What Is Crop Factor? How Does It Affect The Photos I Take? Please Help Me! Hi and welcome to Episode 122 of the Photography Explained podcast.
I’m your host Rick, and in each episode I will try to explain one photographic thing to you in plain English in less than 10 minutes (ish) without the irrelevant details. What I tell you is based on my lifetime of photographic experience. And not Google. Sorry, Google was deployed here just to make sure I got my facts right on one thing.
Want me to answer your photography question? Get your thinking caps on, more on this at the end.
Here is the answery bit
Crop factor is a number used to calculate the effective focal length of a camera lens on a cropped sensor or micro four thirds camera, compared to the same focal length on a full frame camera. Photos taken with cropped sensor and micro four thirds cameras are in effect zoomed in, when compared to the same focal length on a full frame camera. Photos taken at the same focal length on cropped sensor and micro four thirds cameras have a narrower field of view, meaning you get less in the photo.
Blimey. This is one of those. Complicated, quite boring, but very important. I will do my best on this one don’t worry.
Let me explain.
I covered camera sensor sizes way back in episode 8, cunningly titled Why Is Camera Sensor Size Important? I know, these self-explanatory titles really do work. If I do say so myself!
So pop back to that episode for more on this. I want to talk here about how the crop factor affects the photos you and I take, and not chapter and verse on sensor sizes.
But a quick recap should help. And I am talking here about conventional, consumer cameras that us normal folk buy here, ok? There are 3 main types of cameras.
- Full frame cameras
- Cropped sensor cameras – aka APS-C cameras, but I hate that term so let’s stick with cropped sensor cameras
- Micro four thirds cameras
Each of these have different sizes of sensors.
To explain this in English let’s take a standard lens on a full frame camera which has a 50mm focal length. This is similar to how we see the world with our own eyes by the way.
A 50mm lens on a cropped sensor camera has an effective focal length of 75-80mm, as cropped sensor cameras have a crop factor of 1.5-1.6.
A 50mm lens on a micro four thirds camera has an effective focal length of 100mm, as micro four thirds cameras have a crop factor of 2.
To get the same 50mm field of view that you get on a full frame camera with a cropped sensor camera you need a focal length of 31-33mm.
And for micro four thirds cameras 25mm.
I know. Why is this so complicated? Like I say if you want to know more about this check out episode 8, and also episode 6, What Are The Different Types Of Camera?
Now I have got that out of the way I will tell you how crop factor affects the photos that you take. That is the subject of this episode after all.
Focal length/ angle of view
This should be easy now. We have 2 crop factors, 1.5-1.6 and 2. Different numbers but doing similar things.
I know this is rather strange, why is 50mm on a micro four thirds camera called the same thing, but not the same as 50mm on a full frame camera? Evolution in photography is probably the culprit here.
But focal length is a major factor in buying camera lenses, so you just need to make sure that you are applying the crop factor correctly when looking at lenses, and make sure that you apply this back to a full frame camera.
And to do this you need to know if you are putting the lens on a full frame, cropped sensor or micro four thirds camera.
I know……
What you get in a photo
OK – we have established that the crop factor affects the effective focal length. I have a Canon 24-105mm lens, which I use on my full frame Canon 6D.
I take a photo using a 50mm focal length. If I then take a photo at 100mm, I have zoomed in, and there is less of the subject matter in the photo.
That photo taken at 100mm on my full frame camera will have the same composition as the same photo being taken at 50mm on my micro four thirds camera.
This is the main difference. A cropped sensor or micro four thirds camera is, in effect, zooming in by the amount of the crop factor.
Yes, you are getting a telephoto effect with a standard lens. And that is why you have to think about this, as if you got say a 24mm lens on a micro four thirds camera you are not getting the field of view that you would get with the same focal length on a full frame camera – no you are getting an effective 48mm focal length. Yes – wide angle becomes standard.
I say effective focal length as there are loads of other factors, but this is the headline news.
Does crop factor affect depth of field?
Yes it does. You get more depth of field with a micro four thirds/ cropped sensor camera than you do with a full frame camera, with all things being equal that is. And the more I looked into this, yes this was the thing that I needed to research, the more I looked into this the more I realised one thing.
I have a full frame camera system, and I also have a micro four thirds camera system. And I have never, ever compared the relative depths of field of the two camera systems. It is only in writing this paragraph that I have even thought about this.
Massive oversimplification alert - there are many other factors here – but - you get more depth of field with a cropped sensor/ micro four thirds camera sensor than you do with a full frame camera sensor. And that is all I need to know.
Anything more to me is irrelevant detail. If you want to know more go for it. I don’t.
Let’s move on. Some related stuff, about sensor size and their effect on photos. Not strictly crop factor stuff I know, but related, and things that I wanted to mention quickly.
File size
- Larger sensor = larger file sizes, in general terms.
Image quality
- Larger sensor = higher image quality, in general terms.
Dynamic range
- Larger sensor = better dynamic range, in general terms.
Low light performance
- Larger sensor = better low light performance, in general terms.
I know that there are millions of variables that can be considered, but these things are generally true, and relevant to what I am talking about here.
The talky bit
Confusing. Understand crop factors and the effect of the numbers and you will be fine.
Crop factor affects focal length, which directly affects the photos that you take, and what you get into a photo. And it also affects the depth of field.
You have to remember the crop factor whenever you are taking photos. It is that simple. 24mm is not 24mm on a cropped sensor camera.
And it does impact on the other areas that I have already mentioned, but we need to remember this. These margins are getting smaller.
How is crop factor calculated? Well it is something to do with the relative size of the sensors, the ratios, the this, that and the other. Oh I don’t know. I do not know and I do not need to know – that will not help me! That is what I call irrelevant detail – none of that here.
And then I wrote a lengthy piece about the merits of full frame, cropped sensor and micro four thirds cameras. And realised that these were not actually related to the question.
But I decided to keep this bit in, well why not, it is related and good stuff too.
I am happy to commit to the fact that, in general terms, you can get higher quality images with a larger sensor than you can with a camera with a smaller sensor. You would expect so wouldn’t you? And if this were not the case there would be no need for full frame cameras.
But advances in technology, both hardware and software, have, closed the gap making this less significant than ever. And this will continue – this is not going to reverse.
So in terms of quality this is less of an issue than it ever was.
And things like dynamic range? With my Olympus EM5 I can deal with that by taking 3/ 4/ 5 photos and letting the camera put them together. Sorted. Job done.
Comparing depth of field and crop factors
I get more depth of field with my Olympus camera than I do with my Canon 6D. I can’t really get my head round that, and it does not affect me as I treat the two completely separately. I never compare the two, and suggest that we just accept this fact and move on ok?
What do I do?
I use a full frame Canon 6D for my architectural, construction and real estate photography work. No crop factor. 17mm is 17mm. Which is what I use.
And I use a micro four thirds Olympus EM5 for my travel photography work. And on that camera 12mm is actually 24mm.
And the different depths of fields? As I said, never thought about it.
The last word – ooh – a new bit that just came into my head – I like this!
Crop factor affects the effective focal length of lenses when used on micro four thirds and cropped sensor cameras. You get less in a photo.
That will do nicely.
Actually I like doing a final summary – I do this straight after writing the rest of it so there is a succinct, accurate summary reflecting the content of the episode. Perfect!
Next episode
Sticking with gear, in Photography Explained Podcast Episode 123 – 9 Reasons Why Camera Sensor Size Matters? And What This Really Means To Us!
I touched on this in this episode, and now I want to revisit this and add to what I said earlier.
Do you want me to answer your question?
Or questions? You’re not limited to one question. My podcast has been created to answer your photography questions, not mine, so please get in touch with your question, and when I answer it I will give you a number of shout outs in that episode, which will exist in podcastland until podcastland is no more. Just head over to photographyexplainedpodcast.com/start ,where you can also find out more about my podcast and do stuff to help me.
This episode was brought to you by another cheese and pickle sandwich. Yes my favourite. And some lovely water, clearly it is a healthy day for me! Sipping my water whilst recording this in my home made soundproofed recording emporium.
OK - I’m done
I’ve been Rick McEvoy, thanks again very much for listening to me and my small but perfectly formed podcast (it says here, yes it really does), and for giving me 10 (ish) minutes of your valuable time. I really do appreciate you sharing part of your day with me, and look forward to hearing from you and answering your questions.
Cheers from me Rick