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04-18-2013, 11:20 AM   #1
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f2.8 vs. f4

It used to be that the best (35mm format) lenses were at least f2.8 and sometimes faster. Those lenses had the best build quality, the best glass, the best features. And, in the time when low-light capability was weak, the faster the lens, the better. Of course, aperture is also about depth-of-field and not merely light control, but many photographers do not need extremely narrow DOF for most purposes.

Times have changed. My K-5 takes good photos in very low light, especially paired with modern image-editing programs.

Can manufacturers now produce f4 lenses that are top quality in build, glass, and features? If so, can most photographers who needed f2.8 lenses in the past now function well with f4 lenses? Would the shift to f4 lenses make them much less expensive than f2.8 lenses, even if f4 lenses were top quality?

What are the issues involved in making fast, good lenses these days?

04-18-2013, 11:36 AM   #2
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I'm not sure if I can answer the part about if manufacturers can make really really good F/4.0 lenses, but I can say that unless there is a serious penalty of cost, I would still prefer the F/2.8 lens over the F/4.0 lens. Not because I really need F/2.8 but because it's there if I need it. One of the reasons I chose a DSLR instead of a good bridge camera was the flexibility of a DSLR. Just because I don't necessarily need F/2.8 doesn't mean I might not want to use it in certain circumstances. If the price different between two equally good lenses; one F/2.8 and one F/4.0 is 10% or less I'll get the F/2.8 every time. If it's more than 25% I'd probably get the F/4.0, From 10% to 25% it would depend on an number of different factors.

NaCl(choice is the key)H2O
04-18-2013, 11:38 AM   #3
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There are top notch F4 lenses out there. The Canon 70-200 f4, the Pentax DA 60-250 F4, DA 15 Limited, DA 12-24, DA 17-70 F4.

Price-wise, the Canon 70-200 F4 is a good lens to use to compare, as it is pretty much half the price of the F2.8. It's also smaller, and lighter. It would be nice to have more F4 options, but I think we're pretty covered for that.

And to think about it more, Pentax's Limited Primes are not known for speed. The DA 21 F3.2, DA 40 F2.8, and DA 70 F2.4 are all slower than their previous brethrens (well, except the DA 40). This made them much smaller (as well as their APS-C circle) and cheaper than their FA brethrens.
04-18-2013, 11:49 AM   #4
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I would hope that manufacturers could (and would) make top notch f4 lenses (primes and fixed-aperture zooms) that would be significantly less expensive than corresponding f2.8s and smaller and lighter than corresponding f2.8s. But hopes are one thing; realities might be another.

04-18-2013, 12:07 PM   #5
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As mentioned above, there are quality lenses available at f4. I have the 60-250 and the 12-24 and love them both...but...I still want 2.8 if it is available. As a wedding shooter, I am not always allowed to use flash so a 2.8 is a must have. Yeah, you can crank up ISO, but sometimes I have to shoot high ISO and wide open to get the job done.

I guess that ideally, they could be offering both at a high quality to meet the needs of more consumers. I think the issue there is just having too much offered at the same time. It is one thing for Canikon to do that, but they can because of their size. I am not sure that it would be a good move for Pentax unless they suddenly start gaining much more market share.
04-18-2013, 12:26 PM   #6
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QuoteOriginally posted by sholtzma Quote
Can manufacturers now produce f4 lenses that are top quality in build, glass, and features?
Yes - DA*300 f/4 and the Sigma 100~300 f/4 are 2 top quality feature rich f/4 lenses.

QuoteOriginally posted by sholtzma Quote
If so, can most photographers who needed f2.8 lenses in the past now function well with f4 lenses?
Absolutely Not!!! Many may think different but there is more to it than just the extra speed or loss of extra speed. Dynamic Range loss is one issue when dealing with extra stops of ISO (speed matching f/2.8 and f/4) and DOF is another, and not to mention a little extra speed TTL (in the form of true light) for a cameras AF modules.
04-18-2013, 12:28 PM   #7
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I don't shoot weddings, but I too have been in plenty of situations in which I had to shoot at high ISOs and wide open apertures. Of course, I do not dare shoot at anything over ISO 6400, and I try to stay far from that if I can. Naturally, if we could shoot at ISO 52,000 or 104,000 with little noise, accurate color, and good contrast, that would reduce the need for a 2.8.

My question is, can manufacturers produce (if they wanted to) an f4 lens with the same top notch quality in glass, build, and features that f2.8 lenses have traditionally had? And if they can, would those lenses be less expensive, lighter, and smaller?

For example, I have the 12-24, and it is a nice lens. Would an f2.8 lens in roughly that zoom range be significantly better? Need it be better?

If sensor and processing performance continues to improve, will we need f2.8 lenses? With the growth in "enthusiast"-class shooters, would there be a sufficient market for a top notch f4 lens, even if an equally top notch f2.8 were needed for pros?
04-18-2013, 12:33 PM   #8
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QuoteOriginally posted by sholtzma Quote
My question is, can manufacturers produce (if they wanted to) an f4 lens with the same top notch quality in glass, build, and features that f2.8 lenses have traditionally had? And if they can, would those lenses be less expensive, lighter, and smaller?
Yes they can. It's only a question of: do they have the production abilities to make both the F2.8 and the F4 lenses.

QuoteQuote:
For example, I have the 12-24, and it is a nice lens. Would an f2.8 lens in roughly that zoom range be significantly better? Need it be better?
It'd be quite a lot larger and heavier. It wouldn't necessarily be sharper.

QuoteQuote:
If sensor and processing performance continues to improve, will we need f2.8 lenses? With the growth in "enthusiast"-class shooters, would there be a sufficient market for a top notch f4 lens, even if an equally top notch f2.8 were needed for pros?
Yes - we would still need F2.8 lenses. For example, we still use F1.2, and F1.4 primes. As such, F2.8 is still tremendously slow compared to those lenses.

04-18-2013, 12:42 PM - 1 Like   #9
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QuoteOriginally posted by sholtzma Quote
photographers who needed f2.8 lenses in the past now function well with f4 lenses
You also need to remember lenses usually perform a little better when the stopped down.

So F2.8 should perform better at F4.0 than an F4.0 wide open.
04-18-2013, 01:00 PM   #10
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QuoteOriginally posted by joe.penn Quote
...and not to mention a little extra speed TTL (in the form of true light) for a cameras AF modules.
Most AF sensors will not benefit from lenses faster than f/5.6.

The K-5 II(s) is the first Pentax DSLR model that has one f/2.8 centre AF sensor.
04-18-2013, 01:36 PM   #11
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QuoteOriginally posted by JinDesu Quote
Price-wise, the Canon 70-200 F4 is a good lens to use to compare, as it is pretty much half the price of the F2.8. It's also smaller, and lighter. It would be nice to have more F4 options, but I think we're pretty covered for that.
I'd be interested in top-quality F4 zooms for half price which are smaller and lighter. Take for instance the DA* 16-85mm on the roadmap. If it's f/2.8 I likely can't afford/justify it, plus it might be too bulky to be my general "walking around" lens that I keep on the camera all the time.

But if it's f/4 then I probably CAN get it and use it regularly. It might end up replacing my 18-135mm WR (DA* is weather resistant too) and even though it's shorter I can use the 55-300mm to cover the long end and still have a little bit of overlap between them.

The DA 17-70 is possible, but I really prefer for my everyday lens to be weather resistant if possible. Nor would I really want a 28-70 (or 75 or whatever) no matter how good it way because it loses too much wide angle.
04-18-2013, 01:39 PM   #12
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QuoteOriginally posted by dboeren Quote
I'd be interested in top-quality F4 zooms for half price which are smaller and lighter. Take for instance the DA* 16-85mm on the roadmap. If it's f/2.8 I likely can't afford/justify it, plus it might be too bulky to be my general "walking around" lens that I keep on the camera all the time.

But if it's f/4 then I probably CAN get it and use it regularly. It might end up replacing my 18-135mm WR (DA* is weather resistant too) and even though it's shorter I can use the 55-300mm to cover the long end and still have a little bit of overlap between them.

The DA 17-70 is possible, but I really prefer for my everyday lens to be weather resistant if possible. Nor would I really want a 28-70 (or 75 or whatever) no matter how good it way because it loses too much wide angle.
The problem is, the flagship DA*18-85 shouldn't be F4, in my opinion. It should be F2.8-F4, and be plenty sharp wide open. It would be nice if they reintroduced the DA 17-70 as WR separately.
04-18-2013, 02:10 PM   #13
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QuoteOriginally posted by JinDesu Quote
The problem is, the flagship DA*18-85 shouldn't be F4, in my opinion. It should be F2.8-F4, and be plenty sharp wide open. It would be nice if they reintroduced the DA 17-70 as WR separately.
Star lenses don't have variable apertures How about compromising at F3.5?

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04-18-2013, 02:11 PM   #14
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QuoteOriginally posted by Adam Quote
Star lenses don't have variable apertures How about compromising at F3.5?
Pffft.. 3.2!
04-18-2013, 02:34 PM   #15
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The FA 20-35/4 seemed to do very well,
and it may get reincarnated as the DA Limited zoom on the road-map.
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