When someone tells you that something defies description, you can be pretty sure he’s going to have a go at it anyway. - Author Unknown
A lot of my posts about lens resolution consist largely of showing the MTF 50 numbers from Imatest or our optical bench. That leads to a lot of questions about what that numerical difference really means, and how much you would notice it in photographs.
My usual response to that has been more numbers: SQF data that shows how large of a print would be required for you to see the difference at close viewing angles. But photographers are visual people and more numbers don’t always seem to answer the question. So I thought we’d try to show what a difference in MTF 50 numbers really looks like.
This is harder than you might think. I’m trying to use your monitor, at 72 dots per inch but with a huge color gamut, to demonstrate the difference you would see in a print at 300 dots per inch but with a smaller color gamut. The most accurate way to do it would be to invite you all over to look at some prints, but that’s not practical.
Today’s Testing
We’ll try something I think will usefully demonstrate what the numbers say and what you can see.
1) I’ll test specific copies of several lenses and give you their MTF50 measured by Imatest.
We’ll use ISO 12233 charts with the same lenses and show you 100% crops. It’s certainly the most used, and probably the most sensitive, of the optical charts for testing resolution. This should demonstrate what kind of difference a thorough home tester could see.
OK, I’ve taken a long route, but narrowed things down to a Nikon D800e based system, a Canon full-frame system, or a Pentax K-5 IIs system. All of them met my needs just fine, although the D800e system gave me better image quality and the Pentax a bit less.
Let’s Begin With: Don’t Do What I Did
Sometimes the main purpose of my life is simply to serve as a warning to others. By now it should be apparent that I made some major mistakes.
Foremost was that I overreacted. Following my lifelong philosophy of ‘Anything worth doing is worth doing to excess’ I decided to exit Micro 4/3 when I found it didn’t fit all of my needs. Despite the fact that I said, very clearly, when starting this that I knew there was no perfect camera system, even for one individual. The grass will always be greener in some area on the other side of the fence. Continue reading →
Lensrentals is an awesome place to work, and we’re looking for some new people to join our team. We offer great benefits for our employees, including health/dental/vision insurance, 401(k), paid vacation and free equipment rentals, combined with a fun & extremely casual work environment.
It’s not falling that hurts, it’s the sudden stop at the end.
-Author Unkown
Understandably, people are concerned with whether a new lens they buy is functioning properly and optically within specifications. One thing I harp on is that we also need to watch our lenses over time. Bumps, drops, and normal wear-and-tear can affect a lens optically. Continue reading →
In my last post I made a preliminary list of systems I was going to consider. Some people are a little surprised I’m considering crop sensor cameras. I’m surprised that they’re surprised. I’ve shot with a micro 4/3 system for months and it certainly met 80% of my needs, so an APS-C based camera may be just fine. Or I may decide that I need to have a full-frame camera. I’ve generally shot full frame for the last several years.
But did I mention this is coming out of my own pocket? And that I’m kind of cheap? It’s been several years since I’ve actually priced systems but the last time I checked APS-C was a lot cheaper. I want to look at just how many of my hard earned it requires to join the Big Boy Full-Frame Camera Owner’s Club. I may just hang out with the kids.
I also want an idea, before I start comparing systems, about the cost difference between the different systems. I know exactly what the cameras sell for, but that doesn’t necessarily reflect the cost of buying into a system. (Oh, and for those of you who think I have these numbers floating around in my head, I haven’t done Lensrentals’ purchasing for almost two years. I’m way out of the loop.)
As I mentioned in my last post, I have more time for photography now than I have for the last several years so I’m buying a personal camera system. While I can ‘borrow’ stuff from Lensrentals for a specific shoot I can’t just take a system and keep it at my house permanently.
My rule of thumb has always been if I need something 2 or 3 times a year, I’ll rent it, but if I need it more frequently than that I should buy it. Over the last few months I’ve found myself shooting with something different than my current system (Olympus OM-D E-M5 based) at least once or twice a month. It seemed time to investigate my options.
The purpose of this post is NOT to convince you that my choices are right for you. What I need and want in a system isn’t going to be what you need and want. The process I use to reach the decision may be interesting to some of you – I certainly get a half dozen emails a week asking how to choose a system. For most of you, though, who already are locked into a system, these couple of articles will not be very interesting. I apologize and we’ll return to our regularly scheduled blogging in a week or so.
Note: I’m going to bore people for a week or two while I decide on a new camera system for myself. To alert those who are going to be bored by posts about “Roger Buys a Camera System”; I’ll put that in the title for the rest of this series.
I don’t own an SLR – I go check one out for ‘testing’ when I need one. But I’ve moved out to the country and I want a camera at the house. I can’t really justify to management that I need to test a camera and some lenses for a year or two.
I know what I want: the Canon T4i‘s touch screen, the Canon 6D‘s Wi-Fi, and the Canon 5D Mk III‘s autofocus built around the Nikon D800E sensor, Nikon’s flash system, Pentax’s user interface (I’d take their sensor too, if I went crop frame), and be able to mount lenses from all manufacturers. But given a far-less-than-unlimited budget, I’ll be making some compromises, like everyone else. In order to make comparisons, I want to take a look at exactly how some systems differ.
Most of that doesn’t involve geek stuff like this, but geek stuff is what I know best so that’s where I’ll start. Resolution isn’t the end-all point for deciding on a camera system. It isn’t even the most important point in my decision about a camera system, and I’m a resolution nut. But it is a thing I want to know about.
A Resolution Comparison
One of the things I constantly harp on is that people should not compare Imatest or DxO results on two different cameras. You can’t look at the results of a lens on a crop sensor and a full-frame, for example. You can’t look at results of a lens test on a Canon 5D and make good predictions of how it will behave on a Canon 5D Mk III. We’ve even found lately that you can’t take the results on a Sony NEX-7 and extrapolate to a Sony NEX-6.
But there is one thing you can do fairly reasonably. You can compare two systems (camera and lens) to each other and determine the overall resolution of each system. I had some pretty self-centered reasons for doing just that. I, the ultimate camera system commitophobe, am going to have to buy, with my own money, a camera system. I hate when that happens.
A few days ago I learned about the Metabones Speed Booster. For both of you who haven’t heard yet, this is an adapter containing optical elements and electronic controls that allows you to mount Canon EF lenses to Sony NEX cameras (other versions are planned for other lenses and cameras). The quick summary is the adapter is the opposite of a teleconverter.
A teleconverter spreads out the light leaving the lens so that only the center portion reaches the sensor. The result is the focal length of the lens seems longer (the image is magnified), but at the cost of reducing the amount of light (effective aperture) of the lens. The Speed Booster compresses the light leaving the lens onto a smaller image circle. This makes the focal length seem shorter and actually increases the amount of light reaching the sensor.
The Metabones’ Speed Booster compresses the light leaving the lens into a smaller image circle. Image credit Metabones http://www.metabones.com/images/metabones/Speed%20Booster%20White%20Paper.pdf
