More F number fun.

So here we are on a sunny day. The camera is set to ISO 200. Why not 50 ? Why not 100 ? Well, you can and you'll be fine too. Personally I like to use highlight priority when taking photos and on the model camera I use, this function will only work from ISO 200 onwards. But pretty much all cameras are noise free at ISO 200 now so off we go ! F1.2 and 1/3200th - no problem ! More than enough shutter speed for even the fastest moving subjects. Canon 85mm F1.2 ii USM L lens used.





At F1.4 now and again the shutter speed is much higher than it'd ever need to be. But that's only 1 part of it. It's not just about the shutter speed. It's about the amount of subject isolation and background blur on these F1.2 and F1.4 lenses and as you can see, the subject is completely isolated from its background. These are the main advantages of lenses with very low F numbers : Amazing shutter speeds and bokeh ( background / foreground blur ). Canon 85mm F1.2 ii USM L lens used.




Here at F1.8 you can see that although the subject is still completely isolated and that even with the much higher than needed shutter speeds for both non moving and moving subjects, the shutter speed has still significantly dropped from F1.2 in the same light. It was previously 1/3200th of a second and is now 1/1250th - a huge difference in shutter speeds so although on a nice sunny day it really isnt going to be a problem but for low light photography the difference between F1.8 and F1.2 is going to be the difference between low and high ISO images as that extra 1/1950th of shutter speed proves how being able to get so much extra light can really help to get a usable shutter speed in a low light situations, unlike when you are limited to higher F numbers - F1.2 is very useful sometimes ! Canon 85mm F1.2 ii USM L lens used.




Moving up to F2 you can not only see how much the shutter speed has changed, but also now how the background blur has lessened. Of course not every photograph will need to have an out of focus background and foreground and the advantage of increasing the F number is that more details will be visible in objects and generally everything in the image will appear sharper than at lower F numbers. Even at F2 though there is still plenty of background blur and subject isolation and as much as the shutter speed has decreased, it is still perfectly usable for non moving and moving subjects and in this light it's still well above the 1/640th limit for an 85mm lens to use handheld for fast moving / static subjects. Canon 85mm F1.2 ii USM L lens used.


The sun went behind the clouds but that's fine, we can use this. Just set your white balance to " Cloudy ". First of all you'll notice the shutter speed has halved. The cloud is responsible for this. Cameras love light.1/500th at F2.8 where at F2 it was 1/1000th. Yes we're using a different lens now with a different sized front element which would give different light gathering capabilities BUT noting how on the same 85mm lens the huge drop in shutter speeds from .8 of an F stop from F1.2 ( 1/3200th second ) to F2 ( 1/1000th ) it seems that the rule is generally consistent. Also now using a zoom lens, the effect of the F number is going to vary depending on what your zoom is set to. It will be more isolated the closer you are to the subject and the longer your zoom. Here at F2.8 zoomed to 52mm the background is much more in focus than before. 1/500th means if you wanted to take a moving subject at F2.8 in this light you would need to increase your ISO to allow you to get the 1/640th+ needed ( or wait for the sun to come out again ! ). Canon 24-70mm F2.8 USM L lens used.


And there comes the sun ! Dont forget to set your white balance back to " Sunny " !!! Shutter speed returns to 1/1000th meaning we can now take photographs of non moving and moving subjects without having to increase the ISO. Also I've increased my zoom to 62mm out of the 70mm available. Small as the difference is, the F2.8 has made the background blur more noticable at 62mm, F2.8 than at 52mm F2.8 using the same focal point. At this distance, not close to a subject the background blur is always going to be less noticeable. If I was very close to the focal point ( the green leafs on the right ) at 70mm F2.8 then the background would melt away to nothing and almost give them same effect as the F1.2 photo ( which was taken from the same distance at 85mm ! ) So once again, the closer / more zoomed in on your subject you are, the more obvious the background blur effect is going to be and the more zoomed out you are, even at low F numbers, the blur / isolation effect is always going to be vastly reduced. So if you want things in focus but still want those low F number shutter speeds, this is always a useful solution. Canon 24-70mm F2.8 USM L lens used.



If you dont own a lens with a low F number, it's alright. Dont panic ! As you can see here, even at F5.6 on a nice sunny day at ISO 200 you're still going to be able to take nice scenic photos of non moving subjects at the recommended 1/125th shutter speed. Cranking your ISO a little will still let you get moving subjects will low / very little image noise and remember this is just a rough guide - many times the sun will be much brighter than this built up garden surrounded by tall trees, buildings, fences etc etc... Out in an open field on a sunny day with no obstructions F5.6 at ISO 200 will happily get you 1/640th and above ! Note there is also still a good level of background blur and subject isolation at F5.6 and the detail in the foreground is more noticable than at the lower F numbers. For portraits with a group of people in it, even zoomed out, F5.6 is the minimum F number you should consider using to keep everyone in the group photo in focus from front to back ! Canon 24-70mm F2.8 USM L lens used.



Increasing the F number all the way to F10 even with a good amount of light is going to kill your shutter speed at lower ISO settings so if you want photos with plenty of detail but are forced to zoom in to get it and have to increase your F number to keep it in focus, as you can see the 1/80th shutter speed is going to leave you at risk of getting blurred shots and it just isnt worth having blurry photographs when just increasing the ISO setting will fix this problem and allow you to take high F number in focus photos when forced to zoom in ( which doesnt happen often, but it's better to know how to deal with it if it does !! ). If you still cant get the detail needed, then increase your F number more and ISO accordingly as it's better to have a photo with plenty of detail and a little noise than a blurred unusable photo due to a shutter speed that was too low !! 1/80th on non IS lenses is not recommended !! Canon 24-70mm F2.8 USM L lens used.



So after bumping the ISO up from 200 to 400 we now have a usable shutterspeed to capture a perfect non moving scene ( like this one ! ) with a much less blurred out background using the same focal point from F1.2 through to F10. If you wanted to do the same for moving subject, just increase your ISO setting until you can get the 1/640th + shutter speed you'll need.

And there it is, a look at the differences in shutter speeds and the various degrees of background blur you'll come across when shooting photographs from F1.2 all the way to F10 in ( mostly ! ) a sunny environment. Always remember to change your white balance ( WB ) before you start ( and when the weather changes ! ) Focus on any subject you want - in this example the focal point was the green leaves to the right but it's your photo so find the moment you want to capture, watch those shutter speeds and whatever your lenses F number capabilities, use them and have fun with it !