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Teleconverter Comparison: Tamron 01F vs. Vivitar Macro
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PostPosted: Tue May 10, 2011 4:44 am    Post subject: Reply with quote
Differences on crop sensor are probably less than on full-frame. Maybe a lot less. Wink


PostPosted: Tue May 10, 2011 5:04 am    Post subject: Reply with quote
Yes, I'm sure full frame tests will show things like resolution falloff in the corners that a crop-sensor camera won't. Maybe one of these days when I get a 5D Mk II I can do the tests properly. Or else shoot all these tests using film.


PostPosted: Thu May 12, 2011 7:11 pm    Post subject: Reply with quote
Michael,

I've been busy at work, so I am only just getting around to looking at your tests.

cooltouch wrote:
So, once again, I must respectfully disagree with Mark's analysis.


Please feel free to disagree. There is no harm in friendly discussion. In fact, it is now clear to me that we are comparing apples and oranges. You are looking at the case when the lens is the limiting factor, whilst I am looking at the case when the camera is the limiting factor. Naturally, therefore, our conclusions are different.

In the case when the lens is limiting the resolution, adding a TC should give exactly the same image but at twice the size. As long as the image with the TC really is the image without doubled, it can be said the TC has had no adverse effect on the image. Of course, it has had no beneficial effect either, so why bother using it?

In the case where the camera is limiting the resolution, the TC increases the size of the image and allows the sensor to record more detail. The amount of extra detail that is revealed depends on the amount of detail in the subject, the quality of the lens (determining the detail in the original image) and the quality of the TC (determining the quality of the magnification). This scenario is clearly relevant to telephoto photography. I like to think of my tests are answering the question:

"To what extent is a lens with a TC an alternative to a dedicated lens of double the focal length when photographing distant objects?"

In real life, what matters is the quality of the image that you can get from the Lens, TC and camera combination. Right at the start of this thread (actually the thread started by DSG), I said that I had found the TC gave no more detail than cropping and enlarging. Well, my tests with the Zuikos prove me wrong about that! Previously, I was working near the limit of "lens limited" resolution. In the test reported above, I was in the case of "sensor limited" resolution.

I will quickly respond to some of your points:

cooltouch wrote:
As I mentioned in a previous post, it is not terribly realistic to expect much difference in the amount of detail that one can extract from an image taken with a TC and a given lens, simply because the lens is the limiting factor.


As discussed above, you are correct if the lens is the limiting factor. My scenario (and tests) is when the camera (sensor) is the limiting factor, not the lens. With the lens on its own, the detail in the image cannot be recorded by the sensor. The TC is added to double the image size at the senor and so allow more detail to be recorded. My tests with my Zuikos showed this in action. The TC does give more detail. The problem being that the improvement was not as much as would be expected and accompanied by a hold load of other problems (mainly a lot of colour fringing).

cooltouch wrote:
Mark's claim that a TC is actually doing much worse because there is essentially no improvement doesn't follow either because the TC is not anything more than a doubler. In fact, his images taken with the longer lenses tend to prove this.


My point is the TC is does a poor job because the extra information it reveals, in the case when more detail is there to be revealed, is not in proportion to the increase in magnification. In my tests, the 200mm+TC clearly gave a big improvement in detail compared with the 200mm on its own at the same distance. In fact, as I noted, the discernible lines had about twice the spatial frequency and thus in this sense the TC was doubling the resolution. But the contrast across the edges was degraded by the colour fringing and so in real terms the performance is not "doubled". I base this assertion (that the contrast is degraded) on the fact that the image recorded at half the distance has very high contrast edges. It is reasonable to assert that that the MTF of the lens will not change when changing the focus distance from 13 m to 6.5 m. Thus, if I had a detector capable of recording unlimited detail, I'm asserting that it should have been able to record an image at 13 m exactly like the one recorded at 6.5 m, (provided the image is not limited by diffraction of course). In fact, I admit there is a potential serious flaw in this assertion; I cannot know that all the detail recorded at 6.5m is actually in the image at 13 m. At some spatial scale, the detail in the image will be lost through imperfections and aberrations in the lens, even before the diffraction limit is reached. Thus, it might be true that the TC is really giving a perfect enlargement of the 13 m image (your scenario of performance limited by the lens). I really don't think this is the case though.

This uncertainty is why I added the comparison with the 400mm lens. It demonstrates that a properly designed lens will give much better results than a lens with a TC. You say a "TC is not anything more than a doubler". I say a 200mm lens plus a 2x TC is a nothing more than a (mediocre) 400mm lens. I'm a pragmatist at heart, and what matters is what you get.

cooltouch wrote:
I am a bit surprised, though, that Mark's doubled, interpolated images are as soft as they are. The image doubling I have done don't lose that much detail.


As I said this is because, in my test, the sensor has run out of resolution. The marks in the test chart are imaged to a smaller pitch than the pixel spacing and so cannot be recorded. No amount of scaling or interpolation can recover detail that was never recorded in the first place. This is my basic point - the lens is not the limiting factor when recording distant objects (unless the lens is total crap of course).

A couple of general points about your tests.

Where on the chart did you focus the lens? You cropped out a corner part of the image; if this is not where the lens was focused, the limited depth of field at f2.5 and 33-inch distance may mean this area is not within the depth of field of the lens unless the chart was absolutely dead square to the camera. This may account for the soft results you got at f2.5. Of course, when you used the TC you had a smaller aperture and moved the subject further away, so depth of field would be bigger (and the chart may have been better aligned). (Yes I know the longer focal length with the TC will reduce the depth of field, but overall I think it improves).

When you have an effective aperture of f22 performance will be diffraction limited, hence the softer results (than at f11).

Mark


PostPosted: Thu May 12, 2011 10:30 pm    Post subject: Reply with quote
Hey Mark,

With the two test targets I posted, I focused on the very center of each image. THere was some cropping of the images done because that was what was specified. The first image reads, "For camera, outer edge should just show," referring to the lined borders I'm assuming. But because a smaller view is shown than is actually photographed, it's hard to guess where these edges should be. And for the last image, you'll note the crop proportions in the corners: 1:1, 4:3, 3:2, (and 16:9 that isn't shown). I tried to get things close to 3:2 since that is the image format of my camera, but once again, not being able to see 100% of the viewfinder area makes it a hit or miss affair.

I'd like to respond to your other comments, but it will have to wait. I have other chores that await my attention at the moment.


PostPosted: Wed Sep 30, 2015 3:20 pm    Post subject: Re: Teleconverter Comparison: Tamron 01F vs. Vivitar Macro Reply with quote
cooltouch wrote:
This is in response to the thread running currently that is asking the question, "What is the best quality 2x teleconverter?" I offered to test both a Tamron 01F 2x and a Vivitar 2x Macro TC. The following images are some of the ones I shot for this test. The lens used was a Tamron SP 90mm f/2.5 macro.

The subject is a 50 NT$ bill. This is Taiwanese currency, and NT$ stands for New Taiwan Dollar, most widely spoken of as "NT". Here's a quick shot of the entire note:



This is the full image that the Tamron without teleconverters sees.


I took photos at f/2.5, f/4, f/5.6, f/8, and f/11. Honestly, I couldn't see much difference between the various aperture settings. So for this test, I selected f/2.5, f/5.6, and f/11. If you would like to see images at one of the other aperture values, let me know and I can display them for you.

You will notice some coloration differences between the various selections. I wouldn't put too much emphasis on this. I took the photos using a household incandescent lamp for illumination, then color-corrected them in Canon's DPP software. So, some of the color corrections may be a bit different from each other.

For the test, I focused on the subject's left eye. The images show a 100% crop of the image taken with a Tamron 90mm macro, and images taken with the Tamron and a 01F Tamron 2x TC and a Vivitar macro 2x TC, which were reduced to the same size as the images taken with the Tamron 90mm macro alone. The amount of reduction was approximately 50%.

At f/2.5 indicated


At f/5.6 indicated


At f/11 indicated


I'd be lying if I told you I saw any significant difference between any of these exposures. Well, except maybe at f/2.5, where the Tamron without TCs was a bit soft, but was clearly sharper with either TC. So go figure that one out. Yes, I can notice some very slight differences with some of the exposures. But are they enough to matter, I ask myself. And I just don't think they are.

Stay tuned. For my next comparison, I will do just the reverse. This next one will have the TC images at 100% and I will upsize the images without TCs to the same size. This test will indicate if the TCs provide any additional resolution.

Can this photos be retreved??


PostPosted: Wed Sep 30, 2015 6:59 pm    Post subject: Re: Teleconverter Comparison: Tamron 01F vs. Vivitar Macro Reply with quote
raay04 wrote:
Can this photos be retreved??


Sorry, I don't have the images up at my website. The computer they were on suffered a hard drive crash last year, and I lost a lot of data that I hadn't backed up.

I checked my archives of raw files and it looks like I might have archived them on that same hard drive. So the short answer is "No, I don't have them." But, given time, I can duplicate them -- perhaps even add to their resolution some if I use my 24mp NEX opposed to my 10mp EOS.


PostPosted: Wed Sep 30, 2015 11:09 pm    Post subject: Reply with quote
There's no real world difference between the two TC's. But you would hope that both Tamron and Vivitar would be of decent quality, I wonder how some of the cheaper TC's would perform behind a lens as good as the Tamron ?
Good test, very useful.


PostPosted: Thu Oct 01, 2015 3:20 am    Post subject: Reply with quote
You know, back in my days as a neophyte photographer, when a lens was a lens, I recall fleshing out my Canon AE-1 with 50/1.8 "kit" with a few Albinar products -- the 28mm "macro", 80-200mm f/3.9, and an Albinar 2x TC. The 28mm was a piece of junk, but that old Korean-made 80-200/3.9 was surprisingly good. As for the 2x, I don't recall any specifics, although I know I used it a lot. Probably quite a few of my telephoto slides taken back during the early 80s were taken with that Albinar 2x. So I've gone back and analyzed them, seeing if I can find evidence of image degradation, and the answer is that I couldn't -- although I don't have any photos taken without the TC to compare them to. Still, it makes me wonder . . . I should note also that I put my archive of 35mm slides through at least a couple of culls where I threw out slides that were the least bit out of focus, mis-framed, over or under-exposed, etc. Undoubtedly some taken with the Albinar 2x got tossed. In more recent years I kinda wish I wouldn't have been quite so severe in my culling. Makes me think I could have probably rescued some of them.

But anyway -- it's an easy enough test to determine these days. I've probably got 3 or 4 4-element TCs around here -- leftovers from outfit puchases that I still haven't bothered with putting up on eBay. So I can do a direct comparison between, say, the Vivitar macro TC, against one of these cheapo 2x TCs.

Sounds like an easy enough project. Give me something to do, at least, and might also provide some surprising answers. Who knows?


PostPosted: Thu Oct 01, 2015 12:15 pm    Post subject: Reply with quote
if you can then please dupicate the results, also i have a komura 7 element 2x tc , i will test it on my Tamron 90mm and post results here.


PostPosted: Thu Oct 01, 2015 10:19 pm    Post subject: Reply with quote
I've never owned a Komura TC, but I've heard only good things about them. I'd be willing to wager that yours is as good as the Tamrons and the Vivitar macro 2x.

I see little reason to duplicate the above results, though. If I do anything, it will be different.

Correction: As I was rummaging through my miscellaneous photo stuff, I found that I do indeed own a Komura TC after all. It is a Telemore 95 II, and it also reads 7-K.M.C. Does that "7" stand for 7-element? I'm not sure. Physically, it is only about a millimeter longer than a 4-element Vivitar that I also own, and is at least a centimeter shorter than my Vivitar 7-element macro 2x.

I plan to design a different TC test that will pit my macro Vivitar against my 4-element Vivitar and this Komura. I'll post the results in a new thread, though.


PostPosted: Fri Oct 02, 2015 4:52 am    Post subject: Reply with quote
Michael, The Telemore 95 II is a 7 element converter and the best performer of any of my 2x converters. I also have the Vivitar 2x macro converter but have never compared the two.


PostPosted: Fri Oct 02, 2015 6:10 am    Post subject: Reply with quote
cooltouch wrote:
I've never owned a Komura TC, but I've heard only good things about them. I'd be willing to wager that yours is as good as the Tamrons and the Vivitar macro 2x.

I see little reason to duplicate the above results, though. If I do anything, it will be different.

Correction: As I was rummaging through my miscellaneous photo stuff, I found that I do indeed own a Komura TC after all. It is a Telemore 95 II, and it also reads 7-K.M.C. Does that "7" stand for 7-element? I'm not sure. Physically, it is only about a millimeter longer than a 4-element Vivitar that I also own, and is at least a centimeter shorter than my Vivitar 7-element macro 2x.

I plan to design a different TC test that will pit my macro Vivitar against my 4-element Vivitar and this Komura. I'll post the results in a new thread, though.

Indeed it has 7 elements , i got it cleaned , and opening the optical block revealed 7 elements.


PostPosted: Fri Oct 02, 2015 3:31 pm    Post subject: Reply with quote
Thanks for this info about my Komura TC. Heh, I don't even remember where it came from. Probably part of an outfit I bought and I just set it aside without giving it much thought. I took some preliminary pics with it last night and it sure seems to do a good job. I will do some more work with it and the other two TCs this morning. We have a couple of new white roses that I think I'll use as subjects. Well, perhaps one will do. Stay tuned . . .


PostPosted: Sat Jul 27, 2019 12:04 pm    Post subject: Reply with quote
I think the "without image doubling", i.e., the algorithm used to create the extra pixels, has much more effect on these tests than differences with and without tc. All the without tc images should be compared to downsized images made with tc
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