You need to upgrade your camera when, and only when, you need a camera that can do something in particular that your current camera can not. This is not only true for your camera body but for your lenses and any other accessories that you might need in order to produce a photo you desire.
The specific reasons for upgrading a camera body can be as varied as the different photographs one might wish to take. Here are just a few of them.
- Perhaps you need a faster, more accurate autofocus to capture fast moving subjects more consistently.
- Perhaps you need a camera with more direct controls that allow you to change settings quickly without having to take your eye away from the viewfinder to deal with rapidly changing shooting conditions.
- Perhaps you need a camera that can take bursts at a faster frame rate and for a longer sustained period to maintain coverage through a sequence of events that you wish to record from start to finish.
- Perhaps you need the ability to do some basic in-camera editing and maybe even convert some raw files to jpeg so that you can move time-sensitive pictures to their destination faster.
- Perhaps you need a camera that can weather more harsh conditions without being damaged by them. Or a camera that will hold up to more frequent and heavy usage and last longer.
- Perhaps you wish to produce photographs that can be displayed at larger sizes that require a sensor with more resolution.
- Perhaps you desire shallower Depth-of-Field than is practical with the sensor size of your current camera, even with fast lenses with apertures as wide as f/2, f/1.8, or even f/1.4 and f/1.2. Assuming your lenses are compatible with the larger format, a larger sensor gives the ability for shallower DoF to all of them.
- Perhaps you need a better signal-to-noise ratio for extreme low light situations. Improvements in noise reduction and post processing can only take you so far. And whatever techniques you learn that work well with a lower/older/smaller sensor model will work that much better with a newer/better/larger sensor model.
Until you can articulate exactly what you wish to do photographically that your current body or other gear doesn't allow you to do you don't yet need an upgrade. It is even better if you can articulate exactly how you expect the newer camera will allow you to accomplish what your current camera doesn't. It is fine if you wish to upgrade without needing to and can afford to do so, but don't expect the change in gear to make a marked improvement in your images until you actually need what the newer gear will offer. Because until your skill level and vision demands the improved capability of the newer camera (or lens, or lighting, etc.), you're not going to be able to take advantage of the improved capability the newer gear offers you.
Here's an example of this concept from my last upgrade.
Shooting Scenario: Friday Night Lights
For several years I've shot high school football and marching bands at night under artificial stadium lights that flicker at 120Hz. My normal shooting arrangement was to use an APS-C Canon 7D with a 70-200mm f/2.8 lens and a FF camera with a wider lens (usually either a 24-105mm f/4 IS or 17-40mm). Due to the need to use faster shutter speeds so as to freeze the action with the telephoto lens, coupled with the way focal plane shutters accomplish exposure times shorter than the camera's sync speed, this often resulted in shots that were well focused and timed to capture the exact moment I wished but which were affected by the differences in color and brightness that resulted from the variation in the intensity and color of the lights as the slit between the first and second shutter curtains transited across the image sensor. The faster the shutter speed selected, the narrower the slit between the two curtains, and the more pronounced the effect of the flickering lights would be. One side of the frame could be dark and a brownish looking color and the other side much brighter and a cooler color temperature. Or the entire frame could be dark and brown (when the shutter transit time was centered on the lights at their dimmest) or too bright and much cooler in color (when the shutter transit time was centered on the lights at their peak). Post processing these images was extremely time-intensive and many otherwise good images were unusable due to the problem with flickering lights.
Problem: Dealing with Flickering Stadium Lighting
I pay a little attention to forthcoming product introductions, but I'm far from obsessed by them. For years the word of an impending replacement for the 7D had been coming down the pike. By the time the Canon 7D Mark II was officially announced I had little interest in ever buying another APS-C camera. In order to take advantage of the superior AF system of the FF Canon 5D Mark III, compared to the more inconsistent AF system of the 7D, I had begun to use the 5D3 with my 70-200 and an older 5D2 with the wider lens much of the time when shooting under lights at night. This gave me more consistent AF performance, but did nothing for the problem with flickering lights. I also gave up the "extra reach" of the APS-C camera which is a rather significant consideration when comparing the difference in cost between a 70-200mm f/2.8 and a 300mm f/2.8 lens!
Then I read a review of the newer 7D and one word describing a new feature leap off the screen at me: anti-flicker. Of course the first question I wanted to ask was, "Does it really work?". This was closely followed by my follow-up question: "How good is the new AF system based on the same one in the full frame 1D X and 5D3, but still with the narrower baseline due to the size of the APS-C mirror? After several months of researching those two questions and learning everything I could I decided to acquire a 7D Mark II before the beginning of the next fall's season.
Solution: Canon 7D Mark II with Flicker Reduction
I've been very happy with the upgrade. The single feature for which I purchased the camera has led to measurable improvements. Some of them are related to image quality, while others are related to the efficiency with which I can deliver images. And the AF system in the 7D Mark II is much better than the AF system in my original 7D, although it is still not quite as good as the AF system in my 5D Mark III.
- Because the lights are at their peak when the shutter is released, depending on the particulars of the lighting in a specific venue I can actually shoot anywhere from 1/2 to 2/3 to one full stop faster and still get the same exposure levels I got previously when I set exposure based on the average intensity of the lights rather than their peak. In the same stadiums where I once shot at f/2.8 and 1/500 second, I can now shoot at 1/800 or even 1/1000 second at the same aperture and ISO. Many times this is the difference for what I shoot between freezing the action and having the feet/legs and arms/hands of the athlete blurry with their movement.
- By releasing the shutter when the lights are at their peak in the cycle, every image shot in a burst has the same brightness and color. This allows me to apply the same WB and exposure correction to the vast majority of the raw images in post processing. My work flow is no longer bottlenecked by the need to custom color-correct every image separately.
- The consistency between each frame also means jpeg images generated in-camera are also the same brightness and color and much more likely to be usable straight out of camera (when I set the correct exposure).
- With both raw images and jpegs, the entire frame has a consistent exposure level and color. Players on opposite sides of the frame wearing jerseys for the same team actually look like they are wearing the same color!