[reh321]

and I don't think all of them are current.

More important for this discussion, several are a cheaper / more expensive pair; for example. Pentax does not need three sets of additional 18-55 f/3.5-5.6 lenses, especially since they have 18-50mm and 18-135 in in-lens AF motor lenses already.

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Last edited by reh321; 01-28-2020 at 11:37 AM.

[Serkevan]

I consider a rebrand to be lenses made by tamron for pentax brand, even if pentax puts the propriety lens coating on then ships it back.
A licensed product would be Pentax/Ricoh purchasing the optical formula and manufacturing it from scratch themselves.
For cost convenience they may also be sourcing parts from tamron or their suppliers.

The key difference is where the profits flow to and who has control of the manufacturing process and timeline.

Heh, then half the lenses from Canikony or Pentax are rebrands, because Tamron manufactures a lot of OEM lenses (mostly kit lenses IIRC).

[house]

Some people are said to be like St Peter, they only believe what they can see with their own eyes.

My take on that D-FA 70-210 lens, after having browsed throught a hundred of lens test charts, of M43 lenses, APSC lenses, FF lenses and MF lenses, I bet is going to be sharp in the center @ about 45lpmm and about 30lpmm in the outer region.

When looking at hundred of charts, I realized a few things:
- the really cheap lenses tend to have poor corners, compare to mid-range and high-end lenses
- a lot of primes lenses are no better in corners than good zooms, it's just that primes are smaller and faster. The prime is make for making bokeh, more than it is made for shooting between f8 and f16, so I guess that's why prime lens designers don't care about corner sharpness on primes.
- some of the expensive lenses are no better than average priced lenses (double price lenses aren't twice as good as half price lenses, often the double price lens is only a little better)
- some high brand lenses (Zeiss, etc) may be sharper , but not as much sharper as the price premium might indicate at first sight (basically you pay some money for the Zeiss label on the lens barel)


Last but not least, MTF charts all look about the same regardless of the format, I wondered why it is so, if the FF lens is tack sharp on a crop, why the apsc lens isn't ? I can up with an answer for myself that is: all lenses are cost-size-weight tradeoff so that they are acceptable sharp and based on competing next format.

No worry, no miracles expected either, almost every lens is sharp in the center and drop to about half sharpness in corned. On full frame, even 25lpmm is good enough to deliver 8Mpixels equivalent in corners, no one see the difference between two lenses on a large 4K monitor view at diagonal of display distance.

Did you take focal length into account when comparing those hundreds of charts? To me it sounds, based on your observations, that you didn't? You don't buy a uwa prime for bokeh. Lens rentals have confirmed that zooms may be good in the center but never match primes at the corners and suffer more from sample variation.

[repaap]

Don’t really see what is the problem at here. First of all, tamron is not anymore what it used to be. Second, everyone is doing this, and not just at photograpy world. It is efficient. And as for example Sony who has done lot of sensors for everyone and also use Tamron and Zeiss(who does not) to make their lens line up Quickly and efficiently. We also have K28/2 and FA 43 which are shared my other manufacturers, why this would be any different and ’not appropriate’? Especially nowadays when resourses are getting few’er co’operation should be more and more.at any field.

Just saying. Chill guys..

[house]

Third party brands like Tamron and Tokina have a lot of experience making lenses. Most likely they have more experienced staff than Pentax at all levels considering their relative output. The reason they (used to) make so so lenses is because they were made to meet a price point. It's not a lack of skill or talent or any inherent godliness that resides in the name brands and not the third party. As you know they make pricey lenses for other brands and hence have proven they can do high quality. Their own products are also beating name brands as seen with the new tamron 35mm.

[biz-engineer]

Did you take focal length into account when comparing those hundreds of charts?

Yes, I also considered the focal length. From standard to tele lenses, some lenses can have corner nearly as sharp as center. But among wide angles lenses I have found any that manage to have sharp corner, at best corners are acceptable, worst wide angle lenses including primes have corners completely blurred. Zooms can't achieve the peak center sharpness as much as primes can, but that's not necessarily true in corners, some zooms outperform primes in corners. Anyway, long story short, chasing corner sharpness in one format is not as effective as moving up to the next format. Given the circular geometry of lenses, light propagation in straight lines, and rectangular camera sensor, it should be a surprise that lenses will never deliver homogeneous performance accross camera sensors, unless at the cost of huge efforts.

[normhead]

Did you take focal length into account when comparing those hundreds of charts? To me it sounds, based on your observations, that you didn't? You don't buy a uwa prime for bokeh. Lens rentals have confirmed that zooms may be good in the center but never match primes at the corners and suffer more from sample variation.

You have the link?.. I'd go along with zooms don't match primes at every focal length. But a lot of zooms do at one particular focal length or range, and everything else is gravy.
I've compared my DA*60-250 to a 90mm and Tamron 90, a highly respected lens on all formats. The images were indistinguishable unless, you really squinted, there were slight difference in micro-contrast.. So straight up, I've tested your theory, and it came up wanting in the real world. I'm quite happy to accept that on a test chart you might be fooled by insignificant differences. One number is better than the others, it has to be better right. In fact my biggest quarrel with test charts would be, until it's established what a significant difference is for an average viewer, they are pretty much meaningless. My guess is it the point is somewhere above 100 lw/ph and less than 200 lw/ph, but, I've never seen it confirmed in any way.

And another thing I've noticed, test chart sharpness does not always translate into the best rendering. You can say one lens is test chart sharper, that doesn't automatically translate into better images. The size of the print and viewing media matters.

There are situations where I will happily shoot with my FA 35-80 I paid $79 for. If the size is going to be reduced and you're viewing on a TV monitor it renders beautifully. And in a 7 lens forum comparison almost 30% voted for it as their favourite 35mm, ahead of the DA 35 2.4 and many others that technically are rated much sharper, almost 30% of the forum voted for it, 50% more than you would expect from random selection. That is well above standard deviation. For reduced sized rendering it was the best of the 7 lenses tested.

Basically, the more experience you have, the more you rely on your experience with a particular lens, understanding what each lens has for it's strength and the less you rely on test charts. Another example would be the 21 ltd. Not a test chart favourite, terrible in high contrast situations, but if you know where to use it, low key mellow pastel type images, it produces stunning results. You can't tell that from a test chart.

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Last edited by normhead; 01-28-2020 at 03:47 PM.

[biz-engineer]

In fact my biggest quarrel with test charts would be, until it's established what a significant difference is for an average viewer, they are pretty much meaningless.

The library nearby receives two photo magazines, they have all issues from the last 3 years. One magazine publish their own lens tests on bench, for each lens their show the MTF chart and the actual crop of the test chart image center, mid-frame and corners. You can see how the same test chart image looks like and compare lens to lens by bringing the pages of magazin next to each other. I compared the corner test chart image between Otus prime and some Tamron lens (or whatever Zeiss or something else, that's not the point), the Tamron is almost as good, but the Otus price is a shame. I think when there is 10% better corner and it's a Zeiss instead of a Tamron, the reviewer will say in their youtube video "Ohhhhh that Otus lens is soooooo much better", while in reality it's only a little better and 3 times the price. How much better is a lens compared to average is totally inflated by marketing talk. I think, unfortunately, all lens designers face the same constrains of optics, regardless of the name of the company their are working for...

[normhead]

The library nearby receives two photo magazines, they have all issues from the last 3 years. One magazine publish their own lens tests on bench, for each lens their show the MTF chart and the actual crop of the test chart image center, mid-frame and corners. You can see how the same test chart image looks like and compare lens to lens by bringing the pages of magazin next to each other. I compared the corner test chart image between Otus prime and some Tamron lens (or whatever Zeiss or something else, that's not the point), the Tamron is almost as good, but the Otus price is a shame. I think when there is 10% better corner and it's a Zeiss instead of a Tamron, the reviewer will say in their youtube video "Ohhhhh that Otus lens is soooooo much better", while in reality it's only a little better and 3 times the price. How much better is a lens compared to average is totally inflated by marketing talk. I think, unfortunately, all lens designers face the same constrains of optics, regardless of the name of the company their are working for...

As tolerances get tighter, manufacturing costs go up. Not much you can do about it. And only of relevance to those who are not oversampling. Once reduced to 3850 x 2160 for my HD TV there's no real advantage.

The first question folks should ask selecting lenses is "do I ever see my images at full size?"
The answer is always "oh ya, every image I take has to be perfect unreduced."
You can waste a lot of money that way.

[house]

You have the link?

Lens Rentals | Blog

That's just one article but it's been mentioned numerous times. It coroborates your view that some fl might be good for one specific lens.

[reh321]

As tolerances get tighter, manufacturing costs go up. Not much you can do about it. And only of relevance to those who are not oversampling. Once reduced to 3850 x 2160 for my HD TV there's no real advantage.

The first question folks should ask selecting lenses is "do I ever see my images at full size?"
The answer is always "oh ya, every image I take has to be perfect unreduced."
You can waste a lot of money that way.

Back when I was a Canon user, probably around 2013, a writer found distortions in a Sigma 18-270mm lens; he zoomed in to a house in the right side of his image to show it. I only used the lens for a year, but I never did see a clear result of that distortion. Some people should take more photos and spend less time looking for problems.

[wed7]

Yay. Now Pentax can line up the 85, 35 and 24

[reh321]

Yay. Now Pentax can line up the 85, 35 and 24

Hopefully, the 35mm and the 24mm will be slightly "imperfect" affordable DFA lenses.

[biz-engineer]

Once reduced to 3850 x 2160 for my HD TV there's no real advantage.

You touch an important point, camera lens makers know that, that's why all lenses drop from 50lpmm down to 25lppmm. 25lpmm is just fine on 4K. Optically it is possible to achieve significantly more than 50lpmm, some industrial lenses can achieve as much 400lpmm, but it's too costly to put that into a camera to take pictures of flowers and that kind of things. So to me it seems that the baseline target for photographic camera lens is 50lppmm in the center and 25lppmm in corners , for any digital format. IMO, there is way to much importance given to brand names, all lenses from all camera makers and third party lens markers are all about good enough for the task of taking pictures.

[normhead]

Lens Rentals | Blog

That's just one article but it's been mentioned numerous times. It coroborates your view that some fl might be good for one specific lens.

Thanks, those guys never post a bad read.