Advanced Negative Film Inversion
There is a received wisdom on the interwebs that you cannot get positive images from colour negative film in a standardised deterministic manner. Whilst it may be common practice to do inversions from negative film on a one-by-one basis and whilst it is often a perfectly valid approach; there are certainly legitimate times when you may wish for a deterministic approach. This is possible but with one large qualification: You can only obtain this control by locking down all the variables. The inversion of a positive scan of a piece of colour negative film involves some extreme tone curve adjustments which will exaggerate any slight differences in scanner exposure level or colour balance. Also, the algorithms of the software we will be using will be completely thrown off by any clipping in any channel.
ColorPerfect, just like most inversion software, is geared towards doing one-by-one evaluations of given pictures and doing the equivalent of auto levels and auto white balance on the frame. This is a good approach to most single frames but what about the pictures that you took because of the strange mix of light or because of the predominance of a certain shade on the whole scene? What about the panorama that you are trying to stitch together and you need all the sections to receive the same treatment so that they will still match when you stitch them together? For example, if you use the Photomerge feature of Photoshop CS2 it will convert your picture to 8 bit colour depth first. You don’t have enough bits left to do a decent quality inversion after reducing to 8 bits so it is essential that you do the inversion before the stitch if using this software. It also may be that you just want to do your artistic work AFTER the inversion in a different program (I like Lightroom). Whatever your scenario, I’m going to show you how to invert your colour negative scans with CONSISTENCY.
Choose A Suitable Master Frame
The first thing to do is to select a frame that will be a suitable master frame. Since one of the variables we will be locking down is the minimum and maximum brightness range we need a shot with the maximum contrast range. If I have a reel that I shoot with something like my Nikon FE or Kodak Retinette that does not do an auto first advance I will usually have a half frame at the beginning. One that is half picture and half fully exposed leader. If I can get a scan of that that includes a bit of unexposed border I have a guaranteed maximal range. The example you will see here was shot with a DX fisheye lens so it includes a lot of unexposed film (in the area not covered by the DX lens) as well as a portion of direct sun flaring in that gives me very close to a maximal exposure. This is a critical part because colour negative film has a truly phenomenal exposure range and you may be surprised how overexposed a frame can be and still have good image information on it.
Here’s my chosen master frame for this tutorial roll:
The border area is all unexposed film. In the top of the exposed part of the image you can see a black dot which is the sun shining directly in with such force that you can see all around the flare being caused. This may not even be a maximum exposure area but it will be quite close.
We have cropped the holder away from the image and assigned our working profile so now let’s call the ColorPerfect plugin:
OK. I’ve hit the “Intial > Previous” button which has returned my previous artistic adjustments (for example, note that I have adjusted “Gamma” and “Saturation”) and I have selected the correct film type in the drop down menus at the bottom. We can see that the highlight clip range is not zero so we will have to lower the “Black” control to get the whole image into range without clipping. The software has made some automatic adjustments including setting black to the minimum of the three film primary curves and setting the initial “zero” colour balance to the maximum of each primary colour curves being balanced.
Let’s pull down the exposure a little by selecting the “Black” control and pulling down the slider until a bit after we see zero for clipping value:
We can click OK and then use the eyedropper to sample our brightest point.
The goal being to not see 100% or 255 in any one colour channel. If we don’t like the highlight value we simply undo the operation, call ColorPerfect again, click “Intial > Previous” to get our previous settings back and then just raise or lower the “Black” setting as required.
Locking It In
Once we have a good setting for this image that covers the whole range of tones we should be able to use it for any image in the roll without any of those frames clipping. The lower contrast scenes will look low contrast but everything will have the same treatment and there will be a standard “white point” for all of them. In other words, this is the equivalent of setting a fixed white balance and fixed exposure rather than shooting on auto. We still have the freedom to make all of those adjustments artistically later but we have a consistent starting point which is the goal here.
To get there we will have to tell ColorPerfect to “lock in” the automatic adjustments it made for white balance and black point and brightness range. We do this in a panel called “CC Master”. It is accessed by repeatedly clicking the little “+” button in the upper right corner until CC Master appears:
Make sure the three tickboxes are all ticked and then select a “bank” from the popup menu. Here I have chosen a free bank and typed the name “Tutorial” into it. I now click the “Insert” button to insert the current values into that bank and click “OK” to store it.
If you went through the Scanning Colour Negative Film 102 tutorial you may have noticed that after correcting the colour on the spaceman frame we ended up with a sort of purple colour in the brightest highlight. This was unnoticeable once we had brightened the scene up with a Curve adjustment but it illustrates one of the challenges of inverting colour negative film. Each different primary colour has a different gamma (characteristic curve) but ALSO each channel may or may not have a slightly different maxiumum possible density. Because both the curve and the endpoints both affect white balance it can be challenging to get a correct rendering where the colour balance does not change in the low or high tones. Now one of the things that really sets apart the ColorPerfect plugin is their philosophy of colour integrity. When you choose a particular film type the software is locking in the gammas of each primary for that film from known values (either from manufacturer data sheets or measured). This locks down one variable allowing us to address the other. The locking down that we are doing means that we now no longer need something neutral in each frame to get the colour balance right. Something neutral in any of the frames under the same lighting will suffice. Let’s see how this works.
Using The Locked Values
OK. So we locked in the values for our maximum contrast frame. Note that we made no attempt to colour balance this frame. Just ensure that we encompassed the maximum contrast range. We can now use this fixed set of adjustments on any other inversion. Keep in mind that this fixed set of adjustments are probably only valid for this roll. If your scanning and processing are very consistent then it may be valid for other rolls of the same emulsion but if there is any deviation in development or scanning then it may well not be.
To invert a scan to positive using these settings just call ColorPerfect and do the following:
1. Click “Initial > Previous” to reclaim the previous “artistic” adjustments
2. Click the “+” button until the “CC Master” button appears
3. Choose the correct “bank” (in our case “Tutorial”) from the drop down menu
4. Click “Apply” and then “OK”
Here is our original “contrast” frame and also the spaceman frame both done with the same fixed settings:
Consistent Inversion Allows Consistent Post-Processing
So, what have we acheived? These inversions are not as nice as what we achieved before by virtue of our minimal intervention. Notice that these are not “print ready”. They are quite low contrast and there is something wrong with the colour balance. However, they are consistent with each other. And the spaceman has that nice grey suit which makes that particular frame fairly easy to colour correct. Let’s remove the colour cast.
Now, if we were confident of the endpoints we would balance the picture with the grey eyedropper which would alter the gamma curve for each primary channel to achieve grey. If you remember in Scanning Colour Negative Film 102 we used that technique when using the DonzRGB actions to invert the scan via Photoshop actions. We found the endpoints of the colour curves using white and black eyedroppers and then determined the curves by using the grey dropper on something neutral. In this case, however, we are confident of having the right gamma for each channel so we should adjust the endpoints. We will do this with the Levels control:
In this case, I am seeing too much green so I am bringing down the output level for the green channel until the output looks neutral. Here I took it down to 88.1%. Note that the colour now looks right across the image from light to dark:
OK. If these are really consistent then the same adjustment should fix my high contrast frame as well:
OK. Let’s see:
Let’s see, sky, leaves, path, grass, house, bare patch, stem… They do all look about the right “natural” colour but it is still very flat.
Let’s see if we can do the same adjustment to fix the contrast on both:
Hooray! Just as we might expect, the same adjustments are applicable to all shots on this roll taken in the same lighting conditions.
Now, does this mean that the same colour and contrast adjustments would be applicable to a set of indoor shots or nighttime shots taken on the same roll? No. However, if we invert the entire roll using these same locked down ColorPerfect CC Master settings we should be able to work out the correct settings on one image from a sequence and apply them to the rest. In other words, we may need to do something different for contrast and colour balance to get one of our hypothetical indoor shots from this roll correct. But this same correction should then be applicable to any other of the indoor shots from this roll. Anyone used to working in a program like Lightroom or Aperture on a sequence of images from a digital camera with the white balance and exposure settings locked or from a sequence of consistently scanned positive slide film images will be used to working in this way.
One of the things that really draws me to film photography in the first place is that in my opinion the rendering that film gives to the 1% scenes is really superior to what I get from digital capture in those situations. Digital capture really does an excellent excellent job with the 99% of scenes that are completely boring anyway. But unless I’m covering an event who really cares about those shots?
What is a 1% scene? It is when a sudden sand storm turns the whole world a weird yellowy-orange. It is when the first rays of sunshine set the tip of a high mountain ablaze in purple or pink for a half-minute or so at dawn. It is a face in a nightclub lit by three different colours of neon light. Those are the shots I want. Those are the shots that film does better than digital. Those are the shots where auto exposure and auto white balance will just suck all the life out. Those are the shots that lead me to develop a way to do what I have just demonstrated here.
If you have always wanted to work the same way with your colour negative film images — well, now you know how!
Ready to kick it up to the next level? Continue to find out how to bring absolute and accurate colour to your colour negative film scans and leave wishy-washy I-guess-that’s-right colour behind. Read Scanning Colour Negative Film With ICC Profiles