[nithin]

I finally got my new Tamron 28-75 and my first shots are a bit disappointing, I couldn't try outdoor due to bad weather, so please bear with some boring comparisons.
I am a new Pentax user and the only other lens I have to compare with is the FA 43mm. I am not sure if its fair to compare a Ltd prime with an 3rd party zoom. My comparisons are at f/2.8 with shutter speed 1/100 & ISO 200. I bought this expecting good sharpness, but wide open at least it isn't. Can anyone comment if I have a bad copy? Or stopping down improves sharpness and IQ? Photos, full & cropped ones are attached.

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[DavidSKAF3]

I have the 28-75 lens too. You're right, there is marked difference. I have not done any such comparisons. But I remain happy with the Tamron lens.

[jrpower10]

Pretty dramatic difference. Try stopping down to see if it improves. I'd also check if the autofocus needs calibration. You can lay a ruler on an inclined surface, put the camera on a tripod, set to center point focus and put the center point on one of the lines. If that line is the best focus then you can eliminate focus problems. If a line in front or behind the one you chose is in better focus, then use the fine adjustment in the camera to get to the focus to the right spot. If you're still unhappy with the result, try returning for a different copy. It'll never be as sharp as the 43, though.

[Docrwm]

That's why I own a 43 and sold my 40. I have an 18-135 because of the WR and versatility but never use any of my 50s any more really because the 43 is just that good.

[Na Horuk]

lol well the FA 43mm is one of the best lenses. I doubt many zooms can come close enough to rival it.
But some more things to keep in mind. Most lenses are not perfectly sharp wide open. Usually they get best sharpness one or two stops down. So the Tamron should be much more usable around f4. The other reasons for fuzzyiness in this photo could be: a) low light, poor light conditions b) handshake blur, mirror slap, pressing the button shake, etc. c) long exposure, slow shutter, d) shallow DoF due to fast aperture e) misfocusing due to low light
It would be much better if you could compare the two lenses using tripod, 2 sec timer, and daylight (or very strong indoor lights). Use the correct WB and lowest ISO. The Tamron still will not beat the FA 43mm, but for a casual viewer (not pixel-peeping) it should be sharp enough.

[Docrwm]

lol well the FA 43mm is one of the best lenses. I doubt many zooms can come close enough to rival it.
But some more things to keep in mind. Most lenses are not perfectly sharp wide open. Usually they get best sharpness one or two stops down. So the Tamron should be much more usable around f4. The other reasons for fuzzyiness in this photo could be: a) low light, poor light conditions b) handshake blur, mirror slap, pressing the button shake, etc. c) long exposure, slow shutter, d) shallow DoF due to fast aperture e) misfocusing due to low light
It would be much better if you could compare the two lenses using tripod, 2 sec timer, and daylight (or very strong indoor lights). Use the correct WB and lowest ISO. The Tamron still will not beat the FA 43mm, but for a casual viewer (not pixel-peeping) it should be sharp enough.

Interesting. He took both photos under the same conditions of the same target. Daylight improves the Tamron that much? Yes a tripod is nice but the 43 was handheld too. No, the 43 IS that much better in my experience.

[Na Horuk]

Interesting. He took both photos under the same conditions of the same target. Daylight improves the Tamron that much? Yes a tripod is nice but the 43 was handheld too. No, the 43 IS that much better in my experience.

You are right, daylight won't improve the lens' performance, but it is generally a good idea to do lens tests in optimal conditions, to see its "best possible" performance. I mean, if they were both handheld, the FA 43mm has the advantage of faster aperture for more accurate focusing, and being smaller for easier handholding. Low light has all sorts of implications, better to remove these variables. But I also agree with you that the FA will beat the Tamrom and that the FA is very sharp lens with nice character. Will be difficult to find lenses to compete with it at all, especially zoom lenses.

[DSims]

You're going to have to stop down the Tamron to about f/3.5 or f/4 to get better IQ. This is true in general for lenses of its class. OTOH the FA43 is just coming into its own at f/2.8, so it will indeed beat the pants off the Tamron at that aperture.

See if you can get pretty good shots from the Tamron stopped down to those apertures. If not, then it's possible your copy isn't so good. Tamron - in particular - has a reputation for having a higher than average % of poorer copies out there. So much so that there have been rumors that they keep the best copies for sale in Japan, and some people have made a point of buying their Tamron lens(es) while there.


Either way, part of what you're seeing is just the cost you pay for the convenience of having a zoom. If you have to stop down the Tamron two full stops, then it's really not that good. But if around one stop gives you images you like, you may still have a very useful tool there.

Although I don't live and die by MTF charts, they can do a fairly good job of guiding you as to where the sweet spots are for a lens. As you can see from these charts, a good copy of the Tamron will yield nice results somewhere between f/2.8 and f/4. Exactly where the better IQ starts is up to you to decide - by taking more test shots with your lens. It could be much improved at f/3.2 - or you may have to go all the way to f/4. Here are the Photozone charts, which make it pretty clear the lens will be weaker at f/2.8: Tamron AF 28-75mm f/2.8 SP XR Di LD Aspherical (IF) (Nikon) - Review / Lab Test Report - Analysis

[beachgardener]

maybe up the shutter speed a tad, change to use flash, test at different apertures, check for front/back focus,

[SpecialK]

The Tamron should not be that bad - it is a highly-regarded lens. Either it is a crappy copy or there are other variable involved.

[nithin]

Thank all for your inputs, I will try again under better conditions ( daylight/ stopped down to f/4) and also check for the front/back focus issue. No one mentioned the possibility of being decentered, but will test for this too.
I find the Tamron front heavy and difficult to handle too. Maybe I'm just spoilt with the fa43.

[tibbitts]

There's no reason you can't do a more controlled test indoors. Hang a test chart on the wall, tripod mount the camera, and manually focus both lenses using live view. Use several apertures so you can compare directly. Without considerable focus adjustment on my k5 (-10), my Tamron 17-50 wouldn't do very well at 2.8 and at that distance.

[bimjo]

Do the test again. Manually focus. Oh, and shoot the 43 wide open too. My copy of the Tammy is worlds better than that. Methinks you need to adjust the AF. The 43 is still gonna be better than the Tammy, but it shouldn't be that much better. If the results are the same you have a bum lens.

[Driline]

Check out the latest review of this lens by xs400. And I quote

"I purchased this lens and planned to use it as a walk around lens. I especially wanted the option to use f2.8 in low light situations. My Tamron 28-75mm was always very soft at f2.8. It was good at f5.6 and above, but that wasn't what I needed. Plus I found the lens to be too heavy and bulky for a walk around lens."

Read more at: Tamron 28-75mm F2.8 AF XR Di LD Macro SP Lens Reviews - Tamron Lenses - Pentax Lens Review Database

I have the FA 43 myself. It's probably the sharpest lens I own plus if used right emits ooodles and ooodles of pixie dust.

[MSL]

I just got a second hand Tamron that in outdoor shots that the previous owner showed me were pretty sharp at 2.8. BUT, and this is a huge BUT, it is a relatively big and heavy lens when compared with a prime. I certainly wouldn't try to one hand the camera for a sharp shot, but I can do this with a 50/1.7 (for example). So even in good light I'd only try a test like this with a tripod. The difference between images #3 and #4 aren't nearly as dramatic as between #1 and #2, so I would discount the first pairing as not being a valid test.

I just did some digging to make my first statement a bit more quantitative and also in line with other comments above. From the lens database:
Pentax 43 - 155 grams, has a sharpness score of 9.8 from 77 reviews
Tamron - 510 grams - sharpness score of 8.7 from 60 reviews.

I'd say more testing is needed under more controlled conditions.