[Dan Rentea]

Earlier @normhead stated it is 135mm for close focus, I have no idea if this is true though.

He may be true also. There are a number of factors that can give different results, including copy variations of the lenses.

At f4 this may or may not enough for subject isolation, but it is not actually great.

These are 2 examples, the one from the top being the image of my friend, taken with 85mm f1.2L lens on a full frame, at f2. On the bottom it's my image taken at 150mm, f4 (with 70-200mm f4 lens on a full frame). He was shooting from the ground level and he used a gold reflector to bounce the light. I was shooting from the eye level from behind my friend and a little on his left. I used a white reflector because I liked her tan. If I wanted to get similar shot as my friend, I would have used the gold reflector, back up a little to use 180mm instead of 150mm and I would have lowered also my camera. But subject isolation wasn't a problem for me with a 70-200mm f4 lens even shooting next to a guy with an 85mm f1.2 lens.

I personally do not shoot portrait with lenses longer than 105mm, because even at 105 it is already very flat in perspective, but rhis is another story.

I shoot portraits with any lens, depending on the available space I have on location. I wouldn't call the below images being flat in terms of perspective due to the fact that were taken with focal lengths longer than 105mm, but I think it's a matter of taste.

192mm, f4



135mm, f2.5



200mm, f4



138mm, f4



165mm, f4



155mm, f4



200mm, f4

[Mistral75]

If, indeed, the DA*60-250 ever reaches a true 250mm, it's at infinity only...

The fives examples in the patent have an upper focal length between 242.22mm and 242.95mm:

Telephoto zoom lens system

[WorksAsIntended]

Subject isolation of the 60-250 at effective 135/4 is the same as a 50 mm f1.5... that is a very classic more than good enough.

Vast groups of photographers use 70-200 lenses at 200 mm to do portraits, so the alleged „flat“ perspective seems really just your personal taste issue.

---------- Post added 2nd Feb 2020 at 20:56 ----------



Thats the norm for modern lenses though and applies to primes as well.

I just recently learned that at least some primes actially focus by doing nothing else than change focal length. So basically they are not even fitting to my old childish view on what a „prime“ is.

The tele portrait "issue" is a well discussed topic for many decades. Not just my personal view, but there are of course a lot of people that like tele portrait and both opinions are perfectly fine.

Your calculation about dof is wrong, you seem to ignore the difference in object distance for sensor filling heads / bodies.

---------- Post added 02-02-20 at 02:12 PM ----------

He may be true also. There are a number of factors that can give different results, including copy variations of the lenses.



These are 2 examples, the one from the top being the image of my friend, taken with 85mm f1.2L lens on a full frame, at f2. On the bottom it's my image taken at 150mm, f4 (with 70-200mm f4 lens on a full frame). He was shooting from the ground level and he used a gold reflector to bounce the light. I was shooting from the eye level from behind my friend and a little on his left. I used a white reflector because I liked her tan. If I wanted to get similar shot as my friend, I would have used the gold reflector, back up a little to use 180mm instead of 150mm and I would have lowered also my camera. But subject isolation wasn't a problem for me with a 70-200mm f4 lens even shooting next to a guy with an 85mm f1.2 lens.





I shoot portraits with any lens, depending on the available space I have on location. I wouldn't call the below images being flat in terms of perspective due to the fact that were taken with focal lengths longer than 105mm, but I think it's a matter of taste.

192mm, f4



135mm, f2.5



200mm, f4



138mm, f4



165mm, f4



155mm, f4



200mm, f4

Some nice shots. No arguing that it is possible to get enough isolation at 135/4, just not enough for every situation and that would be different with 250 f4. All I ment to sa was that it can be an issue in some situations not being makro.

[beholder3]

Your calculation about dof is wrong, you seem to ignore the difference in object distance for sensor filling heads / bodies.

And where did I write anything about dof? I was talking about subject separation. Unless you want to cherry pick special scenarios, subject isolation only depends on absolute lens opening, obviously.

[Dan Rentea]

Your calculation about dof is wrong, you seem to ignore the difference in object distance for sensor filling heads / bodies.

I don't think he was talking about small DOF at f1.5. He was talking about subject isolation and you will have a pretty good formula to calculate it.

85mm f1.8 lens: 85/1.8 = 47,22mm
200mm f4 lens at 200mm f4: 200/4 = 50mm

Here is an example from the training material that my photography teacher used years ago for making us understand how you can get similar subject isolation with cheap lenses as long as you have enough space for the tele lens.

Some nice shots. No arguing that it is possible to get enough isolation at 135/4, just not enough for every situation and that would be different with 250 f4. All I ment to sa was that it can be an issue in some situations not being makro.

As I said, as long as you have available space on location and you know how to position the model, a cheap 70-300mm lens can give you a better subject isolation than an 85mm lens. The main reason I shoot with fast lenses is related more to available light which can become problematic at indoor events where you shoot at f1.8 and ISO 3200.

[wed7]

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

Well, Pentax again can rebrand Tamron's F1.8 or 2.8 primes.

[interested_observer]

I have finally waded through 51 pages - and you guys are up to page 59. I'm getting there as fast as I can....

I guess Ricoh guys know how to select a lens better than me. They eventually have an optical test bench to measure lenses that I don't even have. So far, the 15-30 and 24-70 are no slouch. In fact , there are a number of reviewers said those Tamy are as good as or outclass some of the Canikon own lenses. Ricoh haven't chosen the cheapo Tamron for the K1, they'd chosen to rebardge only the best of the Tamron zoom lenses. Honestly, if a third party lens design was as good as the one from leading brands, I would even bother designing my own at the risk of it not being as good. The funny thing is the complain about a lens being originally designed by Tamron.. do you want the Tamron glass with lightning fast AF motor (and cost of development mostly paid by customers of other brands), or you want a Pentax own design with slow AF motor at double the price?

Pentax (under Hoya) retired one of their more notable optical engineers, Mr. Jun Hirokawa - who has quite a few of the current Pentax lenses to his credit. He was also the developer of the 3 legendary Limited series - the 31, 43 and 77. After Pentax (Hoya) retired him, where did he go? Tamron It's rumored that he was the lead designer for the Tamron SP 24-70mm f/2.8 and probably at least touched the 15-30/2.8 and 70-200/2.8. So, if you were Pentax, bringing out your first full frame camera body, and in need of lenses - your first decision is make or buy, and if buy - buy from whom. Buying from a lens designer whom you know extremely well, probably made the buy decision pretty easy - and accelerated the K1 to market with 3 essential lenses that were absolutely required.

Bottom line is that it appears to have been a pretty sound decision. Also, from the Tamron point of view - hiring Hirokawa would have been an easy no-brainier decision. His reputation and experience in retrospect has brought in the Pentax business. Easily has paid for himself many times over.

• through the viewfinder: Known and Unknown Pentax lens designers and their lenses

• Jun Hirakawa - Wikipedia

Also, scrolling through the various lenses that Hirokawa has designed, there are the FA 70-200mm f/4-5.6 and the FA* 80-200mm f/2.8, plus he was very familiar with the Pentax coatings - up till he was retired. So, my guess is that the Tamron 70-200/f4 probably has a lot of his finger prints all over the design to some degree.

---

Last edited by interested_observer; 02-02-2020 at 10:34 PM.

[Ian Stuart Forsyth]

Tamron 70-200/f4 probably has a lot of his finger prints all over

I hope not as I don't like cleaning fingerprints off the lens, But I do hope some of his heart and soul is found in the lens

One of his lenses I loved was the FA* 85 1.4 second would be the DA 55

[Sandy Hancock]

He was also the developer of the 3 legendary Limited series - the 31, 43 and 77.

Small point of order: Hirakawa did not design the FA 31/1.8 Limited. His design was rejected in favour of Ito and Murata's faster but larger design.

[Mistral75]

Second small point of order: Jun Hirakawa having designed the Tamron SP 24-70mm f/2.8 Di USD is more than a rumour. He is the inventor according to the patent.

[DagT]

Years ago Tamron bought the Zenza Bronica medium format system and made some truly wonderful lenses for the line. I still use them and have no problems buying rebranded Pentax lenses made by Tamron. :-)

[Andrea K]

Second small point of order: Jun Hirakawa having designed the Tamron SP 24-70mm f/2.8 Di USD is more than a rumour. He is the inventor according to the patent.

Then now we need to find the patent of the Tamron 70 - 210 f/4.0

[pres589]

Small point of order: Hirakawa did not design the FA 31/1.8 Limited. His design was rejected in favour of Ito and Murata's faster but larger design.

How do you folks know this stuff? Not doubt the accuracy. Is there a decent web resource for such information? Also sometimes I've been interested in knowing the general design goals for a lens; it would be interesting to know that as well although I'm sure that many lenses never had that information leaked about them.

[Mistral75]

How do you folks know this stuff? Not doubt the accuracy. Is there a decent web resource for such information? Also sometimes I've been interested in knowing the general design goals for a lens; it would be interesting to know that as well although I'm sure that many lenses never had that information leaked about them.

Patents are the primary source. Here a recap:

through the viewfinder: Known and Unknown Pentax lens designers and their lenses

[house]

How do you folks know this stuff? Not doubt the accuracy. Is there a decent web resource for such information? Also sometimes I've been interested in knowing the general design goals for a lens; it would be interesting to know that as well although I'm sure that many lenses never had that information leaked about them.

I would apppreciate more info regarding design goals at the launch of new lenses. Problem is that it gets mixed up with marketing speak.