One of the ways that you can judge the image quality cannon actually post this on their website is thie empty f charts which judge the sharpness of your images and so this is what nmpf chart looks like and what it's doing is it's ranking the sharpness from the centre to the edge of the frame in different types of areas of contrast and so at zero line that is the center of the frame as we go out to five ten fifteen twenty that is the edge of the frame and you'll notice that these and like I said I'll give you the other statistic everything above point six is considered sharpe everything above point eight is considered very sharp on the lens on the left the centre of the image is super sharp and it gets a little bit weaker as it gets out to the edge of the frame this second example shows this lands is pretty sharp in the middle but once you get away from the middle it loses a lot of sharpness and it's going to be soft on the corners and so this is less than desirable what you ideally wan...
t is a line straight along the top and you can find these empty f charts for all the different lenses out there a little side note to just kind of funny little thing these were all theoretical and they're not actual so this is all what the lens designers theoretically think is happening in your lands. And there are different ways of testing them. And what they published is theoretical ones, not the actual ones. But there are places that you could look up online if somebody has done a test to see exactly what they look like. D x o mark is an interesting place I think they're out of france and they measure cameras and lenses for quality in many different ways and one of the ways that they can do it is by doing kind of a collection of a lot of features so they're not just judging a lens on sharpness they're looking at how much distortion vignette ing transmission chromatic aberration and they're doing a balance up where which lenses over all the better lands and they kind of have different waiting's on these as to how good the lenses are and I decided to go and look up the cannon lenses and pull off the list of the ten worst lenses that cannon makes according to their standards here and so here's our list of ten lenses thes air their bottom ten lenses and you'll see a lot of zoom's a lot of slow actress slow aperture zoom lenses on here and you do have to question their ranking system and their methodology because it's in perfect because there are lenses on that list that I would have no problem recommending using their lenses that I would have no problem using and getting great images off but their ranking fairly low in this particular case now let's take a look at their top ten lenses and what you'll notice is a large number of el lenses but interestingly the top two are not ellen's is in fact the number two position linds is a twenty plus year old leads very old technology sharpness wise it's not one of the ten sharpest but all these other features are quite good so it actually ends up very high in the ranking system and so depending on how you play with these numbers this is a very subjective number here but yes all of these air fantastic really nice lands is interesting number ten on the last one hundred fifty dollars lands you can get one of their top ten lenses for one hundred and fifty bucks fact a couple of these lenses are well well under a thousand dollars and because I don't work for cannon and I don't care about promoting or not promoting cannon let's take a look at the ten best non cannon lenses and what you're going to see here is a lot of lenses from zeiss we'll talk about sights in the next section sigma has been doing really well with their lenses and so they've got some in there and holy smokes number nine sam yang how did they get in there they're they're kind of their kind of new kid on the block or in this type of arena but they made a lands it's really sharp it ranks up there it's not that much money and so those are some of the top ten and bottom ten not really a big deal but the diaphragm the aperture in your lands is controlled electronically. It's powered electronically and amazingly, they've had no real improvements or changes since the day it came out. It's, a fully electronic transmission, and there's really been nothing. It's worked perfectly since day one, and so it's better than the mechanical systems that some other companies are still using and it's in all the f lenses and there's. Really no differences in it, but that's just part of what's going in the lands. Internal reflections. We talked a little bit about this before it causes flare ghosting it's when light is bouncing around, and so the design of the lens and the construction of the lands have a big part in tow, how much light is bouncing around cause we want light that goes straight through to the image sensor, so they put all these reflective coatings on the edges of it. In fact, if you've looked in some of the back of some lenses, it's, kind of like the soft black felt in material and it's that filter material, because that just absorbs the light and it doesn't reflect off of it. And that's, what the flocking iss. Even the design of the aperture khun reduce the amount of flair and ghostie they actually sometimes have little blocks in grooves and little areas where it just blocks a little bit of light that would normally come in and cause a problem in there and some of these air actually moving back and forth there's no lens element it's just trying to block some of the light that's moving from just a little side note here a zoom lens is a lens that can change focal length and maintain focus most people I would I don't even know because it's not clearly stated but we have a whole bunch of zoom lens is what we call zoom lenses but they're not really zoom lenses what they are in actuality are very focal lenses and a very focal lands that changes focus as you change the focal length if you've ever focused on something and zoomed in on it and it's no longer in focus that is a very focal lattes it's much easier to make a very focal lengths than it is a zoom lens it would be preferable to have a zoom lens where it holds the focus but this is why we no longer use the technique of zooming into focus and then pull back and taking the picture because your camera or your lens may change focus and so you should focus at the focal length that you plan to take the picture out 00:06:35.06 --> 00:06:37. some of the lenses suffer from creep, not creeps. Creep creep is where you're carrying a lands we see worse one of these lenses. Reversed here. So the one hundred, four hundred if you're carrying it like this, if certain positions it could get kind of loose, it kind of creeps out on you like this. And as you're carrying lands, it kind of gets a little long. It's, like, no, you keep it up here and sew. A number of lenses will have a lock on it so that it doesn't. There, it is it's creeping on me. The weight of the lands is carrying it out, and so there's a number of lenses that have a lock on it and it's just simply for when you're walking around and you don't want the lands extending out, banging around on stuff the cannon, pf, mt. Is fifty four millimetres across the nikon lens is forty four let's do a little math fifty four forty for it means kanan is bigger than nikon what about that flans distance the flans distance is forty foreign cannon and forty six point five you know what this means this means is that we can make an adapter noble flex makes one and we can mount it on her camera body and we could mount a nikon lens on our camera body the last thing is they have been making improvements along line so there's a bunch of seventy two to hundreds this is an old one it doesn't have image stabilization and so this is known as the non s model the next one has image stabilization on it it says I asked we call it version one because now there is a version two out that actually is labeled as version too console as they make improvements you'll see lenses get replaced into these second versions so if you want to find out how old your lenses there is a date code on your lands now from nineteen sixty two thousand eight they were using this six letter to letter four number code and I'm going to give you the key code here and this is where the pdf will come in handy is the first letter refers to the factory where it was made the next one is the year you in this case if we look on the list was either nineteen, eighty or two thousand six. We consume eyes. It was two thousand six, because it's, an autofocus, lands oh eight is the month that's pretty easy to figure out. And if you can figure out what the last one is. O nine. You can give me a ring, and I'll put it in my next class. And so that's, how you figure out how old it is. But currently they're using a ten digit system where the first two digits are a date code of the year and month that it was made, according to this chart, that you see on screen now, and twenty seven, if we follow. The list is march of two thousand fifteen, and they're just adding a new date each month to the numbering system. Assuming that this goes forward, you can kind of follow it and figure out what it is in the future. But if you want to figure out the date that your lenses manufactured, this should get you very close to that date.