It may sound funny but your lens or lenses all have a personality. And you need to unlock it's personality to get the best from it. Here's how...
The aperture & diffraction test...
One of the the most important tests you can do with any lens is to run through the apertures. This can help you find the "sweet spot" and more crucially discover when diffraction is starting to creep in and you start losing image quality.
Scroll down for a detailed cross-section of apertures from the Sony 20mm FE 1.8 G lens...
"Hello! So today we're taking a break from the back garden and i'm still heading out locally i'm on burley moor which sits just above the village. I'm testing out a new lens that i've got it's a 20 mm fixed focal length lens, that means it doesn't zoom in or out. I'm going to do some tests with it that i'm going to talk you through why and what i'm hoping to achieve with this test first i've gotta get to the top...
...Nope not that hill! The next one.
I don't know whoever you've ever thought of this but every lens has its own kind of character or personality. It has things that it does really well and things that doesn't do very well. You know some lenses are better performing as portrait lenses some as landscape lenses they all have their different quirks and what we're doing today is to test out this new lens and find out how it's going to perform best and i don't know that until i start testing it out and seeing what it does and today's test is to test out its optimum aperture.
So welcome to one of my favourite spots on Burley moor I absolutely love this view. I love it up here, it's a little bit higher up so it's a bit quieter but we've got a little bit of wind coming across because we're high up which will blow over the mic so i hope you'll forgive me and bear with me as we do this it'll be short and then we'll be back in the studio. Now the reason i'm up here is because i want to test this lens and work out what the optimum aperture is for landscape situation.
Logic dictates the higher your f number the smaller the aperture the more depth of field and the clearer the picture is going to be unfortunately it's a little bit more complicated than that because as we go up as we shrink that aperture we start to introduce this element called diffraction which kicks in differently on different lenses and what we're doing today is we're here we're going to work our way through each of the apertures and we're going to find out at what point that diffraction kicks in and at what point we get the real optimum quad image quality so we can we i mean we could just google it right so we could just stay indoors and google it but i really believe in that practical application really helps things to sink in and helps you remember when you're out with this lens i'm gonna know what the optimum f number to use on the camera and this lens setup will be as a result of going through and then looking at the photographs afterwards so that's what i'm going to do now.
So thanks for joining me back at the lab. I'm gonna try and go through these as quickly as i can. i've already removed some of the excess apertures so just to go over very quickly what we did while we were up on that more we set up the camera on a tripod and made sure the tripod was nice and steady put an iso 200. On set it at iso 200 because we want to try and maintain that quality that iso quality so we can compare and contrast each image we set it on aperture priority and then work through the aperture range of the lens.
So we can go through each of those apertures and see how the lens performs now what i've done here is i've picked out key apertures. i've gone for each one looking at each different point but the key aperture points for that's beneficial for this lesson because i don't want to waffle and waste your time by going through each and every single one.
So i've sort of highlighted and separated out key f numbers so when i talk about f numbers i tend to talk about high f numbers and small apertures so the higher the f number the smaller the aperture because it can be quite quite a tricky thing to get your head around sometimes when you when you're first starting to grasp.
The idea of photography and that kind of the high number means a small aperture hopefully uh that'll come across clear enough. So we're here looking at f22 here you can just see in the top right hand corner the information of the image here. That's why i've highlighted that there was on a strong sturdy tripod with no risk i also should point out we did a two second timer on it so my hand didn't jog the the camera when i was taking the picture so i was using two second timer. i could have used the remote but anyway.
So 50th of a second handheld would be a bit risky but on a tripod we're all good and when you look at the back look at this photo here in lightroom it kind of looks like it's okay as it would on the back of the camera. and i think this is the danger and and i do come across this quite a lot with uh particularly with the virtual lessons that i've been doing where people have used their you know they've got they've you come out. And and i learned exactly the same way.
You know when you start to learn photography, the higher the f number the smaller the aperture the bigger the depth of field so the clearer the picture is from front to back and you know the i think there used to be a publication out called f64 because that was like the ultimate you know kind of depth of field thing and um you come away from those lessons thinking right i need to just make sure i'm on f22 to make sure i get the best clearest picture particularly when i'm looking at landscapes and actually you know, what this test will show you and demonstrate is that actually where diffraction kicks in and where that optimum aperture for your optimum image quality. As you can see just looking at it like this it looks fine and and you look at some of the other ones they look exactly the same. And it's not until you start looking in to the detail that you start to notice what's going on so this is at 100 zoom so you zoom in at 100 and then actually that marks looking a little bit fuzzy and that background's starting to look a little bit muddy as well and then you go in at 200 percent and it's actually a lot not quite as clear and as sharp as you were hoping. Now you would, i think on the face of it start to think (and this is the danger really). You start to think i've got camera shake here that's annoying and that's that's kind of what you'd think. But experience tells me that it's actually diffraction starting to kick in.
So let's move on to the next photo. f16. Landscape photography kind of traditionally celebrate f16, that's like known as that sort of sweet spot where on the camera. Where you get that optimum quality and depth of field so it'll be interesting to see what we get on f16 so let's zoom into 100 first. Okay that rocks definitely clearer and sharper and that background's looking sharper 100 let's switch it to f22 can you see hopefully you can see that so fuzzy muddy f22 clearer and sharper on f16 let's go into 200.
Okay so it's sharper it's clearer still a little bit muddy particularly in there now i also should probably point out that i focused on the rock point here. Just so i had a consistent point of focus an easy and consistent point of focus to go through the test. I didn't want to have different points of focus on each one if i was doing this as a proper photo i was setting out for a big landscape i'd maybe work out the hyper focal distance or maybe think about focus stacking the shot from front to back. But because this is just the test we're going through it and we'll just want as many elements as consistent as we can so we can do a fair comparison and you can see that at 16 it's definitely better than f22 it's definitely clearer,
Let's go to the next one f11. Now this is where i've been spending started to spend a lot more time before recording. Looking in detail at each one but to me that background on that hill and actually you know just generally everywhere is starting to look a lot clearer and sharper at f11.
i'm hoping you can see particularly in the background but all in the rock as well you can actually see that sharpness start to ping. It ping in when you change between the two.
And i think it's such a surprising thing particularly you know maybe you know about diffraction but it's still always fascinating to see. But if you're not aware of diffraction when you see this it's like mind-blowing because you kind of your brain's sort of just adjusted to work out about f 22 and all that and then suddenly you started to look at something i mean that quality for me f11 to f16 is is quite significant actually when you're zoomed in at 200 even 100 say.
And then what i've done to save you a little bit of time really i've gone through each of these really closely and i i started going between f8 and f11. But really the conclusion i came to was that actually f9 is that kind of real optimum performance on this lens on this 20mm lens. At f9 and it's a close call between f8 up to f11 but just edges it slightly having had a little real close look across each each part of the photo and and exploring it.
That's really useful to know and if you've got um a head like mine one of the things you can do - when i say head like mine. like a sieve! - and forget everything right! So one of the things you could do is you could put a little sticker on the lens cap saying f9 and then you know that at f9 you're you're getting the optimum picture quality from your photograph. and uh not only is it good to know that you've got that f9 you could put "f9 (f11 to f8)" because then you know that that's where you're firing your optimum photos from. It's so such an important thing to do whether you've got a new lens or whether you've got an existing lens and you don't know at what point that that diffraction starts kicking and you start to lose that image quality. because if you don't find out before you might find out later at a really important point.
If you're going on a holiday for a lifetime you know maybe not in the next couple of months with lockdown but like in in the in the future you might decide to book yourself something really nice, a once in a lifetime really special or you might just be out on a walk and see some kind of spectacular cloud arrangement or light and and you want to capture that and if you don't know what the best aperture for that lens is, you're really gonna you know you're really gonna struggle or you're gonna get really frustrated when you look at the photographs after.
so once you know that you don't need to do this test you could still do handheld like you know if if you're out on a walk and then you see you know a rainbow or thunderstorm or whatever. Something really cool you can then say right i'm on f9 i haven't got my tripod with v but i can shoot the iso up to 800 because that at f9 i'm getting that perfect quality and then you just keep an eye on that shutter speed.
But i'm i'm digressing a little bit from the point of the exercise which was to find out our optimum f number. and what you know the whole point of this exercise was to sort of understand the character of your lens and start to understand how it works and how it performs.
Here's a shot that i took just after actually. Just as i was packing up we got a break in the light and it came through and picked it up quite nicely. at this point obviously i hadn't done the test but i had a i suspected that a f11 would be a an alright aperture to use for this.
And you can see actually if i go into file info... this is great, you know, so when i was learning photography learning the ropes at art college and all that. We used to have to (i was really bad at it i have to confess) but we had to write down each exposure, each you know each shot you did you do your number on your film and then type in the shutter speed, you'd write it down in your notepad and oh it was horrible! But now you don't have to do any of that just right click or look at the camera info and here you can see f11, iso 200, 400th of a second and the other interesting thing it also tells you the focal length that it was fired at as well which is useful and as you can see if i go into 100% view, you can see the picture quality there is really really nice throughout the image.
Now with any wide-angle lens you're gonna get start to get a little bit of softening towards the edges but... you know i'm gonna stop using that mouse because it makes that horrible sound doesn't it ? sorry about that! and um you can see here that the quality really is quite special there and let's contrast that with the... so with the camera that i was filming with was a 24 it's my 24 to 70 mm.
It's a canon 24 to 70mm f2.8. It's a not a cheap lens and the thing with that lens is it's my workhorse lens. okay, so it's the lens that i take to every single job i do i'll take it away on holiday as well, it gets the job done, it's really reliable, it's got fast autofocus i know it really well. when you're working on a job you could be in a really small tight space or you could be out in the landscape doing portraits in the landscape or whatever so it it's really reliable when i take it everywhere. But it's really interesting to compare in this situation because actually we can have a look at ,i'll share the info now quickly with you file info camera data okay so at focal length 24 millimeters 125th of a second, f 8, iso 100, so it's not massively fair comparison but it's it's never going to be anyway. But i know that at f8 that tends to be the optimum picture quality i'm going to get from the 24 to 70. so that's why it's at f8. One of the things i would do if i was doing this as a proper landscape i would move in to about 28 or 30 mm in the focal length because i know for a fact that at 24 mm i start to get softening around the edges on this lens.
so quite often (and this is where it's key to understanding your lens right) so you kind of know you're not you're not meeting any nasty surprises that's the key you're not going to get something that's making you "ahh" and so normally what i'd do is if i was doing a landscape with this lens i'd just zoom in a little bit with that lens so it was sort of 28 uh 30mm like i said somewhere like there and then that would minimize it, wouldn't that see this softness over on this edge it wouldn't be as bad as you get at 24 with this with this particular with my lens here and you can actually see that there is like whilst that rock is sharp and these rocks are sharp they're nowhere near as sharp as that 20 millimeter.
And that's that thing with prime lenses okay. So that's when people go on about how the picture quality of prime lenses that that's a really clear example so let's have a look at you know you know look at how sharp that is.
it really is and um you know it's tricky isn't it because you know it's just one of these rabbit holes that some photographers go down. It's like oh you just the quest for precision and honing your craft and and it's a good thing to do and it's not bad if you don't decide to go down that right path but you know it's an interesting thing when you start to see that kind of picture quality especially if you want to start making prints and and start doing big prints of scenes and spectacular sites and stuff like that. So it's really interesting to see that difference in sharpness and clarity you know the other point to make really, actually if you do use a zoom lens, it will, that optimum quality will differ as you zoom in and out. So if you're going to do a test with a zoom lens what you want to do is you want to test it at different key focal lengths.
so for example if i was doing my 24 to 70 mm. i'd probably go through that aperture range at 24 then 30 go through that aperture range again and then 50 go through the aperture range again and then 70 and go through that aperture range again.
and then you know you have this kind of deep understanding of how that lens is going to perform at different apertures uh in terms of picture quality.
In terms of understanding, it is me knowing with this lens this stick with the 24-70, me knowing that there is this kind of softness around the edges. It also allows me to you know sometimes it's not quite as important if you're doing portraits, but it just means that i often leave a little bit of extra space to crop in around the edges and then i know i'm not, you know, it's that thing it's just making sure that you're not hit by a nasty surprise. Because there's nothing worse than sort of thinking that you've taken some really great photographs and then getting them on the computer and realisng... oh they're not as great as i was hoping! and this is a big step to doing that.
Understanding your lens and how it's going to perform and react to different situations. So i hope you found that interesting i think it is quite a key thing really and it's as much as understanding your camera as to understanding your lenses as well and it's a big step to really improving and getting a jump in that quality of your photographs.
So i hope you find that interesting and beneficial and i hope it's something that you can apply in your own photography. Thank you."