As a tripod blog, we want to establish under what conditions a tripod is even necessary. Conventional wisdom is that sharp images can be obtained in handheld shooting down to roughly 1/focal length in shutter speed. I want to put that to the test using a high resolution camera, the best lenses, and a quantifiable metric for image sharpness. Thus I will be shooting an MTF test chart. Unlike many of the tests done on this site, this doesn’t require any specialized equipment. All you need is to printed piece of paper with a black square on it, and the free software MTFmapper.
In short this MTF test looks at the sharpness of an white to black edge transition. White to black to white would be considered one full ‘cycle’, and so the maximum observable MTF from one pixel to the next is half of one cycle, or 0.5. In practice we never actually observe MTF values that high due to optical imperfections, diffraction, bayer filters, etc. If you want to go down a rabbit hole of MTF testing for handheld images, I will refer you to Jim Kasson’s excellent blog. Here though, suffice it to say that MTF is simply a measure of image sharpness.
For this test I used the Fuji GF 120mm lens as it is the sharpest lens that I have available with image stabilization. I varied the shutter speed using a variable ND filter while keeping the aperture and ISO the same. At each shutter speed, three images were taken and the MTF values from each averaged to give the data point shown. Each image was independently focused by the contrast detection auto focus of the GFX 50S so that any focusing errors could be averaged out. The lens was stopped down to F/5.6, the sharpest aperture for the 120mm and one with relatively little focus shift. The MTF values are given in cycles/pixel and taken from camera generated JPEGs with the sharpness set at minimum (-4 for the GFX 50S). Because the MTF is not taken from raw files, these values should only be taken as relative to each other, and not absolute.
The graph below shows the average MTF recorded at each shutter speed for handheld shots taken with the built in OIS both on (red) and off (blue). Using identical methodology, the black dots show the MTF for images shot on a tripod with OIS off.
The images with OIS on are sharper, not exactly a great shock. We do see the image sharpness of the shots lacking OIS die off pretty rapidly around 1/100s, which is consistent with the general wisdom of using 1/focal length shutter speed while handheld. Note though that we see a small but steady loss of sharpness before that. With OIS on, we are able to consistently achieve reasonably sharp (>0.20 cycles/pixel) images until about 1/8 second shutter. This represents a roughly 4-stop improvement in image sharpness, less than Fuji’s advertised 5 stops.
Surprisingly to me, the images with OIS displayed better sharpness and consistency even above the standard 1/f shutter speed. Even with OIS though, the images didn’t get to quite the same sharpness as those shot off of the tripod. This is reasonable, as we can’t expect the OIS system to perfectly cancel out camera shake. Though, as we will discuss below, this difference in sharpness would be imperceptible in real life photography. I couldn’t shoot fast enough to get perfectly sharp images with this lens, so we will have to choose something with a shorter focal length and easier to hand hold.
Next lets look at the same data but taken with a shorter, lighter lens, the Fuji GF 45mm. This is also an excellent lens and while it displays more significant focus shift, it is well corrected by the camera when using autofocus. This is a smaller and lighter lens than the 120, so I wanted to see if I could match the tripod sharpness while handheld:
At the faster shutter speeds, I saw no difference between the handheld and tripod images. At about 1/100, we start to see a fast and steady decline in the average image sharpness. This is about 1 / 2 x focal length in shutter speed. At 1/ focal length, the images were acceptably generally sharp, but displayed more variance. Dropping below 1/30 I got perfectly sharp images, though one was occasionally usable. Of course, if you have particularly stable hands, your results may be different.
For reference, here is a perfectly sharp image from the 120mm GF:
The numbers are MTFmapper’s annotation for the sharpness of that edge in cycles/pixel. Now for a less sharp image:
While we have lost some of the very fine detail that can be seen in the perfectly sharp image, this is a usable level of sharpness and you can’t really notice any image shake.
This is now noticeably soft but could be acceptable for smaller prints. The point I am trying to make with this images is that the MTF test is very demanding. Images that look sharp when viewed in Lightroom may not be perfectly sharp. So, please don’t send me a message saying “I can get sharp images handheld at much slower shutter speed X” without quantifying your image sharpness. Everyone’s hands are different though, so results will indeed vary. Jim Kasson has done similar tests and achieved similar results.
While not the primary subject of this post, I also tested a the 120mm GF on the tripod with the OIS on:
I see now difference between the images that is statistically significant. Note that the sharpness appears to dip slightly around 1/10. I’m not sure exactly why this is, but I suspect that it is from the variable ND filter causing a slight loss in optical quality as it is rotated. It is also possible there is some slight vibration from the shutter or focusing mechanism that I am not accounting for. If the later were the case though, I would have expected more of a difference between having OIS on and off. Anyways, I still have yet to see any evidence that leaving OIS on while the camera is tripod mounted is harmful.
- At fast enough shutter speeds, perfectly sharp images can be obtained without a tripod.
- Image stabilization helps a lot, but doesn’t perfectly correct for image shake.
- I received roughly 4 stops of benefit from OIS. It may be different for you.
- For handhold use, I would want to use 1 / 2 x focal length to get super sharp images. This applies to all camera formats with similarly sized pixels. Your results may vary depending on how stable your hands are.
These results roughly follow the conventional wisdom for shooting in today’s world of high resolution digital sensors. So, while there aren’t any dramatic conclusions here, it is important data for us to establish and will be a reference point moving forward.