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If you think your copy of your lens is inferior....

 
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Mike B in OKlahoma



Joined: 04 Aug 2006
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Location: Oklahoma City

PostPosted: Wed May 09, 2007 6:42 pm    Post subject: If you think your copy of your lens is inferior.... Reply with quote

Some time ago, I got a Canon 24-105 image stabilized lens for a "walking around lens". The range seemed convenient, and I liked the idea of image stabilization, particularly if I was hand-holding. I heard rave accounts of the lens and how sharp it was, at least between about 28mm and 90mm (I've seen some claims that it softens up at longer than 90mm, and most people report that image quality deteriorates between 24-28mm.

When I got my copy, I didn't take the time to seriously test it out. When I finally did use it and take a look at the results, I was disappointed. The images it produced were mush. It was definitely soft at the wide and long ends, and not too great in the middle range. And it was too late to return it to the seller. I loved the general utility of the lens, but didn't care for the pictures if I pixel-peeped. I felt like my camera far outresolved the lens.

I've been saying for some time that I would send it to Canon and ask them to see if they could adjust the lens and improve the image quality. I kept putting it off, but I finally got around to it. I'm MUCH more pleased with the lens now. I haven't done rigorous tests, but in some fairly controlled tests shooting outdoors at landscape distances, I find it is sharper than my 16-35 zoom from about 28mm and longer, and it stays very acceptably sharp all the way up to 105mm. It also is still pretty sharp wide open, though it gives up a little bit compared to f/8. It gets very soft at f/16 and stopped down more.

Canon repaired the lens under warranty. They claimed the lens rear-focused, and that they made unspecified electrical repairs to the lens.

It's not awesome--My $75 50/1.8 prime is sharper and crisper than the zoom. But I'm much happier with it now! And the repair was under warranty, so it cost me only the shipping to Canon.

The point of this post: If you have a lens you feel doesn't perform as well as you think it should, it definitely may be worthwhile to send it to the manufacturer, even if you are out of warranty. Certainly paid off for me!

A couple of minor points: The 24-105 focuses reasonably close, and I've been intending to try slapping my Canon 500D closeup diopter on it to see how it would do for emergency closeup use. Haven't tried it out yet, though! Also, if you have this lens, turn off the IS when using it on a tripod. Canon claims the IS is not tripod-sensitive, but I find a substantial decrease in image quality if I leave the IS on while on tripod. When handholding, the IS works very well.
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Mike Broderick
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Ken Ramos



Joined: 27 Jul 2006
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PostPosted: Wed May 09, 2007 7:27 pm    Post subject: Reply with quote

Good idea, I did not know that. Though I have had my 28 -200mm for almost a year now. It too does pretty much what you have described with your lens. However as I recall when I used to shoot 35mm. I never had a problem one with image quality from any lens I used, even the wide angle tele-zooms, at any setting. Why all of a sudden this is a problem with almost every lens you read a review on. Some folks claim good results from a lens and others bad from the same lens. Could it be someone does not know how to use the gear or is it the manufacturers of these lenses have extremely poor quality control? Seems to me we are all getting taken for a ride with this digital photography stuff, though it is quite handy and I am spoiled rotten by it. Of course that is what the manufacturers want...isn't it? Besides our money of course for inferior products. Confused Rolling Eyes

I am presently in the market for a new lens as a walk around but from all the reviews I am reading, there is nothing out there worth my hard earned money. I have been asking around about various wide angle zooms and still I am unsure when I look at what is recommended , if my "copy" (where did that come from..."copy?" I read that all the time. Laughing ) will give the same great results I read about for me? Sad Maybe I should go back to sheet film, a shoe box, and a pin hole. Laughing
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rjlittlefield
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PostPosted: Wed May 09, 2007 9:11 pm    Post subject: Reply with quote

Ken, I like your idea -- sheet film, a shoe box, and a pinhole give very reliable results. Neither the exposure time nor the absolute resolution are anything to write home about, but hey, there are tradeoffs.

Regarding the larger issue, I think a big part is just focus -- as if it makes sense to talk about "just" focus!

Lens design and sensor resolution seems to have outstripped optical viewfinders. With most cameras, you simply cannot tell when the image is critically focused, by looking through the viewfinder.

In one of my recent experiments, I discovered that even using an 8X viewfinder magnifier, I could only tell that focus was "good", not necessarily "perfect".

In that case, I solved the problem by shooting a bunch of frames, tweaking focus, and picking the best one.

Unfortunately, in most cases that option is not available. So what do you do?

Answer: let the camera and lens detect and report best focus.

It's a brilliant idea, when it works right. Too bad it doesn't work right all the time.

I wish I knew a solution, but I don't. For stacking, it's a non-issue -- just shoot a deep enough stack. For most macro work, it's also a non-issue -- critical focus turns into focus placement, and we all know that's a crapshoot because of camera & subject movement. For lower mag closeups and scenics, yep, it's important, and Mike's solution is the best I know -- if it seems wrong, complain!

--Rik
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twebster
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PostPosted: Thu May 10, 2007 1:46 am    Post subject: Reply with quote

Hi ya' Mike and Ken,

Ken in my experience, every manufacturer makes a lemon now and then. I've had manual focus lenses (Nikon) that had to be sent back because they would not focus properly at infinity. I've had to send a couple of Canon autofocus bodies in for adjustment. The thing is, every manufacturer occasionally puts out a lemon, or maybe the lens/camera got bounced once too many times in shipment, nevertheless, you hear more about the lemons than you hear about the equipment that works propely right out of the box. More often than not, the equipment does work properly. Very Happy

For all of the electronic gadgetry that is involved with autofocus and the manufacture of dSLRs and lenses, I am surprised that there isn't a higher failure rate. Your sending the subpar lens back to Canon, Mike, is right on the money. I took 2 weeks off from shooting and sent 3 bodies and 5 lenses to Canon Service and had the whole lot of them calibrated! Canon Service did it all under warranty for the new equipment and the 1 out of warranty lens was calibrated for free!

Also, I'm not surprised that your 50mm f 1.8 lens is sharper than the 24-105 zoom, Mike. The 50mm is a highly regarded prime focal length lens with a long history of development and refinement. The 24-105 zoom lens is a good lens in its own rights but very seldom do zoom lenses match the performance of a good prime focal length lens.

As regards the IS on a tripod, if you are using an electronic release to fire the shutter with the camera/lens mounted on a tripod, the IS is useless and will cause sharpness issues. The IS, however, should work fine if you are gripping the camera/lens and firing the shutter manually while the camera/lens is tripod mounted. That's a little something I don't think is addressed in the instruction book. Wink

Best regards to all, Very Happy
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Ken Ramos



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PostPosted: Thu May 10, 2007 2:44 am    Post subject: Reply with quote

Well Mikes information is greatly appreciated Very Happy , I did not know Canon would be so user friendly, thanks Mike . I am going to send my 28-200mm back for cal. Hopefully I will have a reasonably good lens when it returns. Very Happy However what still bugs me is why wasn't this thing right the first time, just how many lemons can one company make at a time? I agree it is much easier to complain about something that does not work right the first time than it is to comment on something that does. Rolling Eyes
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twebster
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PostPosted: Thu May 10, 2007 10:15 am    Post subject: Reply with quote

Ken Ramos wrote:
...However what still bugs me is why wasn't this thing right the first time, just how many lemons can one company make at a time? I agree it is much easier to complain about something that does not work right the first time than it is to comment on something that does. Rolling Eyes


Hi ya' Ken. Zoom lenses with a zoom range greater than 3:1 present a whole slew of design challenges and compromises. Your 28-200 zoom most likely was "right the first time" but may have been handled roughly in shipment and some elements knocked out of alignment in the process. Also, because of the wide range of zoom, this may be the best performance of which this lens is capable. Rarely do zoom lenses with a greater than 3:1 zoom range perform to expectations. However, lens manufacturers produce these lenses to meet the demands of the consumer for lighter weight, "do all" lenses. In my experience, there's just no such thing.

I think we don't realize just how complicated zoom lenses are to design and manufacture. There are many more internal lens elements that must be placed in precise positions within the lens barrel for the lens to retain any semblence of optical performance than there are compared to prime focal length lenses or zoom lenses of 3:1 range or less. This, then, requires correspondingly more complex zooming cams. For manufacturers to make a profit high enough to justify the design and manufacturing costs of such lenses, much of the manufacturing needs to be a hands-off, robotic process. This, in itself, invites some variability in manufacturing accuracy. There are many more stages in the manufacture of long zoom range lenses that invites variations in quality.

The only real way to know if a lens is performing poorly due to simple misalignments or a flawed lens design is to send the lens back to the manufacturer for calibration. If the lens, once returned, performs better than before, that's good. If a lens' performance is no different after calibration then the issue is most likely an optical formula that cannot deliver adequate lens performance over the given zoom range.

I think, too, that photographers have to realistically re-examine their expectations of how a long range zoom lens is to perform. If their primary expectation is high optical quality, they are better off with zoom lenses with more limited ranges or are better off with the use of a number of prime focal lengths that cover the range of focal lengths they desire. If their primary expectation is one of convenience, then photographers need to accept whatever optical performance they receive from a long range zoom lens. It is nearly impossible to incorporate both high optical performance and a long zoom range in a single lens. Canon probably comes closest with the 28-300mm f 3.5-5.6L IS USM zoom lens. However, the cost (over $2,000US) and the weight (3.7 lbs) puts off most buyers. Also, the minimum focus distance for this lens (2.3') is terribly restricting at the wide end of the zoom.

What is considered a high rate of returns due to improper alignment or other manufacturing issues? One out of ten? One out of one hundred? One out of five hundred? My guess it is more like 1 out of 500. Also, you read many of the gripes about poor lens QA but, if the truth were told, many times it is not the fault of the lens but it is more the fault of the autofocus mechanism in the camera. You don't very often read how a photographer, disappointed with a lens, has actually found the fault lies with the camera and not the lens.

IMO, camera manufacturers do a stellar job in manufacturing complex pieces of electro-mechanical equipment and, at the same time, keep costs down so that much of this equipment remains affordable.

Best regards as always, my friend Exclamation Very Happy
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beetleman



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PostPosted: Thu May 10, 2007 10:39 am    Post subject: Reply with quote

Mike Said:
Quote:
Also, if you have this lens, turn off the IS when using it on a tripod. Canon claims the IS is not tripod-sensitive, but I find a substantial decrease in image quality if I leave the IS on while on tripod. When handholding, the IS works very well.

This post has got me thinking. My camera has IS built in. I always leave it on even on the tripod for stacks. Lately, I have been getting, what I think are softer images than usual. The orgional review on the camera did say the images were a little soft compared to the other cameras in its` price range anyway. I wonder if the IS is getting old? I will have to try and shoot with the IS off and see if I get anything different Think
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twebster
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PostPosted: Thu May 10, 2007 11:04 am    Post subject: Reply with quote

beetleman wrote:
Mike Said:
Quote:
Also, if you have this lens, turn off the IS when using it on a tripod. Canon claims the IS is not tripod-sensitive, but I find a substantial decrease in image quality if I leave the IS on while on tripod. When handholding, the IS works very well.

This post has got me thinking. My camera has IS built in. I always leave it on even on the tripod for stacks. Lately, I have been getting, what I think are softer images than usual. The orgional review on the camera did say the images were a little soft compared to the other cameras in its` price range anyway. I wonder if the IS is getting old? I will have to try and shoot with the IS off and see if I get anything different Think


Doug, the IS in the Canon Powershot series of cameras was never intended to be turned on while the camera is tripod mounted. The lack of vibration when the camera is tripod mounted causes a destructive feedback loop that can actually cause image vibration due to the lens element controlled by miniature gyros. For best results, if you mount the camera on a tripod, turn off the IS. In my experience, IS doesn't "wear out". It either works or fails. Sad
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beetleman



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PostPosted: Thu May 10, 2007 1:32 pm    Post subject: Reply with quote

Thanks Tom for the feedback...always a ton of great info when you guys get together and talk things over.
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Mike B in OKlahoma



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PostPosted: Thu May 10, 2007 3:30 pm    Post subject: Reply with quote

twebster wrote:

Also, I'm not surprised that your 50mm f 1.8 lens is sharper than the 24-105 zoom, Mike. The 50mm is a highly regarded prime focal length lens with a long history of development and refinement. The 24-105 zoom lens is a good lens in its own rights but very seldom do zoom lenses match the performance of a good prime focal length lens.


Understood, especially in the case of a 4:1 ratio zoom that has to incorporate both wide-angle and telephoto. Plus, a normal lens is apparently a pretty easy-to-design lens from an optical perspective. So I'm not unhappy about this. Some writers, especially Michael Reichmann, claim that modern zooms are just as good as primes, at least when both are stopped down. That's not my experience with normal zooms at all. The 28-70L that I replaced with a 24-105 wasn't as sharp as my 50/1.8. Canon has done a good job with the 24-105, it is as sharp as the 28-70 was, despite having a larger zoom ratio.

For telephoto zooms, I do find that my 70-200/4 lens is actually a bit sharper than my 135/2.8 prime (admittedly not a first-string Canon lens) or my 180mm macro (which _IS_ a first-string Canon lens. And I can tell little or no difference in my 100-400L and the same two primes. My 300/2.8 outshines them all in sharpness and clarity, however!
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Mike Broderick
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Mike B in OKlahoma



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PostPosted: Thu May 10, 2007 3:35 pm    Post subject: Reply with quote

[quote="twebster"]
beetleman wrote:
For best results, if you mount the camera on a tripod, turn off the IS. In my experience, IS doesn't "wear out". It either works or fails. Sad


What Tom said! The IS on all the Canon point-and-shoots that I'm aware of, and on their older telephoto lenses, is not designed for tripod use. In addition to lowering image quality, it needlessly runs down your battery! I suspect you'll do better with the IS turned off on your S1. If you have a shakey tripod, or the ballhead is loose for maneuvering, the IS _MIGHT_ help. My 100-400 lens has IS which Canon says will not work on a tripod. In practice, if I'm shooting wildlife with the ballhead loose, having IS engaged often helps. Once in a great while, it starts getting crazy and making a mild knocking sound, in which case I turn off the camera for a minute and start again. But unless you confirm through experience that using the IS on a loose head (If you ever shoot that way) is useful, I'd turn the IS off as Tom indicated.
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Mike Broderick
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Mike B in OKlahoma



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PostPosted: Thu May 10, 2007 3:39 pm    Post subject: Reply with quote

Ken Ramos wrote:
Well Mikes information is greatly appreciated Very Happy , I did not know Canon would be so user friendly, thanks Mike . I am going to send my 28-200mm back for cal.


Ken, I'd send it in soon--You mentioned that the lens was about a year old. If you send it in during the warranty period (I'm pretty sure that is one year) Canon will definitely not charge you unless they find that the problem was due to dropping the lens or similar not-their-fault misfortune. Outside the warranty period, they might or might not charge you, depending on how good a mood the service person is in. So get it in quick!
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Mike Broderick
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DaveW



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PostPosted: Fri May 11, 2007 8:44 am    Post subject: Reply with quote

The first version of Nikon's VR (Vibration Reduction System) could not be used on a tripod, but they claim their new version can.

Many lenses that produced great images on film are now not good enough for the APS sized sensors. I don't know whether is is the sensor resolution is too good for them, or if it is just that being smaller to start with the image will be enlarged more for any given print size.

I was also reading a lens review the other day on a zoom and the tester made the remark the lens was actually a vari-focal rather than a zoom, like many new autofocus lenses. The vari-focal preceded the zoom and required re-focusing every time you altered the focal length by zooming.

A true zoom once focused on an object should retain sharp focus on it throughout it's zooming range. It seems because most people now permanently use autofocus some manufacturers are not producing the more expensive true zooms but vari-focals and letting autofocus take care of any slight focus shift whilst zooming. If you use them on manual however you may need to adjust focus after zooming.

I don't know if it is true of the camera industry, but expect it is. Most manufacturing industry is now going over to batch testing rather than testing every individual item. With batch testing you only test one in say a dozen to see if they are coming off the machines or assembly lines OK. That means the odd bad one can creep through that would in the past have been weeded out with individual testing.

DaveW
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Mike B in OKlahoma



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PostPosted: Fri May 11, 2007 4:17 pm    Post subject: Reply with quote

DaveW wrote:

Many lenses that produced great images on film are now not good enough for the APS sized sensors. I don't know whether is is the sensor resolution is too good for them, or if it is just that being smaller to start with the image will be enlarged more for any given print size.


Another problem, particularly with wide-angle lenses designed for film, is that some lenses are designed so that the light hits the film (or sensor) surface at a sharp angle, rather than perpendicularly. With film, this made no difference, as the film reacted to a given photon the same way no matter what direction the photon came from.

With digital, the way the sensor (actually the individual pixel) reacts is more dependent on the angle the light is coming in at. Light coming in at sharp angles may not be detected or may affect the pixel in an unexpected way. I understand that manufacturers have even done things like put small lenses over each pixel to help redirect incoming light to the right angle in an attempt to compensate for this.

These effects help explain why some digital camera models do very well with a given lens, and others that you'd expect to produce similar quality do not do well.
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Mike Broderick
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DaveW



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PostPosted: Sat May 12, 2007 1:38 am    Post subject: Reply with quote

The problem with digital v. film when it comes to off axis rays hitting the sensor is that film is a flat surface whilst the light sensitive pixels are at the bottom of tiny pits, with as you say now tiny lenses on top to try and redirect the light downwards.

It is similar to water at the bottom of a well. If you shine a light vertically downwards the water at the bottom is illuminated but if you stand back at a slight angle to the well the light hits the side of the well not the water at the bottom, or at best only partly illuminates it. This is the cause of vignetting at the edges of some images, particularly with wider angle lenses.

It is also the cause of the vignetting problems Canon has had with it's full frame 35mm sensor in it's professional cameras when using lenses designed for the 35mm film format. This is one of the major reasons Nikon has not introduced a full frame sensor on it's professional cameras because users wish to still use their old 35mm film lenses without these vignetting problems. Correcting vignetting in post processing is really only a crude fix to get over the problem.

I gather the problem can be partially solved with a collimating lens as the rear element of lenses but for full frame digital what is really required is a whole new range of lenses with a wider covering circle so off axis rays are more vertical to the sensor. That means larger and more expensive lenses for any given focal length.

There are rumours Nikon has been experimenting with a curved or dished sensor shaped rather like the retina of the human eye to overcome the problem of existing 35mm film lenses on full frame digital, because this would mean off axis rays would strike the outer pixels more vertically, that is how the human retina has evolved to solve the problem. However many dismiss this curved sensor idea as just speculation because it would be dear to manufacture and the APS sized sensor already provides more than adequate image quality with existing film lenses.

DaveW
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