Tamron 17-50 vc vs non vc (again, sorry :( )

[a1ex2001]

While 9/10 is obviously a stupid figure I would be interested in the true amount.

I'd love to know that figure to but I don't think Tamron will be publishing it anytime soon!

What is interesting is the number of people that have to go through several copies to get a good one. This is what makes me believe the QC is fairly poor. If someone gets a single bad lens then they will report it online, if someone gets a good lens they wont report online, hence it makes an artificially high number of complaints. E.g. maybe only 1% are bad but given the sales figures that may eqate to a fair amount of complaints. However, if someone goes through 2 or 3 copies then this puts a worrying estimate on the number of failures, which must surely be higher than 1%. E.g., if someone goes through 2 to 3 copies then that is a 66-75% failure rate for them personally. These could be unlucky people (1 in 10,000 or 1 in 1 million for a run of 2 or 3 bad copies with a base failure rate of 1%) if many people experience the same then it is not bad luck but simply poor QC.

It is a very very popular lens becuase for what it is it is ridiculously cheap so the numbers will be vast! There is definately an issue but then everyone knows that both Tamron and Sigma have sporadic quality control issues particularly on cheap popular products do a search for soft Sigma 10-20mm and you will discover a world of bile.

I also wonder how many people buy the lens without really checking for calibration or alignment issues and simply accept the performance of the lens? Being a budget lens means lots of inexperienced people will buy it and without knowing better will accept small amounts of softness or focus issues, especially if their technical skills are low anyway. People who lay down the cash for Nikon are probably fairly determined to get a good lens after paying all that money!

I also wonder how many were returned by people determined to find fault with them just so they could return two or three so they get what they percieved as a super special copy. The number of people shooting angled focus charts at close to minimum focus distance at the maximum zoom of the lens and calling it a 'focus test' is huge and almost any lens will exhibit problems under these conditions particularly if it's a cheap lens in the first place.

 

[D.P.]

I also wonder how many were returned by people determined to find fault with them just so they could return two or three so they get what they percieved as a super special copy. The number of people shooting angled focus charts at close to minimum focus distance at the maximum zoom of the lens and calling it a 'focus test' is huge and almost any lens will exhibit problems under these conditions particularly if it's a cheap lens in the first place.

I doubt very many people like going to the hassle of returning perfectly good lenses and dealing with most online stores.

Most people will only shoot some-kind of focus chart AFTER they have poor real world results. And don't mistake shooting test charts - that is exactly what the manufactures do to check focus problems and do calibration. There is no fancy equipment, just a standard angled focus chart.

 

[koolpc]

Primes!! I love them

 

[Alpherah]

Just to update, it arrived on the weekend and its a lot better but still not perfect, i may just have to deal with it though.
Its nice and sharp, even at 2.8 but its front focussing still, its about 7mm out, compared to 3cm out on the first lens.

What's considered to be acceptable anyway? should i send this one back as well?

 

[koolpc]

How can you tell it is 7mm and 3mm out? Do you have a chart?

I really wanted one of these lens but have so been put off now.

 

[Alpherah]

How can you tell it is 7mm and 3mm out? Do you have a chart?

I really wanted one of these lens but have so been put off now.

Yes, using a chart. Although initially i used a setup with some books because the first one was so far off i didn't really need a chart to tell me it needed returning.

 

[olv]

Mine just turned up. Bets on it being a good one?

Can someone recommend a test chart for me please, I've never tested a lens before.

 

[D.P.]

Mine just turned up. Bets on it being a good one?

Can someone recommend a test chart for me please, I've never tested a lens before.

This is a great starting point with all the info you need:
http://regex.info/blog/photo-tech/focus-chart


What you can also try is using Liveview, liveview is not affected by lens calibration issues so if you notice a big difference between phase detection and LV then you know there is a problem.


These charts will check focus calibration, what you should also do is check for uniformity and mis-aligned elements. If you photograph a highly textured wall in parallel you should find the left and right, top and bottom all equally sharp. You may find the edges less sharp than the centre but the important thing is to look for symmetry.

 

[iamtheoneneo]

il tell the story of my lens = nice and sharp has the occasional issues with back focusing but tbh theres zero point in sending it back, for the most part it does what i want it too and if i was that picky on lenses and focusing all my lenses would have to be returned.

 

[olv]

Test shots ahoy. I think I have a reasonable copy. Do you agree? Not very usefully my office laser printer is not very sharp.

17mm f/2.8 - 50% Crop

50mm f/2.8 - 100%

50mm f/2.8 - Crop and resize of above image

17mm f/2.8

17mm f/5.6

50mm f/2.8

50mm f/5.6

50mm f/2.8

50mm f/2.8 - 100% crop of above

I'm not sure what to expect coming from a 24L, but it seems ok?

 

[D.P.]

Seems good to be, focus looks good, enjoy.