question and adjust WB to better resemble the colors in the scene. We do this with the images taken with -0.7EV for the first sample pair, so we also have to add the exposure adjustments discussed above. Again, look for color transitions, and if you are so inclined, go digging through the shadows in pixel-peep mode and see what you find.

OOC JPG	ViewNX TIF

This is a controversial subject and one where expressing any hard conclusions is bound to be unproductive in the face of what is ultimate a matter of preference for many digital photographers. I will say that given these very mild (low contrast) and unchallenging (regarding exposure) images, even the subtle differences I can see are enough for me to continue shooting and enjoying the benefits of the RAW format. I will try and come with additional samples, and if anything more significant than these results comes of it, I will follow-up with a future blog entry.

After making some disparaging remarks about Active D-Lighting (ADL), the data caused me to reconsider. Primarily, I now see I had the wrong expectations.

How I thought ADL worked: I thought ADL would auto-magically compensate for Matrix metering’s (MM) tendency to over-expose. Indeed, in some test cases I saw how ADL applies negative compensation, but not enough to make a difference consistently.

How ADL seems to do best: If you apply negative compensation to MM or otherwise meter to avoid clipped highlights, ADL helps avoid under-exposed shadows through adjustment of the tone curve (or however it does it), effectively pushing out shadow detail and producing a balanced shot.

To elaborate, I assumed that ADL would adjust MM’s tendency to over-expose, much in the same way I sometimes purposefully expose to the right by +0.3 to +0.7EV from what the Spot meter indicates as the centered exposure, then back-off the exposure in ViewNX and apply shadow protection to recover shadow detail. Why I thought ADL would do something similar I can’t really explain, but to move on and learn something new let’s compare some samples of my approach vs. ADL and see which does better. Along the way, we will examine the effect each approach has on noise, and to illustrate the effects of each of the approaches, we will use ISO800.

The first capture uses Matrix metering with ADL=OFF. The bright back-lighting against our dark subject produces the typical Matrix metering clipping in the highlights.

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For the next capture we set ADL to Normal. ADL tames down the highlights a bit, but not enough, and pushes out shadow detail in the vase. Start paying attention at the 100% crop on the right and look at whether noise is becoming more evident there.

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For the next two exposures, we use -0.7EV and -1.0EV respectivealy. Now the highlights are under control, but what is happening in the noise department?

[Click for larger image]
[Click for larger image]

To arrive at this final image we use the first exposure, thankfully captured in RAW, and we apply -0.7EV adjustment in ViewNX and shadow protection = 30. (For another example of this technique, see When Over-exposure happens). Compare the resulting image to the previous 4 samples.

[Click for larger image]

Which adjusted exposure achieves the best noise performance should be self-evident. Which of these achieves a better balance in the overall exposure is probably largely a matter of preference. My perspective is that the last image balances highlights, middle tones and shadows best. I wish ADL or some other algorithm performed similar simple adjustments on the fly in-camera (hint, hint, Nikon).

In response to my Active D-Lighting (ADL) experiments, some have recommended I try ADL with Matrix metering (MM) while applying negative exposure compensation (EC). The suggestion was to use -1 EV, with the idea that this would avoid blown highlights and ADL would compensate through shadow recovery. This makes sense and promises to solve the problem with possible under-exposure that would occur if one were to address Matrix metering’s tendency to over-expose by applying across-the-board negative compensation.

I decided to give this a go with the following five captures using ISO 200, aperture=f/8 in Aperture priority mode.

EC=0 and ADL=off gives an exposure at 1/13sec. An examination of the histogram will show clipping in the reds.
EC=-1EV and ADL=off gives an exposure at 1/25sec. All highlights are well-contained, but the shadows are a bit on the dark side. Time to call ADL to the rescue.
EC=-1EV and ADL=Normal result in an exposure at 1/30sec. The shadows are recovered, and the highlights are well balanced as well.
EC=-1EV and ADL=High yield and exposure of 1/40sec, with subtle further boosting of the shadows while maintaining well-contained highlights.
EC=-1EV and ADL=Extra High also give a 1/40sec exposure, with subtle further boosting of the shadows while maintaining well-contained highlights.

Looks great, right? Well, pay attention to those shutter speeds. Even though there’s no clipping whatsoever with ADL=OFF and -1EV of compensation, ADL=Normal further under-exposes by an additional 0.3EV, and for ADL High & Extra High ADL under-exposes by 0.7EV. We can only imagine what that will do at higher ISO values. Noise will come on like gangbusters. The recommended mitigation would be to stick with lower ISO’s, though this may not always be practical.

Let’s not completely ignore these results, however. If the situation is one where we have plenty of lighting so that keeping the ISO low is possible (i.e., we’re not capturing fast action), and you want to use Matrix metering with negative compensation, ADL may indeed help balance the exposure to avoid under-exposure, especially in shadow areas.

~O~
Addendum: To further illustrate how ADL behaves with under/over-exposure, first we used Spot metering in Manual mode to determine a middle-tone exposure somewhere between 1/25sec and 1/30sec, and bracketed 8 images around this middle-tone value with ADL=off stepping exposure in 1/3 EV increments, from 1/10sec to 1/50sec. Then we switched to MM, turned ADL to High and repeated. Side-by-side comparisons are shown in the following table.

Manual Exposure	Spot, ADL=OFF	MM, ADL=High
ISO 200, f/8, 1/10sec
ISO 200, f/8, 1/13sec
ISO 200, f/8, 1/15sec
ISO 200, f/8, 1/20sec
ISO 200, f/8, 1/25sec
ISO 200, f/8, 1/30sec
ISO 200, f/8, 1/40sec
ISO 200, f/8, 1/50sec

Looking at this last set of samples, it appears ADL does much better when one negatively compensates MM. As previous samples show, when MM over-exposes the highlights by a fair amount (+0.7 to 1.0EV), ADL’s negative compensation may be insufficient to “rescue” the highlights. But if you apply negative compensation or spot-meter in Manual mode to set a middle-tone exposure, then switch back to MM, ADL is in a much better place to adjust the tone curve and achieve a more balanced look to the image. A workable strategy for harsh lighting situations may be:

1. Spot-meter against a middle-tone (approximating middle gray)
2. Manually set exposure to that value (or lock it in a non-Manual mode)
3. Switch to MM and set ADL on (normal or high)
4. Snap away.