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Help requested: how to compare 2 similar lenses? (maybe 3)
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PostPosted: Fri Oct 24, 2014 7:42 pm    Post subject: Help requested: how to compare 2 similar lenses? (maybe 3) Reply with quote

I have a Vivitar S1 70-210/3.5 (Kiron version) and a Tamron SP 70-210/3.5 (model 19AH) that I would like to compare. (I might or might not be able to add a Soligor C/D 70-210/3.5 lens to the test.)

I've been looking online, unsuccessfully, for ways to compare the lenses to obtain meaningful results without getting too technical (and hopefully without having to work too much setting things up).

Can anybody offer suggestions? What to test, how to test it, etc.

I hope this is not too idiotic a request. Thanks in advance.


PostPosted: Fri Oct 24, 2014 8:42 pm    Post subject: Reply with quote

This is probably the blind leading the blind as I am new to this, but I would take a range of sample images, both indoor and outdoor lighting, as identical as possible given that you'd be doing each set in sequence. I would methodically take said images at different but identical apertures - wide open, closed down and a few points in between. I would also take images that reflect the kinds of subjects I like to take. Ideally one landscape, one portrait, one close up, and one or two others.

I have a set of images I take with every new lens - plants, pets, architectural features at roughly the same sun conditions. It's not perfect but it gives me a general idea to see if a given lens makes the short list. From there, I then try to be more systematic.

I find luisalegria's iconic bird with the 100% crop of the eye to be very instructive!

Hope this helps.


Last edited by JJB on Fri Oct 24, 2014 8:52 pm; edited 1 time in total


PostPosted: Fri Oct 24, 2014 8:46 pm    Post subject: Reply with quote

simplest sharpness, contrast and CA is a newspaper test:

tape a newspaper on a wall, camera on tripod, self timer, fixed time, aperture etc
set zoom & distance so that each lens covers exactly the same area
fixed and good lightning

look at center and corners


PostPosted: Fri Oct 24, 2014 9:58 pm    Post subject: Reply with quote

Those are sound suggestions that can all provide certain points of comparison. A newspaper or similar high contrast subject can give good perspective on resolution, edge contrast and also highlight any tendency to fringing and loss of colour/purpling esp wide open. But won't tell you much about colour contrast, micro contrast, CA or bokeh.
I can't be arsed with exhaustive repetitive images at all f stops and numerous focal lengths. Wide open, one stop down, two stops down to f8 or perhaps f11 is going to cover the desired wide open performance and best performance. Definitely performance at each end of the focal range is of interest, and one or two points in between. Perhaps also performance just in a bit from the ends to see if there is a bit of a falloff eg nearing 210mm. I typically take pics at 135mm to compare with my 135mm primes.
I would suggest RAW, in camera jpg conversion well who knows what goes on, at least using the default settings in eg LR you know things are consistent and when you scrutinise the pics side by side (I find faststone just the job) differences can be attributed to the lenses.

As it happens I have both these lenses too and have also been making a bit of a comparison. Side by side walkaround pics (bit of a pain all that lens swapping but there you are, if you want something approximating a comparison it's better to do that than coming back the next day with the other lens) from experience, are too prone to human operator variation with focus, hand holding etc .... but having said that, I can suggest that cumulatively, over a good number of pics and days of use, a reasonably well founded impression can emerge.
I find that my K-r struggles to discriminate between the resolution of good lenses, the 12Mpx apsc is probably just outgunned... my Lumix G1 offers another perspective in those cases with a higher pixel density. And both these crop factor cameras won't offer much on centre vs edge performances.

This contemporary magazine review is good:
http://www.zen65104.zen.co.uk/boggys_pics/lens%20tests/AmPhotog_Zoom_Lenses_Round_Up_Part-4_19Oct85_300dpi.pdf


PostPosted: Sat Oct 25, 2014 2:40 am    Post subject: Reply with quote

The most meaningful measure for me is my experience with the lens. I'd take each one of for a shoot and see which feels better, then look over the pictures to see which lens provided the most pleasing images.


PostPosted: Sat Oct 25, 2014 3:58 am    Post subject: Reply with quote

woodrim wrote:
The most meaningful measure for me is my experience with the lens. I'd take each one of for a shoot and see which feels better, then look over the pictures to see which lens provided the most pleasing images.

+100


PostPosted: Sat Oct 25, 2014 5:35 am    Post subject: Reply with quote

That's the most fun method, but not very objective. I noticed that I often get better results with technically not the best lenses. Too much goes into picture taking: light, luck, inspiration. Lens qualities is only maybe 10-20% of the end result.


PostPosted: Sat Oct 25, 2014 8:24 am    Post subject: Reply with quote

depends how much time you have and work you want to do

newspaper test for 3 lenses takes about an hour including setting up and reviewing the results

if you choose a newspaper with different color pictures you can sort of see the saturation etc too

if you want a hobby or profession as a lens critique, just go around in different circumstances and subjects with slightly different lenses. that task will never end (or reach some conclusion). see how many pages this forum subsection has. Very Happy


PostPosted: Sat Oct 25, 2014 8:36 am    Post subject: Reply with quote

Agreed.

Sharpness is overrated, what about how it handles? What's the zoom mech like? does the aperture move in 1/2 stops? What's flare like? how heavy is it?

take em out one at time and use 'em you will quickly get an idea for which you prefer.

With seemingly so much variation in quality as a result of age, Well, just shoot with them, forget the test charts.


PostPosted: Sat Oct 25, 2014 2:58 pm    Post subject: Reply with quote

I have lenses that I have used to make sharpness comparisons with and then struggle to see much of a difference. I might take those lenses out on a shoot and immediately feel a difference when using them. In one case that I remember well, I was using a favored 105mm lens when I switched to another and it immediately struck me how the viewing through the lens and the handling was much more enjoyable. That is the handling part, but then there is the results part. I have lenses that always seem to give me what I call the smile factor when viewing the images. It is sometimes hard to define why, but I find justifying it far less important than my actual experience. One such lens is my Lydith; it might not win any side by side comparisons with another very good lens, but the images from it tell me it doesn't matter. Of course there are some lenses that are so sharp that it is an obvious attribute, but even with those I don't always choose them. An example of that would be the Vivitar Series 1 2.3/135 and the Tair-11. The S1 is a razor and the Tair has wonderful bokeh. They are my top at that focal length, but I use them both equally- maybe the Tair a little more.

Everyone knows how sharp the Flektogon 2.4/35 is and how close it focuses, but I will choose the Topcor 2.8/35 over it 96% of the time. Long story short is that a test shot might tell you something, but it's a small part of the story and not the most important for real photography. Like most people, I started with making those comparisons, but then learned how little they mattered. Then I learned that the lens itself is only a very small factor in the overall performance of a photographer.


PostPosted: Sat Oct 25, 2014 3:05 pm    Post subject: Reply with quote

I don't do a direct comparison on my lenses. I do try my best to discover their strengths and understand the limitations...


PostPosted: Sat Oct 25, 2014 3:10 pm    Post subject: Reply with quote

calvin83 wrote:
I don't do a direct comparison on my lenses. I do try my best to discover their strengths and understand the limitations...


Yes, and then play to each.


PostPosted: Sat Oct 25, 2014 3:45 pm    Post subject: Reply with quote

Different people will have different criteria. Some people will think flare is a bad thing while other not. Some lens have very low contrast but I have seen many nice photos under certain condition. If you want to a comparison for yourself, focus on what you care most. It can be handling, color, resolution, aberrations or any other quality.

Make sure the test is perform with same camera setting and under similar light condition. Here is a good test on our forum http://forum.mflenses.com/twelve-2-8-135mm-lenses-compared-on-5dmkii-t39463.html .


PostPosted: Sat Oct 25, 2014 5:26 pm    Post subject: Reply with quote

i would be interested in some sort of test as i had the tammy but did not keep it as it was not as sharp as i expected..it probably very very good for a zoom from its day and probably over hyped that why i was a little disappointed and i probably unfairly compared it to my EF 17-55 F2.8 IS and L zooms i have..its final nail in its coffin was me struggling to focus it on my 20D..but now i have a nex i have been thinking about it again
My research at the time suggested the tammy was sharper than the Vivita.. in a lens i look for sharpness and bokeh (often hard to get both at the same time) and the color


PostPosted: Sat Oct 25, 2014 5:36 pm    Post subject: Reply with quote

I'm in the same boat as just using the [each] lens for a day or so & seeing how I 'like' them. There is more than just sharpness but saying that, sharpness [or accurate focus Wink ] is pretty important to me at least. There are other factors such as how the lens looks/feels, focus ring, stops etc as has been mentioned.

Saying that, I wouldn't mind flat newspaper testing mine simply for my own benefit as I find the manual focus lenses soft anywhere but dead centre. Again, if you know these things you can work around them when shooting.


PostPosted: Sat Oct 25, 2014 5:43 pm    Post subject: Reply with quote

Thanks everybody for the feedback. I'm fully aware that the best way to know which lens is the best for you is to go out and shoot with it. The choice is always subjective. For example, I prefer two-touch zooms over one-touch, which is why I'm looking into finding a Soligor 70-210/3.5 to potentially replace the Vivitar and the Tamron – even if it ends up being slightly inferior optically.

Head-to-head comparisons, however, can provide useful objective information to others. Assuming they're done right, that is... which is why I started this thread Wink


PostPosted: Sat Oct 25, 2014 6:09 pm    Post subject: Reply with quote

I have found this thread very instructive so I thank you for starting it. I particularly appreciated Woodrim's comments. Additionally, as I've been testing, there is sometimes an ineffable sense of excitement when you pull up the images which may not necessarily correspond to technical specifications. Sometimes there is that "aha" moment when what you see is what you hoped to capture. I may not be explaining this that well, but I felt it when I first used both the Helios 44-4 and the Mamiya Sekor 50/2 chrome nose. Both come favorably reviewed but are also very common lenses and neither is pricey. It was kind of a gut thing rather than a prestige thing.


PostPosted: Sun Oct 26, 2014 2:49 pm    Post subject: Reply with quote

Or you can shoot bricks (a brickwall) from a tripod, look for one close to home, then go from open aperture to F8, at the exact same distance, viewing angle, shutterspeed & iso with your camera setup...then you could compare..the distortion, sharpness, vignetting...for example.


PostPosted: Sun Oct 26, 2014 3:55 pm    Post subject: Reply with quote

The usual brick wall shots are straight on and subject to focus variation, as are most tests. I do use a brick wall on occasion just for appreciation of sharpness, but take the pictures on an angle which guarantees some point will be in prefect focus. The bricks have tecture that will help with the evaluation.


PostPosted: Sun Oct 26, 2014 7:02 pm    Post subject: Reply with quote

Fantastic image, Woodrim!


PostPosted: Thu Oct 30, 2014 7:13 pm    Post subject: Re: Help requested: how to compare 2 similar lenses? (maybe Reply with quote

invisible wrote:
I've been looking online, unsuccessfully, for ways to compare the lenses to obtain meaningful results without getting too technical (and hopefully without having to work too much setting things up).

Can anybody offer suggestions? What to test, how to test it, etc.

There are many ways to test a lens. However, if it is not clear what to expect from a lens, any test will be meaningless. Indeed, "if you don't know where you're going, any road will get you nowhere." - Henry Kissinger

A lens is an optical device whose function is to project an optical image of the physical world onto a digital sensor (or a piece of photographic film). We know how an ideal lens would behave; therefore testing a real lens is basically comparing its image with that produced by an ideal lens.

The first optical instruments were perhaps the telescopes used by astronomers to watch stars and planets. They soon discovered that the stars did not appear as points of light, but as small blurs. These blurs prevent, for example, that two nearby stars are seen separately. Therefore, it is important that a telescope be tested for separating power, or resolution. When a telescope is pointed to an object with a spatial extent, like the moon, the limited resolution makes the details difficult to see. In this case we say that the image lacks sharpness. A photographic lens is normally used to photograph objects with spatial dimension, so sharpness is one of the most important attributes of a good photographic lens. The biggest challenge of the optical designers is how to design a lens with excellent sharpness and moderate price. That said, there are other characteristics of a lens which are also important, depending on the application: distortion, light fall-off, chromatic response, resistance to flare and ghosting, etc.

Some people believe that the best way to "test" a lens is simply to start using it. Well, I don't think this procedure is the best. To understand my point of view, imagine a soldier that receives a weapon which he is not familiar with, and immediately goes to a battle. He will have the opportunity to "test" his weapon in the battle, but is this reasonable? The smartest/safest thing to do would be to test the weapon BEFORE, not DURING the battle, right? Likewise, a photographer should exhaustively test his/her lenses BEFORE, not DURING a serious photographic work.

A recent experience: Last week, my sister-in-law bought a Nikon D5300 with an 18-140mm kit lens, and let the camera with me to test it. I took the opportunity to compare the performance of that lens with primes from 30-40 years ago.

The focal lengths marked on the barrel are:18, 24, 35, 50, 75 and 140mm, so one should take at least 3000 pictures to know the lens well by the "rule of 500". Of course, it would take me several months to test the lens. Instead, I used a more scientific approach and spent less than two hours to collect and analyze all the data I needed. Among a lot of other interesting things, I found out that the performance of those modern kit lenses is excellent, and they often outperform old fixed focal length lenses.


PostPosted: Thu Oct 30, 2014 7:28 pm    Post subject: Re: Help requested: how to compare 2 similar lenses? (maybe Reply with quote

[quote="Gerald"]
invisible wrote:
...I found out that the performance of those modern kit lenses is excellent, and they often outperform old fixed focal length lenses.


Wow, that seemed an abrupt end to your post. By what measures have you come to that conclusion? It has not been my experience with kit lenses and one might wonder why then that we all are so enthusiastic about the old primes.


PostPosted: Fri Oct 31, 2014 1:51 pm    Post subject: Re: Help requested: how to compare 2 similar lenses? (maybe Reply with quote

[quote="woodrim"]
Gerald wrote:
invisible wrote:
...I found out that the performance of those modern kit lenses is excellent, and they often outperform old fixed focal length lenses.


Wow, that seemed an abrupt end to your post. By what measures have you come to that conclusion? It has not been my experience with kit lenses and one might wonder why then that we all are so enthusiastic about the old primes.

I did not want to make my too long post. Besides, the topic was not about kit lenses, but as kit lenses is very popular, I'll like to add some comments.

My experience with kit lenses is quite limited: I had the opportunity to quickly try a Canon 18-135mm sometime ago, and now the Nikon 18-140mm. The Nikkor is the newest design and seems to be the best lens in the category. Sony also has an 18-135mm lens, but according to testing done by Kurt Munger, the performance, especially at the edges and corners, is much lower than the Nikkor.

My conclusion after testing the Nikkor 18-140mm was that this lens gives the old primes a run for their money. Of course, the old primes have the advantage of a larger aperture, typically F2.8, or even F1.8 or faster in the case of a normal lens. In contrast, the maximum aperture of a kit lens is F3.5 at the wide-angle end and F5.6 at the telephoto end.

To give an idea of how the performance of the Nikkor 18-140mm is surprisingly good, I will show some comparisons with two old prime lenses known to have above average performance. One is the 6-element SMC Takumar 135mm F2.5, and another is the CZJ Sonnar 200mm F2.8.

I measured the MTF50 values across the field, but to simplify the comparison I will show just the performance in the corners, which is the region where zoom lenses usually have poorer performance. I will present only the crops of the test images at the upper left corner, and not the MTF50 values, so each person can judge the performance with his/her own eyes. I suggest paying attention to the contrast of the dark lines and the acutance of the edges of the squares, which are directly related to sharpness of the lens.

The crops are all 100%, which makes the comparison fair because the Nikon D5300 used with the kit lens and the Sony A99 used with the prime lenses, are both 24MP cameras.

A) Nikkor 18-140mm versus SMC Takumar 135mm
The comparison was made with the Nikkor set at 70mm, which corresponds to an equivalent focal distance of 105mm, which is close enough to 135mm of the SMC Takumar focal length. Of course, in both cases the test chart was framed to fully fill the field.

Wide open:


F8:



B) Nikkor 18-140mm versus CZJ Sonnar 200mm
The comparison was made with the Nikkor set at 140mm, which corresponds to an equivalent focal distance of 210mm, which is close to 200mm of the CZJ Sonnar focal length.

Wide open:



F8:



Conclusions
1) The prime lenses have the advantage of a larger aperture, but the performance wide open is not always spectacular.
2) The Nikkor 18-140mm has very good performance wide open, and no significant improvement occurs when the aperture is closed to F8, for example
3) At aperture F8, the prime lenses can have excellent performance, but the Nikkor is not far behind.
4) It was not shown, but the same pattern of behavior repeats for other focal lengths.


PostPosted: Fri Oct 31, 2014 2:09 pm    Post subject: Reply with quote

You're right, we shouldn't hijack this thread, but since we already have, I'll provide some comments. I don't find it useful to compare two lenses at wide open when the aperture is that different. Stopping the Tak down to f/5 would have been a more equal comparison. Using different cameras introduces other factors. For one, the pixel density is different and if the primes were used on an APS-C camera, they would have different (better performance at the edges. In any case, I think from what you've shown, the primes will outperform the kit when all things are equal.


PostPosted: Fri Oct 31, 2014 4:39 pm    Post subject: Reply with quote

woodrim wrote:
Stopping the Tak down to f/5 would have been a more equal comparison.


I didn't test the Takumar for F5 but I have results for F5.6.
I added the test pictures taken with the Pentacon 135mm F2.8 and the CZJ Biometar 120mm F2.8, both lenses working at F5.6.
Note that only the CZJ Biometar outperforms the Nikkor at F5.6 but the difference is small.