[pathdoc]

You hear the phrase used, but what does it mean?

Back in the day, it was accepted that a prime lens was better than a zoom lens - that gap has now closed significantly, and if you're willing to pay enough then I'm sure you can find zooms which are better at any FL than a competently built consumer prime at that same FL.

Back in the day, a K mount prime typically carried a wider maximum aperture than a zoom. Some of the Takumars were relatively slow, e.g. the 28mm f/3.5 and the 135mm f/3.5 version) while these days, some of the limiteds (especially the DA15/4.0) are also on the sluggish side, although it has to be acknowledged that their slower apertures are a deliberate sacrifice in the interest of compactness on the APS-C format.

SO it seems to me that a good rule-of-thumb definition of a "stack of primes" zoom is one which...

a) Has image quality at least equal to a consumer-level prime of approximately equal vintage from the same manufacturer (e.g. no-one's asking it to outdo an FA Limited or * prime, although it's a bonus if it does, and it's not fair to pit yesterday's lens formulae and coatings against today's). IQ to be judged on the basis of sharpness, resolution, resistance to CA and flare, minimal or easily correctable distortion, but NOT Bokeh, as this is IMO more a matter of individual taste.

b) Has a relatively fast maximum aperture, which it retains throughout the zoom range (f/2.8 seems a reasonable yardstick here, although f/3.5 might be acceptable if IQ is particularly good).

What are the thoughts of others? I'm not necessarily asking for candidate lenses (that's a direct road to the hell of heated arguments); I'm more interested in your views on criteria.

[vonBaloney]

IMO, when people use that phrase, it means nothing more than "this lens is very sharp and high-quality for a zoom" (i.e. why buy all those primes to cover the range, just use this), but it doesn't refer to anything in terms of distortion, bokeh, or flare. It *might* connotate having a relatively large max aperture (probably constant) for a zoom, but not sure about that. But then I've only ever heard the phrase applied to the Pentax-A 35-105/3.5, so maybe it just means that specific lens!

[pathdoc]

I've heard it applied to the Sigma 18-35/1.8, with good reason, and if only the AF didn't suck so much for some owners and for our forum testers it might have gone on to supplant the 35-105 in that regard.

[blackcloudbrew]

Yes, the A 35-105 comes immediately to mind with this phrase. I've owned two of them and it really is kinda like that. Given the age of the A35-105 primes were really much better in comparison to zooms, but the A 35-105 was different (and still is IMHO) and behaved...like a stack of primes. I think modern zooms have rendered this notation moot but the moniker remains for the A 35-105.

[jatrax]

I think the phrase originated back in the day, when primes were king. A zoom that was even close to prime quality was a surprise and notable. The F 35-70 has often been described that way. And using it there is a distinct difference between it and other zooms of that era. How much of that was marketing and how much truth is a different question.

But as you say a good high quality zoom is very comparable to a good prime these days, or at least the difference has shrunk so as to be almost unnoticeable for most.

[clackers]

The Canon 70-200 was a game-changer.

[Rondec]

I think people talk about a zoom that is decent wide open at a lot of different focal lengths. The DA *50-135 is described that way, but it is no where near as good at 77mm as the FA 77, for example.

[normhead]

You guys are completely missing the point.

The stack of primes is a zoom lens that exceeds primes through it's range....




There are just very few lenses with this type of centre and edge sharpness, zoom or prime in the 60-250 range and the little difference there is makes no practical difference, unless you want a faster lens. They and find any other pentax lens this close to excellent on the charts both centre and edge, all through it's range.

For example, compare the 60-250 at 135mm to the 70 macro... it's not too much of a stretch to speculate the 60-250 is probably better.


You could argue, the Canon 70-200 isn't any better over all, although the control of CA on the Canon is stellar for a zoom.

[pathdoc]

Sorry to seem ignorant, but can you please explain what the abbreviations MTF50 and LW/PH mean?

In the last chart/table, you compare the 60-250 at 135mm to the "70 Macro" (which company? I didn't think Pentax made one) and then there is a table listed at 100mm. Did you in fact mean the 100 WR Macro?

By your own definition, it seems that if you're going to compare a zoom to a prime, surely you need to at least make the comparison at the same focal length (and apertures where these are common), NOT the focal length and aperture which is most advantageous to the zoom.

In the end, the issue is which primes you are exceeding. There is a difference between being better than a DA50/1.8 and being better than the DA*55/1.4, isn't there? And it's probably not hard for even a run of the mill zoom lens of today to be better than a third-rate, third-party prime of yesteryear. There has to be some sort of yardstick, otherwise you're comparing apples and oranges.

One thing I will accept from your argument, and that is that it's probably only objective indices like this which enable any sort of comparison. Also, standardisation of testing is important, and it seems to me that not all testing authorities out there agree on the metrics!!

Ultimately there is that mysterious quality called "rendering", which I'm not sure we will ever be able to quantify, any more than we can hope to quantify any aspect of human art. And that's what stops us all from ending up with the same basic lens (or set thereof) on the same basic system. Which is no help at all for LBA sufferers, but it does keep things interesting.

[boriscleto]

In the last chart/table, you compare the 60-250 at 135mm to the "70 Macro" (which company?

Norm owns a Sigma 70mm macro. It is one of his go to lenses for comparison...

Sharpness: What is it and how is it measured? | imatest

Line pairs per millimeter (lp/mm) was the most common spatial frequency unit for film, but cycles/pixel (C/P) and line widths/picture height (LW/PH) are more convenient for digital sensors.

Experience has shown that the best indicators of image sharpness are the spatial frequencies where MTF is 50% of its low frequency value (MTF50) or 50% of its peak value (MTF50P).

[pepperberry farm]

in my short time on this forum, I've only seen two zooms referred to as 'stack of primes': the SMC A 35-105mm f3.5 and the SMC A 35-70mm (but which version, I'm not sure)...

I have a 35-105mm and it takes very nice pictures; while I agree that 'rendering' can be more subjective, especially since our idea of 'rendering' doesn't seem to jive with the standard definitions of the word...

I've always taken that a true rendering of color was essentially that the colors you see through the lense or in the image or on the print are the same colors that you would see if you saw the object in real life...

[UncleVanya]

My DA* 50-135 and my DA* 60-250 were very close to my A*85 - so close I couldn't tell you which one made each picture when shot at 85 f/8. At f/4 the 60-250 was a little easier to pick out despite excellent results.

[pathdoc]

Thanks for the clarification, boriscleto.

[.a.t.]

The Canon 70-200 was a game-changer.

Which model?

[ZombieArmy]

I've also seen "stack of primes" used for the 75-150mm M zoom, albeit not as much.