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PostPosted: Fri Nov 07, 2008 8:42 pm 
So I picked it up yesterday in the store I'm working in and had the chance to quickly get a first impression of it today.

Keep in mind, that this is a superzoom which will inevitablely have to make compromises. I don't want to start a discussion on the subject if such a lens is "good" or "bad" - it has its clear purpose of serving as an allround lens for travelling when you just don't have the time to switch between several lenses all the time. It's also very light for those occasions where you dont want to pack yourself with multiple heavy lenses. If you need the best possible quality for a very special scene, you still will have to take a prime (or maybe a small-zoom-range) lens.

Build Quality
Basicly, when you pick up the lens, you feel that you've got a solid piece of glass in your hands. The AF, VC and Zoomlock switches are all reasonably placed so they can be reached well. The zoom has got some resistance to it to reduce lens creep (more on that in a moment). Between 70 and 120mm the resistance reaches its summit. However after a day of using it already starts to run a little smoother.
The front element is not rotating, which certainly is great news if you want to use a filter. Due to the wide angle, the included lens hood is naturally quite small, yet well shaped (bigger on the top and the bottom) to maximize its potential. The manual focus ring is a bit loose, but reasonably sized.

After so much praising you probably already suspect that there are some downsides as well, so here we go... The inner tube wobbles a little bit but it's not critical. Probably the biggest issue is lens creep - If you point the camera towards the ground and shake it, the lens will zoom in due to the weight of the inner tube(s). While I don't know exactly how big of an issue this is with other superzooms, I think it's still within reason on this one. As mentioned before, the zoom ring is pretty loose when switching to MF, so manual focusing is not that great.

Overall, Tamron has done a pretty good job with this lens, apart from the usual superzoom issues, such as lens creep.

Autofocus
I've read in various other comments about this lens (especially from those with Nikon mount) that the autofocus was very slow so I was quite worried when I did my first testshots. I discovered that in daylight, the autofocus is actually nothing to worry about - surely, it aint as fast as a USM Autofocus from Canon and if you want to professionally shoot sports, you should look for another lens - BUT for normal use it certainly is quick enough. In low light though, the story is a slightly diffrent one: The focus gets quite slow, taking about 1-2 secs if the subject is close and ocasionally it starts to hunt. At times it's actually unable to focus at all until you try a second or even third time.

Conclusion: The AF is just fine in good lighting conditions, whereas in low light it can get quite slow.

Vibration Compensation
Not much to write about here... it works very fine - I was able to shoot at 1/60s at 270mm without problems and down to 1/8s at wider angles. I guess someone with more steady hands will even be able to take 1/4s shots without a tripod. You can tell when the stabilizer starts to work by its relatevely loud noise, it starts working when you half-press the shutter release button, and stops about 2 seconds after you stop pressing it again.

So the Vibration Compensation is probably the biggest improvement over the previous 18-250.

Optical Quiality
For optical Quality, check my thread in the lens galery. To write a quick conclusion here (personal impression after 1 day of use): This lens is tack sharp in the center, still very sharp towards the edges, but starts to smooth out a little in the corners. CA's are nothing to worry about as far as I can tell at the moment, and vignetting is well controled.

Conclusion
The Tamron 18-270mm certainly is a compromise - but a good one! Optical quality is surprisingly good (at least as far as I can tell until now), and I'm especially pleased by the low amount of CA's. Build quality is ok, but not great - certainly good enough for a holiday. Vibration Compensation works great, which makes up a bit for the rather small max aperture. There are 3 bad points, 2 of which can be overlooked for an allround lens in my opinion: Probably the biggest issue is the slow and sometimes hunting AF in low light. typical for such a lens, it tends to creep when pointing up or down and lastly the aperture at 200< is quite small (f/6.3).

So overall I think I can highly recommend the Tamron 18-270 to anyone who's looking for a travel lens.


Last edited by Nostrum on Sun Nov 09, 2008 10:30 am, edited 6 times in total.

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PostPosted: Fri Nov 07, 2008 9:34 pm 
Very nice. How does it compare to the old 18-250? I notice that in the UK, the 18-270 is almost double the price of the old 18-250 and I'm wondering if there's a good reason to pay that premium for an extra 20mm?


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PostPosted: Fri Nov 07, 2008 10:07 pm 
In switzerland, the price of the 250 one is about 2/3 of the 270's.

The BIG diffrence between the 2 is the Vibration Compensation, which is lacking in the previous version. Of course, for you as a sony user, you don't care about that - but for canon and nikon that's a great improvement. Anyone who ever tried to shoot at f/5.6 or higher at >200mm without Image Stabilization knows what I'm talking about :)


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PostPosted: Fri Nov 07, 2008 10:49 pm 
That makes sense! I completely forgot about in lens stabilization as that's not a feature I'm concerned with ;). Guess that explains the huge jump in price for "only" 20mm. This also probably explains why the 18-250mm is almost impossible to find in Sony mounts while it's widely available in Nikon and Canon mounts.


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PostPosted: Sat Nov 08, 2008 6:35 am 
It might also explain, why Tamron is not (or at least not yet) releasing a Sony mount version of the 18-270 ;)


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PostPosted: Sat Nov 08, 2008 8:30 pm 
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Hi Nostrum, thanks for the report...

Are you noticing any coloured fringing or softening at certain focal lengths, particularly when zoomed-in?


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PostPosted: Sun Nov 09, 2008 10:15 am 
I first thought the lens was a bit soft at 18mm, but I've just done some shots on a tripod, manually focused of a test sheet and the center sharpness was actually no issue, not at 18mm either. Towards the edges it gets a little soft at aperture wide open. stopping down 1 or 2 stops helps a lot though

Even with the test shots, i still fail to detect any significant weak spot in the zoom range. In the "middle" range of 40-120mm or so, I would even dare to say that the lens is sharp in the corners as well, especially if stopped down a stop from max aperture..

All zoomed in with aperture wide open it seems to get a bit dreamy, again stopping down a stop helps a lot (however that will be difficult in practise since the max aperture is allready as small as f/6.3 and you need quite a fast shutter speed at 270mm..)

One thing which in my opinion is nothing short of AMAZING is the low amount of Chromatic Aberrations! I was actually UNABLE to find any of them until I set up a special scene to find some (some branches in front of the bright sky), and even then they were invisible unless you zoom in to 100% and start searching for them.

I'm really no expert, so don't take any of that for granted ;) I'm very curious what results the professional tests are going to provide!

Anyway.. my final conclusion up to now is this: The Tamron 18-270mm certainly is a compromise - but a good one! Optical quality is surprisingly good (at least as far as I can tell until now), and I'm especially pleased by the low amount of CA's. Build quality is ok, but not great - certainly good enough for a holiday. There are 3 bad points, which can be looked over for an allround lens in my opinion: Probably the biggest issue is the slow and sometimes hunting AF in low light, typical for such a lens, it tends to creep when pointing up or down and lastly the aperture at 200< is quite small (f/6.3).

So if you're looking for a travel lens, the Tamron 18-270mm is certainly a great pick.


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PostPosted: Sun Nov 09, 2008 8:09 pm 
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Hi Nostrum, thanks for that!

How do you find your Canon's AF with the lens when it's zoomed-in? As you may know, the AF sensor is happiest working at f5.6 or brighter, so lenses that are slower than this - such as yours when zoomed-in - may cause some problems. That said, the Sigma 'Bigma' 50-500mm seems fine in that regard at 500mm.


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PostPosted: Mon Nov 10, 2008 2:28 pm 
In low light zoomed in all the way it does actually fail to focus pretty often - especially if the object is rather close. In daylight i'm not experiencing anything like that.


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PostPosted: Mon Nov 10, 2008 6:56 pm 
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I should be able to give a second opinion on Wednesday, as I just ordered one...

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Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.


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PostPosted: Wed Nov 12, 2008 8:07 pm 
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Mine arrived today. Not done much with it yet, although I have a curious effect I can't explain at the moment. In two sets of shots, I'm getting brightness variations. One set taken indoors there is a variation in different areas. On another set of 5 taken outdoors, the 1st and last are darker than the mid 3. This was over 8 seconds and exif shows the same settings were used (aperture, shutter, ISO). Other shots taken outdoors did not show this effect.

Elsewhere: AF speed/noise is typical for this type of lens and I've not had any trouble getting lock. The VC does what it should. Maybe my sample is tighter, but it does not creep from either extreme when angled up/down. As a minor annoyance, the focus ring turns even in AF.

Edit: Forgot to say, in one test CA was pretty bad on the borders while nothing visible in center. This was at 270mm wide open with a very high contrast area (white sky vs dark building). Done a little testing at home for the level variation. My current best guess is there might be two things going on, neither of which particularly specific to this lens but for some reason I only noticed now. I suspect artificial light flicker is the cause of the indoor one. Not sure on outdoor one yet but have to put ghosting on top of the suspect list.

_________________
Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.


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PostPosted: Wed Nov 12, 2008 8:55 pm 
well i might have described the lens creep a little worse than it actually is. Also, it starts to get a little worse (though the zooming gets smoother at the same time ;) ) after using the lense a bit.

I had some similar experiences with some pictures just getting too dark with no obvious reason, it is however not reproducable


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PostPosted: Wed Nov 12, 2008 9:14 pm 
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Did you experience the brightness variation with this lens or in general? For me the 50D is still very new so I don't know yet if it might do things a little differently from the other cameras I have when used indoors.

Now I should go and take more test pictures :D

_________________
Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.


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PostPosted: Wed Nov 12, 2008 9:28 pm 
only with this lens.. but it might have been bad metering caused by bright sky or something.


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PostPosted: Fri Nov 14, 2008 3:06 pm 
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I just took it down the park. Unfortunately it was dull and overcast at the time, so I was shooting mostly wide open. Typically the sun has just come out now that I'm home and downloaded the images.

My general impressions are that regardless of focal length it is a bit soft although it wouldn't be helped by needing higher ISOs. Stopping down a bit helps a little but diffraction softening doesn't seem far away either. Tamron haven't performed any miracles in optical quality here. You wouldn't say this is a sharp lens, but it is within expectations for this class of lens. It seems comparable to or slightly better than the 1999 vintage Tamron 28-300 I have on Sony, but that has a smaller overall range and no VC.

I haven't looked too deep into CA, but it's certainly there at moderate levels. Seen at 18mm and 270mm but not taken much in between. Generally fine in the middle, becoming noticeable toward the edge centers and getting worse in corners.

So as a summary I'd say for now it meets reasonable expectations from a lens of this zoom range. I'll put up samples later.

To finish off, I had an oddity again. There was a magpie in the car park so I got the camera out right away. While the AF was working, suddenly the viewfinder went much darker. I was not holding the DoF preview button. It stayed like this until I pressed the DoF button. Has been normal since. I have no idea if this is camera or lens related, or both even. From what I have seen so far, I haven't noticed any other outdoor brightness variation.

_________________
Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.


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