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Measuring Lens Variance

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Warning: This is a Geek Level 3 article. If you aren't into that kind of thing, go take some pictures.

I've been writing and discussing the copy-to-copy variation that inevitably occurs in lenses since 2008. (1,2,3,4) Many people don't want to hear about it. Manufacturers don't want to acknowledge some of their lenses aren't quite as good as others. Reviewers don't want to acknowledge that the copy they reviewed may be a little better or a little worse than most copies. Retailers don't want people exchanging one copy after another trying to find the Holy Grail copy of a given lens. And honestly, most photographers and videographers don't want to be bothered. They realize lens' sample variation can make a pretty big difference in the numbers a lens tester or reviewer generates without making much difference in a photograph.

It does matter occasionally, though. I answered an email the other day from someone who said, in frustration, that they had tried 3 copies of a given lens and all were slightly tilted. I responded that I'd lab-tested over 60 copies of that lens, and all were slightly tilted. It wasn't what he wanted to hear, but it probably saved him some and his retailer some frustration. There's another lens that comes in two flavors: very sharp in the center but weaker in the corners, or not quite as sharp in the center but stronger in the corners. We've adjusted dozens of them and can give you one or the other. Not to mention sample variation is one of the causes that make one review of a lens say it's poor, when other reviewers found it to be great.

At any rate, copy variation is something few people investigate. And by few, I mean basically nobody. It takes a lot of copies of a lens and some really good testing equipment to look into the issue. We have lots of copies of lenses and really good testing equipment, and I've wanted to quantify sample variation for several years. But it's really, really time-consuming.

Our summer intern, Brandon Dube, has tackled that problem and come up with a reasonably elegant solution. He's written some Matlab scripts that grab the results generated from our Trioptics Imagemaster Optical Bench, summarizes them, and performs sample variation comparisons automatically. We're going to eventually present that data to you just like we present MTF data: when a new lens is released we'll also give you an idea of the expected sample variation. Before we do that though, we need to get some idea of what kind of sample variations should be expected.

For today, I'm going to mostly introduce the methods we're using. Why? Because I'm old fashioned enough to think scientific methods are still valid. If I claim this lens scores 3.75 and that lens scores 5.21, you deserve to know EXACTLY what those findings mean (or don't mean) and what methods I used to reach those findings. You should, if you want to, be able to go get your own lenses and testing equipment and duplicate those findings. And maybe you can give us some input that helps us refine our methods. That's how science works.

I could just pat you on the head, blow some smoke up your backside, call my methods proprietary and too complex, and tell you this lens scores 3.75 and that lens scores 5.21, so you should run out and buy that. That provides hours of enjoyment fueling fanboy duels on various forums, but otherwise is patronizing and meaningless. Numbers given that way are as valid as the number of the Holy Hand Grenade of Antioch.

 Methods

All lenses were prescreened using our standard optical testing to make certain the copies tested were not grossly decentered or tilted. Lenses were then measured at 10, 20 ,30, 40, and 50 line pairs per mm using our Trioptics Imagemaster MTF bench. Measurements were taken at 20 points from one edge to the other and repeated at 4 different rotations (0, 45, 90, and 135 degrees), giving us a complete picture of the lens.

 

The 4 rotation values were then averaged for each copy, giving as a graph like this for each copy.

 

The averages for 10 copies of the same lens model were then averaged, giving us an average MTF curve for the 10 copies of that lens. This is the type of MTF reading we show you in a blog post. The graphics are a bit different than we've been using, but that's because we're generating these with one of Brandon's scripts now, so they'll be more reproducible now.

Graph 1: Average MTF of 10 copies of a lens.

 

Graphing the Variation Between Copies

Every copy of the lens is slightly different than this 'average' MTF and we want to give you some idea of how much variance exists between copies. A simple way is to calculate the standard deviation at each image height. Below is a graph showing the average value as lines, with the shaded area representing 1.5 standard deviations above and below the average. In theory, (the theory doesn't completely apply here, but it gives us a reasonable rule of thumb) MTF results for 98% of all copies of this lens would fall within the shaded areas.

 

Graph 2: Average MTF (lines) +/- 1.5 S. D. (area)

 

Obviously, these area graphs overlap so much that it's difficult to tell where the areas start and stop. We could change to 1 or even 0.5 standard deviations and make things look better. That would work fine for the lens we used in this example, but this is actually a lens with fairly low variation. Some other lenses vary so much that they would just make a graph that basically is nothing but completely overlapping colors, even if we showed +/- one standard deviation.

The problem of displaying lens variation is one we've struggled with for years; most variation for most lenses just won't fit in the standard MTF scale.  We have chosen to scale the variance chart by adding 1.0 to the 10lp/mm value, 0.9 to the 20 lp/mm value, 0.75 to 30lp/mm, 0.4 to 40lp/mm, and 0.15 to 50lp/mm.  We chose those numbers simply because they make the graphs readable for a "typical" lens.

Graph 3 presents the same information as Graph 2 above, but with the axis expanded as we described to make the variation more readable.

Graph 3: Average MTF (lines) +/- 1.5 S. D. (area); modified vertical axis

 

You could do some math in your head and still get the MTF numbers off of the new graph, but we will, of course, still present average MTF data in the normal way. This graph will only be used to illustrate variance. It can be quite useful, though. For example, the figure below compares the graph for the lens we've been looking at on the left, and a different lens on the right.

 

 

 

Some things are very obvious at a glance. The second lens clearly has lower MTF than the first lens. It also has a larger variation between samples, especially as you go further away from the center (center is the left side of the horizontal axis). In the outer 1/3 of the lens, in particular, the variation is extremely large. This agrees with what we see in real life: the second lens is one of those lenses that every copy seems to have at least one bad corner, and some more than one bad corner. Also if you look at the black and red  areas at the center of each lens (the left side of each graph) even the center of the second lens has a lot of variation between copies. Those are the 10 and 20 line pairs per mm graphs and these differences between copies in the center are the kind of thing that most photographers would notice as a 'soft' or 'sharp' copy.

The Variation Number

The graphs are very useful to compare two or three different lenses, but we intend to compare variation for a lot of different lenses. With that in mind we thought a numeric 'variation number' would be a nice thing to generate. A table of numbers certainly provides a nice, quick summary that would be useful for comparing dozens of different lenses.

As a rule, I hate when someone 'scores' a lens or camera and tries to sum up 674 different subjective things by saying 'this one rates 6.4353 and this one rates 7.1263'. I double-secret hate it when they use 'special proprietary formulas you wouldn't understand' to generate that number. But this number is only describing one thing: copy-to-copy variation. So I think if we show you exactly how we generate the number then 98% of you will understand it and take it for what it is, a quick summary. It's not going to replace the graphs, but may help you decide which graphs you want to look at more carefully.

(<Geek on>)

It's a fairly straightforward process to find the number of standard deviations needed to satisfy some absolute limits, for example, +/-12.5%. Just using the absolute standard deviation number though, would penalize lenses with high MTF. If the absolute MTF is 0.1, there's not much room to go up or down while if it's 0.6, there's lots of room to change. This meant bad lenses would seem to have low variation scores while good lenses would have higher scores. So we made the Variation number relative to the lens' measured MTF, rather than an absolute variation. We simulated the score for lenses of increasingly high resolution and saw the score would rise exponentially, so we take the square root of it to make it close to linear.

Initially we thought we'd just find the worst area of variability for each lens, but we realized some lenses have low variation across most of the image plane and then vary dramatically in the last mm or two. Using the worst location made these lenses seem worse than lenses that varied a fair amount in the center. So we decided to average the lens' MTF across the entire image plane. To keep the math reasonable, we calculated the number just for the 30 line pair per mm (green area in the graphs) variance, since that is closest to the Nyquist frequency of 24MP-class full-frame sensors. Not to mention, higher frequencies tend to have massive variation in many lenses, while lower frequencies have less variation; 30lp/mm provides a good balance.  Since some lenses have more variation in the tangential plane and others the sagittal, we pick the worse of the two image planes to generate the variance number.

Finally we scale the score to get a reasonable scale.

For those who speak computer better than we can explain the formula in words, here's the exact Matlab code we use:

T3Mean = mean(MultiCopyTan30);
S3Mean = mean(MultiCopySag30);
Tan30SD_Average = mean(MultiCopySDTan30);
Sag30SD_Average = mean(MultiCopySDSag30);
ScoreScale = 9;
if T3Mean > S3Mean
 TarNum = 0.125*T3Mean;
else
 TarNum = 0.125*S3Mean;
end
if Tan30SD_Average > Sag30SD_Average
 ScoreTarget = TarNum*T3Mean;
 VarianceScore = ScoreTarget/Tan30SD_Average;
 MTFAdjustment = 1 - (T3Mean/(0.25*ScoreScale));
 VarianceScore = sqrt(VarianceScore*MTFAdjustment);
else
 ScoreTarget = TarNum*S3Mean;
 VarianceScore = ScoreTarget/Sag30SD_Average;
 MTFAdjustment = 1 - (S3Mean/(0.25*ScoreScale));
 VarianceScore = sqrt(VarianceScore*MTFAdjustment);
end
VarianceNumber = VarianceScore*ScoreScale;

(</Geek off)

Here are some basics about the variance number --

  1. A high score means there is little variation between copies. If a lens has a variance number of over 7, all copies are pretty similar. If it has a number less than 4, there's a lot of difference between copies.  Most lenses are somewhere in between.
  2. A difference of "0.5" between two lenses seems to agree with our experience testing thousands of lenses. A lens with a variability score of 4 is noticeably more variable than a lens scoring 5, and if we check carefully is a bit more variable than one scoring 4.5
  3. A difference of about 0.3 is mathematically significant between lenses of similar resolution across the frame.
  4. Ten copies of each lens is the most we have the resources to do right now. That's not enough to do rigid statistical analysis, but it does give us a reasonable idea. In testing 10 copies of nearly 50 different lenses so far, the variation number changes very little between 5 and 10 copies and really doesn't change much at all after 10 copies. Below is an example of how the variance number changes as we did a run of 15 copies of a lens.
How the variance number changed as we tested more copies of a given lens. For most lenses, the number was pretty accurate by 5 copies and changed by only 0.1 or so as more copies were added to the average. 

Some Example Results

The main purpose of this post is to explain what we're doing, but I wanted to include an example just to show you what to expect. Here are the results for all of the 24mm f/1.4 lenses you can currently buy for an EF or F mount camera.

First, let's look at the MTF graphs for these lenses. I won't make any major comments about the MTF of the various lenses, other than to say the Sigma is slightly the best and the Rokinon much worse than the others.

 

 

Now lets look at the copy-to-copy variation for the same for lenses. The graphs below also include the Variation Number for each lens, in bold type at the bottom.

 

Just looking at the variation number, the Canon 24mm f/1.4L lens has less copy-to-copy variation than the other 24mm f/1.4 lenses. The Rokinon has the most variation.

The Nikon and Sigma lenses show an interesting point. Looking at the graphs the Sigma clearly has more variation, but the Sigma variation number is only slightly different than the Nikon number.  That's because the average resolution of the Sigma is also quite a bit higher at 30lp/mm  and the formula we use considers that.  If you look at the green variation areas you can see that the weaker Sigma copies will still be as good as the better Nikon copies. But this is a good example of how the number, while simpler to look at, doesn't give the whole picture.

The graphs show something else that is more important than the simple difference in variation number. The Sigma lens tends to vary much more in the center of the image (left side of the graph) and the variation includes the low frequency 10 and 20 line pairs per mm areas (black and red). The Rokinon tends to vary extremely in the edges and corners (right side of the graph). In the practical world, a photographer carefully comparing several copies of the Sigma would be more likely to notice a slight difference in overall sharpness between the lenses. The same person doing careful testing on several copies of the Rokinon would probably find each lens has a soft corner or two soft corners.

Attention Fanboys: Don't use this one lens example and start making claims about this brand or that brand. We'll be showing you in future posts that at other focal lengths things are very different. Canon L lenses don't always have the least amount of copy-to-copy variation. Sigma Art lenses in other focal lengths do quite a bit better than this.  We specifically chose 24mm f/1.4 lenses for this example because they are complicated and are very difficult to assemble consistently.

And just for a teaser of things to come, I'll give you one graph that I think you'll find interesting, not because it's surprising, but because it verifies something most of us already know. The graph below is simply a chart of variation number of many lenses, sorted by focal length. The lens names are removed because I'm not going to start fanboy wars without giving more complete information. And that will have to wait a week or two because I'll be out of town next week. But the graph does show that wider-angle lenses tend to have more copy-to-copy variation (lower variation number), while longer focal lengths, up to 100mm, tend to have less variation. At most focal lengths, though, there are some lenses that have little, and some lenses that have a lot of copy-to-copy variation.

 

 

What Are We Going to Do with This?

Fairly soon, we will have this testing done for all wide-angle and standard range prime lenses we carry and can test. (It will be a while before we can test Sony e-mount lenses - we have to make some modifications to our optical bench because of Sony's electromagnetic focusing.) By the end of August, we expect to have somewhere north of 75 different models tested and scored. It will be useful when you're considering purchasing a given lens and want to know how different your copy is likely to be than the one you read the review of. But I think there will be some interesting general questions, too.

  • Do some brands have more variation than other brands?
  • Do more expensive lenses really have less variance than less expensive ones?
  • Do lenses designed 20 years ago have more variance than newer lenses? Or do newer, more complex designs have more variance?
  • Do lenses with image stabilization have more variance than lenses that don't?

Before you start guessing in the comments, I should tell you we've completed enough testing that I've got pretty good ideas of what these answers will be. And no, I'm not going to share until we have all the data collected and tabulated. But we'll certainly have that done in a couple of weeks.

 

Roger Cicala, Aaron Closz, and Brandon Dube

Lensrentals.com

June, 2015

A Request:

Please, please don't send me a thousand emails asking about this lens or that. This project is moving as fast as I can move it. But I have to 'borrow' a $200,000 machine for hours to days to test each lens, I have a busy repair department to run, and I'm trying to not write every single weekend. This blog is my hobby, not my livelihood, and I can't drop everything to test your favorite lens tomorrow.

Canon 5Ds Teardown

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When Lensrentals.com first got the first Canon 5Ds and 5D sr cameras in stock, Aaron and I immediately started screaming that we wanted to take one apart. It turns out we received enough 5Ds cameras to let us have a day with one to do just that. Of course, we don't expect to find out anything amazing and revealing. We expect it will look pretty much like the Canon 5DIII and 7DII on the inside. But hey, you never know. Plus we'll be repairing these soon enough, so we might as well find our way around now.

If you want to do some comparisons yourself, you can compare this to our Canon 5D III teardown and Canon 7D II teardown. Or if you'd rather follow along from home with your own 5Ds go grab your screwdrivers and let's get started!

From the outside looking in, there's not a lot of difference in appearance from the 5D Mk III.

 

All photographs Roger Cicala, Lensrentals.com, 2015

 

 

All photographs Roger Cicala, Lensrentals.com, 2015

 

The side panel covering the I/O ports comes off first.

All photographs Roger Cicala, Lensrentals.com, 2015

 

Looking into the camera we see a welcome sight. There are robust metal plates and screws holding the port assembly very firmly. Anyone who has had an HDMI or other port pull off the circuit board when a connected cable gets tugged too hard will appreciate this.

All photographs Roger Cicala, Lensrentals.com, 2015

 

The bottom plate is removed next.

All photographs Roger Cicala, Lensrentals.com, 2015

 

The tripod base is now exposed. It is supposed to be more robust than previous 5D cameras but we can't tell a lot from here, although there do seem to be more screws holding it to the chassis than with the 5D Mk III.

All photographs Roger Cicala, Lensrentals.com, 2015

 

The back cover assembly removes in an identical manner to the 5D Mk III.

All photographs Roger Cicala, Lensrentals.com, 2015

 

There is a slightly different connector from the back assembly to the PCB.

All photographs Roger Cicala, Lensrentals.com, 2015

 

And the back panel assembly has only minor differences from the 5D III. One worth noting is the aluminum LCD backing plate is stronger with some stamped strengthening areas pressed into it. In previous 5D cameras the LCD could be pressed down into the camera pretty easily because the backing plate was pretty thin.

All photographs Roger Cicala, Lensrentals.com, 2015

 

Internally, the camera looks a little different because the PCB is partly covered with a thick, plastic adhesive sheet rather than the thin sticky-taped vinyl we usually see.

All photographs Roger Cicala, Lensrentals.com, 2015

 

This is the material used in the 7DII, and is a lot easier to work with than the 5DIII's flimsy vinyl tape. It doesn't make a bit of difference to anyone who doesn't repair cameras, but I do repair cameras and so I was pleased. This is much easier to peel up without tearing.

All photographs Roger Cicala, Lensrentals.com, 2015

 

The electrical shields are removed easily.

All photographs Roger Cicala, Lensrentals.com, 2015

 

And now the PCB and most of the camera's chips are exposed.

All photographs Roger Cicala, Lensrentals.com, 2015

 

Unhooking a LOT of flexes and taking out a few screws lets us remove the PCB. One thing you probably didn't notice, but that made us weep with joy: the I/O ports are NOT soldered to the PCB. They are on a separate board that we'll show you later. This is a big thing, because now if you pull one of the I/O loose, it no longer means a PCB replacement is necessary.

All photographs Roger Cicala, Lensrentals.com, 2015

 

For you chip hunters, here's the PCB out of the camera.

All photographs Roger Cicala, Lensrentals.com, 2015

 

Looking beneath the PCB in the camera body, we can see the sensor's circuit board in the center and the CF card assembly over on the right.

All photographs Roger Cicala, Lensrentals.com, 2015

 

Next step in stripping the camera is removing the front plate, which is quite straightforward.

All photographs Roger Cicala, Lensrentals.com, 2015

 

With the front, sides, bottom and back removed, there's only one more screw left before we can remove the top plate.

All photographs Roger Cicala, Lensrentals.com, 2015

 

The top plate itself isn't much different than what we've seen in numerous other Canon DSLRs.

All photographs Roger Cicala, Lensrentals.com, 2015

 

And finally the bottom tripod mounting plate was removed.

All photographs Roger Cicala, Lensrentals.com, 2015

 

We had been told the tripod plate was more robust than in the 5DIII, and that certainly is true. It's mounted to numerous chassis points with a total of 8 very long screws. I don't usually show pictures of screws, but theses are serious things, way longer than what we are used to seeing mount tripod plates to cameras. And while a camera breaking at the tripod mount is untypical, it's nice to see that these cameras are getting more and more robust.

All photographs Roger Cicala, Lensrentals.com, 2015

 

The side view shows the metal in the plate is thicker than we're used to seeing, too.

All photographs Roger Cicala, Lensrentals.com, 2015

 

Finally we took off the memory card door. It didn't have to wait until last, but we like to do it that way because of the door-shut sensor underneath; it's easy to break and breaking it results in major problems.

All photographs Roger Cicala, Lensrentals.com, 2015

 

Here is the paper-thin door shut sensor, which fits through a little slot in the memory card door. Bend it and the camera thinks the door is open and won't power on.

All photographs Roger Cicala, Lensrentals.com, 2015

 

With all the external covers and cases off we can take a look around the insides of the camera a bit. The overall front view gives a nice look at the pentaprism up on top showing you just why SLRs all have that hump in the middle. On the left is the battery housing PCB and battery housing.

All photographs Roger Cicala, Lensrentals.com, 2015

 

One thing we weren't thrilled about is the plastic lever on the metal lens-release-locking pin. It may be just fine, probably is just fine. But my inner-paranoid repair guy comes out and thinks 'if that plastic lever comes loose from the pin, a lens is locked on to the camera body'.

All photographs Roger Cicala, Lensrentals.com, 2015

 

Going underneath the camera, we can get a good look at the AF sensor. Well, not the sensor itself, the housing of the AF sensor (red arrow). The housing is black and difficult to see, but you can see some white marks it. Also note the adjustment screws and the thick glue used to keep it locked in place after it was adjusted at the factory.

All photographs Roger Cicala, Lensrentals.com, 2015

 

While we're looking around, I should probably mention weather sealing because many of you are fascinated by it. Canon presents the 5Ds and 5D sr as studio cameras and the weather sealing clearly isn't as robust as that we saw in the 7D Mk II, but it's still pretty good, particularly around the doors. You can see foamed sealing around the memory card door in an earlier image. There's similar sealing around the battery door on both sides. We didn't see any rubber gaskets around the top assembly, rear assembly, etc.

All photographs Roger Cicala, Lensrentals.com, 2015

 

All photographs Roger Cicala, Lensrentals.com, 2015

 

The bottom line is this is standard weather sealing. Would I take it out in the rain? Hell no. But I wouldn't take any other camera out in the rain without plastic bags over everything, either. I don't trust 'weather sealing' and neither do the manufacturers. Otherwise their warranty would cover water damage, and it doesn't.

We also wanted to take a closer look at the I/O ports on this camera. Most of you have probably never had a problem with this, but having to replace a PCB because an I/O port has been yanked off is becoming more and more common as people attach more external devices to their cameras.

I'm most impressed by Canon's approach to this. The ports are all on a separate board, connected by wires to the main PCB. So a broken I/O port means simply replacing this board.

All photographs Roger Cicala, Lensrentals.com, 2015

The removal shows just how seriously Canon has planned this out. The board is strongly braced directly to the camera chassis at several places, so the ports are much less likely to bend and tear off in the first place. If you look back at our 7D Mk II teardown you can see the I/O ports were strengthened and partially moved off of the PCB; the 5Ds cameras improve this even further.

All photographs Roger Cicala, Lensrentals.com, 2015

 

As an aside, removing the I/O assembly, its covering tapes, and the metal shield uncovers the four Analog Devices A/D converters.

All photographs Roger Cicala, Lensrentals.com, 2015

 

We did take out the CF card assembly, which is thankfully on a separate board. (Some cameras solder this to the PCB, too, so when a pin is bent or broken a PCB replacement may be needed.) The SD card slot is soldered to the back of the PCB, but SD card slots are far less likely to break than CF slots are.

All photographs Roger Cicala, Lensrentals.com, 2015

 

With everything removed we could get a glimpse at the edges of the image sensor around its circuit board (the green board in the center of the image above).

All photographs Roger Cicala, Lensrentals.com, 2015

 

Taking the image sensor and mirror box out will have to wait for another day, I'm afraid. Stock is still short and this camera had to be reassembled, tested, and shipped out today. Removing the sensor-mirror box assembly might have put things out of alignment and while we are gutsy, we aren't dumb enough to be certain we could have gotten that all corrected in another hour or two.

Summary

Outside of the stuff we already know about the new Canon cameras, there were not many surprises looking inside, and the few surprises we had were positive. There was Canon's usual very clean design and layout. There were incremental improvements in the engineering, like the separated I/O system, more robust tripod mount assembly, and improved inner tapes and shields. I have a little concern about the lens release pin, but it probably will not be an issue. After all, I'm known to be paranoid.

When we get more stock and demand slows down we'll pull the sensor out of one for closer examination, but that will have to wait a month or two.

 

Roger Cicala and Aaron Closz

Lensrentals.com

June, 2015

 

 

 

 

Canon 5DS and 5DS R Initial Resolution Tests

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Like everybody else, we're pretty excited to get our hands on Canon's new 5DS and 5DS R. There are already a lot of hands-on articles about the cameras that probably have told you more than you need to know to make your purchase decision. Of course, for most of the Canon shooters who read this blog, the purchase decision was just which place you want to buy it from.

For me, I want some lab data to see just how much of a difference those megapixels make. More particularly, I want to see how much of a difference they make when shot through a reasonably good lens, an excellent lens, and an adequate lens. Some people want to simplify things too much and claim certain lenses are 'good enough' for the new cameras and others aren't. It's not that simple.

So we begged and threw temper tantrums until Drew agreed to let us have a couple of the new cameras for a couple of days testing in our Imatest lab. That was enough time for us to get a quick overview using several different sample lenses, but it will be months before we have a good database of which lenses are most capable on the new cameras. Continue reading

We're Hiring! - Summer 2015 Open Positions

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We're growing, which means we're hiring! Lenrentals is a fantastic place to work. We believe in working hard, having fun, and giving our customers the best possible rental experience. Our team members get great benefits, including health, dental, paid vacation, and 401(k), not to mention - FREE RENTALS!

Please see below for a list of job descriptions. To apply, please send your resume to jobs@lensrentals.com

Phone calls not accepted. Continue reading

I Don't Know Why It Swallowed a Fly - Weather Sealed Lens With a Fly Inside

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I've been blogging about testing and taking apart camera equipment for almost a decade. Lensrentals.com has many thousand lenses these days, and they all get used frequently. When you have lots of lenses and they get used frequently, stuff gets inside them.

Usually the stuff that gets inside is dust. Our repair techs open up and clean dust out of more than 100 lenses a week. Not because the dust matters a bit in a photograph; it doesn't. But because people still seem to think it does. People also, for reasons I can't understand, seem to think that weather sealed lenses are less likely to get dust in them than non-weather sealed lenses. I'm not sure why they think this, but they do.

Sometimes the stuff that gets inside them is interesting and we get to blog about it. We found a spider, complete with web, inside a lens once and yesterday we got to add a new item to our 'found inside lenses' collection; a nice, fat, fly. And not just a fly inside a lens, but one way down deep inside a weather sealed lens. So deep that it took 4 hours of work to get it out.

The lens in question was a Canon 24-105mm f/4 IS that returned from rental looking quite normal with the renter taking equally normal photos.

Nothing unusual looking about this lens on its return.

Continue reading

The Space Lens Mystery Screw

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We get to do some fun things through our testing company, Olaf Optical Testing. A lot of it I can't talk about but sometimes we get a project that we can share. One of these came up recently when Matt Leeg asked us if we were interested in testing and cleaning an Angenieux 25mm f/0.95 lens that was probably a backup lens for the NASA Ranger missions sent to the moon in the 1960s. We thought about it for between 0.1 and 0.125 seconds and said, yeah, we could probably do that.

This post won't help your photography one little bit, nor will it help you with choosing your next lens, or even show you how to fix anything. But for me, it's a fascinating glimpse into some history from a period I admire -- at least from a technology and engineering standpoint. Today we whine about cameras only having 24 megapixels, lenses that only autofocus with 95% accuracy, WiFi access that only allows us to transmit a few hundred kilobits per second.

Continue reading

Tamron 15-30 f/2.8 Di VC Partial Teardown

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We've become fans of the Tamron 15-30mm f/2.8 Di VC USD lens since we first tested it optically, but we haven't really been inside of one yet. It's not that we weren't curious. We've just been trying to get through the week before and after Memorial Day, typically one of the busier times of the year for the repair department, so we haven't had time.

But we had two copies show up in the repair department with a jammed zoom mechanism. A peek under the zoom rubber didn't show any obvious problems. So we needed to open them up and see what was wrong, and thought we'd take some pictures along the way. This is a rather different looking lens and we were curious if it was different inside too.

All photos copyright Roger Cicala and Lensrentals.com, 2015

Continue reading

May 12th - Customer Service Closing Early

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On May 7th, our customer service manager, Sharon Perez, passed away unexpectedly. Sharon was a wonderful friend and co-worker for the past 4 1/2 years. She was an integral part of our Lensrentals family and she will be sorely missed by all of us.

Out of respect for our friend Sharon, and to allow her co-workers to attend her memorial service, our customer service department will be closing at 12:00 PM CT today. If you need our assistance, please call us before this time. We will have staff monitoring email throughout the afternoon but our response times will be slower than normal.

Canon Announces T6 Sensor Recall

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I want to give credit to Canon for so quickly handling the problem we first reported with some T6 sensors. We announced the problem on April 30th, and within 10 days Canon had determined which cameras were affected (those with Serial Numbers beginning with "01 or "02") and issued a product alert.

Let me add that most cameras in the affected SN range do NOT have the problem. Some cameras have a mark in the battery door that identifies them as not possibly affected.

Credit for image, Canon, USA. http://www.usa.canon.com/cusa/support/consumer?pageKeyCode=prdAdvDetail&docId=0901e02480f0bcb2

 

Even if your camera does NOT have this mark, it still probably isn't affected. If you lock up the mirror for sensor cleaning you can look and see if you have one of 'those' sensors. If you aren't sure, Canon will check for you at no cost and correct the problem without charge, although it will take them a bit of time to get a solution ramped up.

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