MTF Chart and the buying decision.

MarkM6

I would like to know how much does the MTF Chart influence your buying decision on a Lens?
:ear

gus

What is MTF Chart?

MarkM6 wrote:

I would like to know how much does the MTF Chart influence your buying decision on a Lens?

I didnt know it existed. I just searched shots for my lenses & decided from that

Bob Bell

High

I always check MTF charts and really look for whats happening past 10mm from the center. I also look at them for resolution which is often very telling of the optically quality of the glass used.

MTF charts only show the capability under lab conditions so its a starting point on buying a good lens.

Antonio Correia

Medium

I like this kind of techical data.
But the interpretation is rather difficult.
Quite interesting though I have not bought my lens by this.

MarkM6

I see this coming from AZ Bob

Bob Bell wrote:

I always check MTF charts and really look for whats happening past 10mm from the center. I also look at them for resolution which is often very telling of the optically quality of the glass used.

MTF charts only show the capability under lab conditions so its a starting point on buying a good lens.

I knew Bob looks at the MTF Charts because;

Bob Bell wrote:

I disagree with some about zooms vs primes. There are zooms out there that outperform primes when it comes to line resolution.

USAIR

gus wrote:

I didnt know it existed. I just searched shots for my lenses & decided from that

Me too Gus and also the reviews

Any good link on how to read these
Seems I have seen a mag article but skimmed over it

Fred

MarkM6

Here is a link on LL

USAIR wrote:

Any good link on how to read these

Here it is Fred...
http://www.luminous-landscape.com/tutorials/understanding-series/understanding-mtf.shtml

Bob Bell

High

MarkM6 wrote:

I knew Bob looks at the MTF Charts because;

I am not that predictable. I wonder if you predicted I would say that, did you predict that I would predict that you would do that so I wouldnt write this? I didn't think so

MarkM6

Hell yah...

Bob Bell wrote:

I am not that predictable. I wonder if you predicted I would say that, did you predict that I would predict that you would do that so I wouldnt write this? I didn't think so

Yes I did. What if I've read your 475 previous posts. I won!

Happy 5th to you AZ Bob!

ziggy53

MarkM6 wrote:

I would like to know how much does the MTF Chart influence your buying decision on a Lens?

MTF charts only represent a particular lens that was tested, except when the manufacturers test, and then the manufacturers can't agree on the standards and procedures. You can't compare MTF results unless they are performed on a batch of lenses, under the same situations and circumstances, by the same individuals, following positively anal retentive methodology.

---

This is from "Luminous Landscape":

"[FONT=Trebuchet MS, Arial, Helvetica]You should note here that different manufacturers provide different MTF frequency measurements. One company may provide 5 lp/mm graph lines, which makes their lenses look good. These lines are often very close to the top boundary of the chart. Other manufacturers may provide lines for 10 lp/mm as the coarsest structures they measure. The two shouldnþt be compared directly. In fact, MTF charts from two different sources shouldn't be compared directly, either. There are enough experimental and procedural variations to make direct comparisons meaningless."[/FONT]

---

My own method is to "glance" at the MTFs when available, but they are way down on the list regarding my actual purchase influence.

ziggy53

Harryb

What is MTF Chart?

MarkM6 wrote:

I would like to know how much does the MTF Chart influence your buying decision on a Lens?

Not at all.

Bob Bell

High

ziggy53 wrote:

MTF charts only represent a particular lens that was tested, except when the manufacturers test, and then the manufacturers can't agree on the standards and procedures. You can't compare MTF results unless they are performed on a batch of lenses, under the same situations and circumstances, by the same individuals, following positively anal retentive methodology.

---

This is from "Luminous Landscape":

"[FONT=Trebuchet MS, Arial, Helvetica]You should note here that different manufacturers provide different MTF frequency measurements. One company may provide 5 lp/mm graph lines, which makes their lenses look good. These lines are often very close to the top boundary of the chart. Other manufacturers may provide lines for 10 lp/mm as the coarsest structures they measure. The two shouldnþt be compared directly. In fact, MTF charts from two different sources shouldn't be compared directly, either. There are enough experimental and procedural variations to make direct comparisons meaningless."[/FONT]

---

My own method is to "glance" at the MTFs when available, but they are way down on the list regarding my actual purchase influence.

ziggy53

Ziggy making the statement that you shouldn't do that is seriously flawed. Proper MTF testing is done on a bench tester usually using the 50% MTF testing methodology also referred to MTF 50. The output of these tests are not lp/mm they are in lw/ph. There are a lot of crappy tests, testing the wrong thing but to dismiss all of them is foolish at best. I would not put michael as an expert since there are established MTF testbed out there and manufacturers like Zeiss and Leitz (Leica) use them.

One of the interesting sources of MTF tests is Photozone. He seems to test them all using the MTF 50 methodology but I don't know what equioment he uses.

To ignore an important tool in the judgement of a lens is like buying a car without reading dyno tests, road tests, etc... Sure they are on different days with different track tempertures but they are still accurate and viable.

But maybe its better to buy blindly so there is a reason for excuses later.

Matthew Saville

High

I know MTF charts are not all-telling, and I know (or at least I hear tell) that the MTF comparisons vary by manufacturer.


...But I also know that a bunch of horizontal lines are a gooood sign for any MTF chart. Which is why I loooove my Sigma 150mm!!!




Sharper in the corners than it is in the center? Not bad at all!

-Matt-

MarkM6

Sigma 150mm f/2.8 EX

Matthew Saville wrote:

Which is why I loooove my Sigma 150mm!!!

You are not kidding, Matt... this lens is freaking awesome; :wow
http://www.pbase.com/cameras/sigma/150_28_ex_dg_macro_hsm

ziggy53

Bob Bell wrote:

Ziggy making the statement that you shouldn't do that is seriously flawed.

Bob,

Reread my comments, I never said "you shouldn't do that".

Bob Bell wrote:

... Proper MTF testing is done on a bench tester usually using the 50% MTF testing methodology also referred to MTF 50. The output of these tests are not lp/mm they are in lw/ph. ...

Really? I did not know that.

Bob Bell wrote:

... One of the interesting sources of MTF tests is Photozone. He seems to test them all using the MTF 50 methodology but I don't know what equioment he uses. ...

Curiously, PhotoZone does publish using lw/ph, as you allude, but they describe the MTF using lp/mm, and I can't find a discussion comparing the two technologies or even a discussion whether they are comparable.

http://www.photozone.de/3Technology/mtf.htm

Bob Bell wrote:

... To ignore an important tool in the judgement of a lens is like buying a car without reading dyno tests, road tests, etc... Sure they are on different days with different track tempertures but they are still accurate and viable. ...

I have never purchased a car based on the performance specs or "dyno tests". I purchase my cars based on how they respond to my driving style during an actual test drive.

I am not the most cautious or carefull driver either. My first car was a 1967 Mustang convertible, with aftermarket (Addco) sway bars front and rear, "FelPro" racing gaskets so I could take off the rocker covers and crankcase for inspection, heavy-duty shocks all around, slightly larger tires (but lighter so they wouldn't overload the springs or affect braking), custom exhaust (my own design with "Cherry Bombs", ooooh), tweaked carb and tweaked timing. I also manually adjusted the lash on the bearings in the differential to equal out the torque to the rear wheels. I used to shut down cars with larger engines and I could run circles around others' for in-town road races. I paid attention to the details and it paid off. ... I also got my share of tickets. (I kept the first one I got, from a rookie who later became the Chief of Police, and a friend.)

Anyway, I buy lenses by researching everything I can about them. I read every review and test I can find. I look at other folks results on PBase. I look for anecdotal and other empirical findings, from any and all sources. I do look for MTF data, but it isn't a major derterminant in my descision making process.

Ultimately, I buy according to the best information I have at the time. If further testing indicates the lens is unsuitable for my needs, I send it back.

It's just that simple.

Bob Bell wrote:

... But maybe its better to buy blindly so there is a reason for excuses later.

Not hardly! I only own lenses that I have personally tested and graded, whose qualities are assesed by me, for my purposes, and found to be acceptable for their intended purpose.

I recently sent back two lenses (which had great MTFs, BTW) which didn't pass "my" testing. I wound up buying the venerable Canon 70-200mm, f2.8L (non IS), and I kept because it passed "my" tests, not because it passed someone elses' tests. If it had not been acceptable, it too would have gone back.

Later,

ziggy53

Liza

You left out the response, "I could care less about MTF charts." I usually check out user reviews on Fred Miranda's site and recommendations by posters on POTN before I buy a lens.

ian408

There are many ways to select a lens. Of which, measurebaiting is one.

I suppose one could spend lots of time reviewing all of the technical specs
and analyzing the MTF charts to the nth. But what really matters here is
whether the photographer and his/her equipment make good photographs.

MTF charts are a component of your purchase decision but they shouldn't
be the only decision making tool.

Antonio Correia

Medium

ian408 wrote:

MTF charts are a component of your purchase decision but they shouldn't
be the only decision making tool.