MTF charts, anybody?

Just curious. How many of you lens purchasers consult the MTF charts and how much of your purchase decision is based on it?

I have only ever really looked up the MTF charts AFTER I allready have the lens...

At which point I usually say to myself.. "yup,. I thought it was nice too"

Seriously,. I take word of mouth,. (of type?) and images I have seen as the largest influence... that and a trial when I have the chance.

I voted the last choice. :P Please explain haha.

Went for number 3 and i've yet to test my new lenses using the chart

Here's a good starting point:

http://www.luminous-landscape.com …s/understanding​-mtf.shtml

Ummm, it's not a chart for testing lenses. It's a result chart of a tested lens.
Actually, the MTF chart shows you in a graph form what the contrast and resolving power performance of the lens is at the widest aperture and another aperture like f/8 across the entire viewing angle of the lens.

I heard that the MTF charts posted on Canon's USA site are not accurate. Supposedly, the ones from the Japan website are more reliable. Nevertheless, I really don't know how to read Canon's MTF charts. They have so many plots that I don't know what each line represents. I know there are lines for horizontal/veritical MTF and diagonal MTF but their charts have 8 lines.

Even if I could read them, I don't think I would base my decisions on them. Another factor is that 3rd-party manufacturers don't supply these charts, so that would make it a bit hard to perform a comparison.

Actually, the reason I brought this MTF subject up was because I was browsing through my "EF LEns Works III" book this evening and came across a couple of pages showing the MTF charts of all the currently available EF lenses which I found interesting, especially when comparing different lenses. I wanted to hear from others who are knowledgeable about MTF charts, what they thought of them. Are they truly representative of lens performance across a broad range of samples or do they only represent a lens that was hand picked just for the purpose of testing them and getting good results?

It's actually not to hard to read the "jist" of the charts..

Essentially the straighter the line and the higher it is on the chart.. the better.. All of the best lenses have charts which read all four lines almost straight across the top.. like the

-------------300mm f/2.8 IS --------------- Or the 400mm f/2.8L--------

HTTP response: 404 | MIME changed to 'text/html' | Byte size: ZERO

slin100 wrote:
I heard that the MTF charts posted on Canon's USA site are not accurate. Supposedly, the ones from the Japan website are more reliable. Nevertheless, I really don't know how to read Canon's MTF charts. They have so many plots that I don't know what each line represents. I know there are lines for horizontal/veritical MTF and diagonal MTF but their charts have 8 lines.

Even if I could read them, I don't think I would base my decisions on them. Another factor is that 3rd-party manufacturers don't supply these charts, so that would make it a bit hard to perform a comparison.

Steven, I had a hard time with the MTF charts myself. No matter how many times I read through the brief explanations I still had a hard time understanding what the graphs were telling me. Then it became crystal clear when I read a more detail explanation in the "EF Lens Work III" book published by Canon. I guess it was more like I had different pieces to a puzzle but they didn't start to come together until I read this book.

CyberDyneSystems wrote:
It's actually not to hard to read the "jist" of the charts..

Essentially the straighter the line and the higher it is on the chart.. the better.. All of the best lenses have charts which read all four lines almost straight across the top.. like the

-------------300mm f/2.8 IS --------------- Or the 400mm f/2.8L--------

http://www.usa.canon.c​om …f_300_28/ef_300​_28mtf.gif http://consumer.usa.ca​non.com …ges/lens/ef_400​_28mtf.gif

A not so good lens looks like this;
http://consumer.usa.ca​non.com …lens/ef_28-200_35mtf2.gif

It doesn't necessarily have to be a straight line as long as the line are at or above 0.8 to be considered very good. If they're at least above 0.6, then they're satisfactory. Although a straight line does denote consistent performance across the entire frame.

For 1.6x cameras (20D, 10D, etc.) the lines should stay at or above 0.8 up until the 13 point on the horizontal axis. For 1.3x cameras, it should maintain that until the 17 point mark on the horizontal axis. If they don't, that means that you'll see a degradation in lens performance towards the outer edges or corners of the frame. For anything other than a FF camera, where the graph goes to the right of the point mentioned above isn't really that important since they fall outside the bounds of the sensor.

And this I picked up tonight. The thicker lines (the 10l/mm in the Canon MTf charts) represents lens contrast and the thinner lines (the 30l/mm) represents the resolving power of the lens. And last, but not least, the closer the solid lines and the dashed lines are to each other the more natural looking the blurred background becomes.

I like using the MTF charts for comparing lenses. My dissapointment is that Cannon does not seem to be continuing to make charts available for the more recent lenses. EFS types especially, so now I rely more on 3rd party tests. Some of which include MTF charts or scores. But they do not necesarilly correlate direclty with the Canon charts due to differences in testing. However one can use them when comparing reports from the same test lab. General tendencies will correlate accross different test labs, but the numerical values are not as transferable in an absolute sense.

Ok, I read Canon's description of MTF in their glossary. There are 8 lines in their MTF charts because they show results at two apertures (wide-open and f/8 ). Each aperture displays MTF using four sets of lines. Two sets are spaced apart 10 lines per millimeter parallel to a 45 degree diagonal, and the other two sets are spaced 30 lines per millimeter perpendicular to the diagonal.

But which lines should be above 0.6? If you look at the MTF chart for the 85/1.2L, the thin black lines are well under 0.6.

Once again, compared to the 300/2.8 the solid and dashed lines for the 85/1.2 don't look that close, but the 85's buttery-smooth bokeh is unmatched.

Well, there's a bit more to study with the charts, but here's some basic stuff.

All the blue lines are taken at f/8.
All the black lines are taken at maximum aperture.

Consider what maximum aperture is when comparing black lines, as an f/1.2 lens is not generally going to resolve wide open as well as an f/4 lens, if both are quality lenses. Always consider lens speed with looking at the wide-open MTF curves.

The fat lines are measured at 10 lines/mm and indicate the lenses' contrast capabilities.
The skinny lines are measured at 30 lines/mm and indicate the lenses' resolving (sharpness) capabilities.

The horizontal axis of the chart indicates the distance from the center line of the lens. The farther right, the farther from center. The scale in mm is along the bottom of the chart.

On the verticle scale is a scale of 0 to 1, with 1 being the perfect fidelity, and 0 being no image at all. The closer to 1 the readings are, the better the image fidelity. Quality at f/8 is usually much higher than at maximum aperture.

The solid lines are measurements made in the Sagittal plane (radial from the center).
The dotted lines are measurements made in the meridional plane (circular, perpendicular to the radial lines being measured).

Generally, the closer the dotted and solid lines remain together, the smoother the bokeh.

fa! 85mm f/1.2L Pooo.. look at that chart,.

Now here's a chart! (500mm f/4L IS)

HTTP response: 404 | MIME changed to 'text/html' | Byte size: ZERO