What Happens When You Stack Filters? Is it sharp enough? Is the color good enough?
What a brutal winter, eh? But it has been perfect for photography. In Grand Marais, the sun rises over Lake Superior and it sets over Lake Superior, which is what makes it the perfect location for Winter Lake Superior Photography Workshops. And this time of year is when I start my first workshops of the year designed around my changing workshop topics. This year, I’ve changed about 80% of my slideshow and photography workshop teaching topics to what I think is the best I’ve done so far. One of the topics that I teach is stacking filters. What happens when you stack filters? Why you’d want to stack filters? And what are the downsides of stacking filters?
The conventional wisdom comes from years of past photography teachers and writers telling students and reader, respectively, not to stack filters, because the image loses sharpness and creates color casts. The conventional wisdom says don’t stack filters. While this may be true with some lower-end filters, it’s not true with all filters, and — this is a big “and” — the idea that loss of sharpness is the worst thing in photography and color casts are the second worse thing in photography just isn’t true. To be honest with you, I think sharpness is great and natural color is great, but I’m not all that concerned about perfect sharpness or color casts if in trying to obtain them, I have to sacrifice something that is more important to me. For example, if my vision of what I want the final scene to look like is in conflict with perfect sharpness or color casts, then I’m willing to sacrifice the later two to achieve my vision. If we think in terms of chess: my vision is king, sharpness is queen and color casts are the rooks. Sometimes you have to sacrifice a queen or rook to save the king, but if you lose your king and you lose your game.
So, with that in mind lets look at what happens when you stack filters.
Stacking Filters: What happens when you stack filters?
The other week, as an experiment I went out and shot a few images with the most common filters that I stack: split ND grads and ND filters. If you’re not familiar with these types of filters here’s a quick breakdown:
- Split ND grads: a rectangular filter that is split in the middle. The top side is neutral in color and darker and the bottom is completely clear. You put the dark side over the sky, which helps balance the exposure so that you can capture detail in the sky and the ground.
- ND fitlers: a filter with uniform darkness that blocks light from coming into the camera. This lets you using a longer shutter speed than you normally would be able to do. At sunrise and sunset, a 10-stop ND filter can get you out to 4- to 8-minute exposures.
I love ND grads and use them for almost every sunrise and sunset and I love ND filters and use them often. Because I love the look that ND grads give me, I use ND grads with ND filters to stack the effects. With my experiment, I wanted to see:
- What happens when you stack filters?
- What happens to sharpness and color cast?
- And what are the downsides of stacking filters?
Here are the two images. On the left, it’s a 10-stop ND stacked with a 3-stop reverse ND grad. On the right, it’s just a 3-stop reverse ND grad.
This is a pixel-level screenshot of the same composition with different filters. There is no sharpening applied here. White balance is set exactly the same on both shots. Shot at 16mm, which is the widest lens that I own that takes filters. I almost never shoot this wide, but at 16mm we’re going to see the worst of the worst when it comes to filters.
Color Cast: The color cast comes from the 10-stop ND filter. This is Singh-Ray’s 10-stop Mor-Slo and the cast is less than I what I’ve seen from Lee’s Big Stopper and Formatt Hitech’s Pro Stopper.
Sharpness: It looks about the same to me, especially considering that the 10-stop shot is shot at ISO 200 vs ISO 100 and is 222 seconds vs. 8 seconds. If there is any softness in the stacked filter, I think it comes from noise and the long exposure and not the stacked filters.
Color Shift: If you look at the sky, you can see the shift toward magenta in the photo that uses stacked filters. In my experience, this is usually somewhat correctable (if you want) with a white balance mask in the sky. If you’re really picky, then you can correct it even more in Photoshop. I’m not that picky.
Vignetting: The stacked version has much more vignetting. This lens vignettes at 16mm anyway, but the stacking at 16mm makes it much worse. Most of it can be corrected in Lightroom using the “Lens Correction” panel in manual. But, you can remove it completely on the unstacked version and not really remove it completely on the stacked version, so I tend to just go with it. When correcting for this you lose some apparent sharpness in the corners, but that can be brought back with careful sharpening with the masking brush if desired. Typically, it’s just not an issue when you print it.
Below is a quick correct by just changing the white balance using the white balance eyedropper tool in Lightroom. If you spend more time, you can match the color almost exactly. I usually don’t worry about it as long as the color cast looks good to my eye.
Here is an example of the same scene photographed without filters, with a 3-stop ND grad, with a 3-stop ND grad and 10-stop ND filter and then the later adjusted in Lightroom (left to right).
Without stacking the filters, the look in the final shot isn’t doable, so it’s worth it. Remember, don’t fall into a checkmate just because someone says that you can’t sacrifice your queen and rook.
New eBook — Northern Impressions: Favorite Photos from 2013 and the Stories That Go With Them
I have a new eBook out. It collects my favorite photos, one from each month, into an electronic book (pdf). It’s on sale until the 14th for $4.99 (plus tax). After the 14th, it goes up in price to the regular price of $6.99.
Upcoming Photography Workshops
Below are the remaining workshop of 2014. Some are full or close to full, so if you’re interested, you should jump on these now.
Before attending a workshop, you should ask these 10 questions:
- Do you like the photographer’s work?
- How long has he or she been teaching?
- Is there any testimony about how great the workshops are?
- What formal training does the photographer have in both photography and teaching?
- If it’s an outdoor workshop and over 20 minutes away from the hospital does the teacher have wilderness medicine training?
- If it’s an outdoor workshop, does the instructor have guide training and is the instructor able to recognize and avoid risks to keep you safe?
- What is the teacher’s teaching philosophy?
- Is the workshop designed to hit multiple learning styles?
- Does the teacher have intimate knowledge of the area where the workshop is based?
- Does the he or she have the proper permits to use public land?
I think that you’d find that I answer all these questions satisfactory.
- April 5 to 6, 2014 — Neal Smith Wildlife Refuge Photography Workshop in Des Moines, Iowa – Registrations started
- April 25 to 27, 2014 — Spring Waterfall Photography Workshop – Full (Waiting list)
- May 2-4, 2014 – Spring Waterfall Photography Workshop – Nearly Full
- June 13, 2014: Wildflower Photography Workshop at the North House Folk School (Note: register via the North House) – Registration started.
- June 27 to 29, 2014 — Lake Superior Kayak Photography Workshop – Registrations started
- August 20 to 24, 2014 — Northern Night Skies: Night Photography Workshop – 5 day – Registrations started.
- September 24 to 28, 2014 – North Shore Fall Photography Workshop – 5 day – Registrations open.
- October 3 to 5, 2014 – Fall Photography Workshop – 2.5 days – Photography clubs can book this entire workshop.
- October 17 to 19, 2014 — Great Smoky Mountain National Park Fall Photography Workshop – Registrations started.
- October 25-26, 2014 — October Skies: Night Photography Workshop at the North House Folk School (Note: register via the North House)
- November 7 to 9, 2014 — Gales of November Photography Workshop – Registrations started.
The winter in Grand Marais has been awesome and busy! And cold! I’ve lived in the area for 10 years and I don’t remember a year this cold in the last 10, and to me that’s awesome. I love the cold and think that it makes for better photos. The shoreline ice this year has also been great. It’s looking like we’re going to get more winter, but I’m moving into my travel season which I’m excited about, but I just don’t want to leave the area with so many winter photo possibilities. Here are a few photos that I took in January. Click the image to see it larger.