A Plea for a 17.5 f2.8 Lens for Olympus Four Thirds DSLR

[haziz]

A 17.5 (or 17 or 18 even a 20 mm) f2.8 lens would be a sweet "walkaround" lens. They can even make it an f3.5 lens if that makes it more

compact. You will immediately get requests for something even wider, though personally I would prefer a 17.5 mm rather than a wider lens

as a walkaround lens. A 14 mm and a 42 (or 50) mm lens could be added later as other primes. The 42 mm (or 50 mm) should be fast (at

least f1.8 preferably f1.4, even f1.2) to make it an ideal portrait lens. I do believe that a 50 (or 42 mm) mm f1.4 should be added as a

portrait lens. The 50 f2 lens probably makes too many compromises with a long helical to allow it's use for macros. Moreover since there is

a rich heritage of normal lenses for 35 mm cameras, they can probably design a 50 mm f1.4 lens in their sleep.

 

Pentax can make a pancake 21 mm lens f3.2 lens so we know that a 20-21 mm pancake is doable. Olympus's 40 mm f2 pancake for the

OM mount is sweet. My OM2SP with the 35 mm f2.8 (less often the 40 mm pancake or 50 mm f1.4) is usually what I grab when I walk out

wanting to take a few quick snaps. I do have some other fancier set ups including both Leica M and R as well as Canon digital but it is

usually the Olympus OM that I grab as I am heading out. Since I got the E-420 it has been my grab and go camera, we'll see if this

continues or I return to the Olympus OM.

 

Thanks.

 

Sincerely,

 

Hany.

[emraphoto]

i second that plea. i looked long and hard at the e-420. it was everything i wanted for documentary work. small, great

performance and affordable (should i happen to "lose" one while working).

it was the lack of compact and reasonably wide (after the lens crop effect) lenses that killed it for me. i'll keep watching

though... the e-420, 25mm pancake and an 18mm pancake? i'd buy.

[mrraz]

Hey guys, There is no crop factor for four-thirds lenses. They are all 2x equivalents of 35mm cameras; 14mm = 28mm, 42mm = 84mm. The normal lens would be a 25mm, and if memory serves me right, the new pancake is f/2.8 25mm. It would seem to fit the bill for both of you. Btw, Sigma makes a 30mm f/1.4.

 

However, I can't see how you can fault the 14-42mm zoom except for the f/stop. It's a very compact lens. My wife has on one of her 410 bodies. It's less then half as big as my 14-45mm that came with my E-500.

[john_robison3]

Yeah, that would be sweet. I think the problem is the 38+mm flange to sensor distance that would make any 17mm lens a retrofocus design. But, as you point out, Pentax seems to be able to make a small 21mm and the K-mount flange is about 46mm from the sensor. I just purchased my first DSLR, an E300 and it feels huge compared to my OM-1s. I don't have any ED lenses for it yet but the 24mm f2.8 Zuiko for my OM seems to be working fine so far. The E300 seems to be the red headed stepchild of Olympus DSLRs, not too popular and therefore cheap.

[haziz]

In response to Glenn Rasmussen: I do have the 25 mm f2.8 pancake lens which is normal for Four thirds format. I am just hoping for a relatively compact prime lens with a field of view similar to a 35 mm lens on 135 film format hence my dreaming of a 17.5 mm lens give or take 1 to 2 mm.

 

Thanks.

 

Sincerely,

 

Hany.

[michael j hoffman]

Yes, indeed!

 

I would love to see an Olympus ZD compact fixed focal length lens in the 14mm to 19mm range, make it an f/2.8 and very compact. If Olympus is going to entertain this idea, I expect we'll see a 17mm lens first, then maybe a 14mm and/or a 21mm to follow.

 

Michael J Hoffman

[patrick j dempsey]

There are extreme design limitations to the 4/3s mount being that the mount is 1.5 times longer than the sensor diagonal. Due to this limit, the 25mm f/2.8 is going to be the fastest, most compact normal lens you are probably ever going to see for 4/3s. They could easily make some fast and compact longer lenses, like an f/2(or better) 35mm lens. The 4/3s mount concept is an extreme lens design challenge and is in many ways opposite of the OM mount concept which was specifically designed to allow for a slew of compact wide and normal lenses. The 4/3s mount was designed with digital imaging quality in mind... the relatively long mount assures that the angle of light leaving the lens and hitting the sensor is fairly low, as opposed to a narrow mount which would encourage designs with a higher angle of attack, causing issues with the sensor.

 

I may be wrong, but it is my opinion that you are never going to see the kinds of compact wide lenses for 4/3s that you have for OM mount.... simply because this was not a consideration of the original design strategy.

[godfrey]

<center>

<img src="http://homepage.mac.com/godders/109-hinge.jpg"><br>

<i>Panasonic L1 + Olympus ZD 25mm f/2.8</i><br>

</center><br>

I would love a 20mm f/2 or f/2.8. And 18 would do well too, and an f/3.5 would be fine ... I'm not picky. At present the ZD

25/2.8 and Leica 25/1.4 are my favorite lenses, a little shorter and similar qualities would be a delight.

<br><br>

Godfrey

<br>

[skip_williams]

Patrick,

 

Why is the deep mount a barrier to fast lenses? I don't understand? Leica's been able to do it with a 25/1.4 for a normal lens. Why couldn't a similar lens be designed as a 17/2.0 or some other moderate, fast WA?

 

Skip

[godfrey]

When a lens focal length is shorter than the mount register, an inverse telephoto optical design must be used in order to

move the primary nodal point closer to the image plane than the lens optics. This provides clearance for the operation of

the mirror in an SLR. With retrofocus designs, the issues that come up are size, weight and complexity (and cost!) to

obtain low distortion, high quality imaging with an ultra high speed design.

 

Leica's excellent Summilux-D 25mm f/1.4 ASPH is a beautiful lens ...but it is quite expensive, it weighs over a pound and

is nearly as large as the pro-class 14-50mm f/2.8-3.5 zoom lenses. Pentax has built a similar very high performance

design in their SMC Pentax-DA 14mm f/2.8 lens ... note that it's two stops slower! ... that weighs about the same, is about

the same size, and costs about the same too. The problem of producing speed with shorter focal lengths continually

increases cost and package size.

 

In essence, you can't get something for nothing when it comes to the physics of optical design. A compact and light

20mm focal length lens to cover the 4/3 can be made for sure ... witness the Pentax DA21 Limites ... but only at the cost

of speed ... that Pentax lens is f/3.2 maximum aperture, not f/2.

 

I would be perfectly willing to go with an 18 to 20 mm lens with a maximum aperture in the f/2.8 to f/3.5 range. f/2 will

make it a large, heavy and much more expensive lens ... I might be willing to buy it for that speed, but it is a tradeoff.

 

Godfrey

[patrick j dempsey]

What Godfrey said. Consider that the 4/3s mount itself is 37mm long, with a (true) normal focal length lens of

22mm. The Olympus Pen F half frame camera (which had a film plane the same size as an APSC sensor) was a 27mm

long mount with a true normal focal length of 30mm. Many 35mm full frame cameras had a mount around 45mm long

with a true normal focal length of 43mm. The simple fact that the lens mount is 1.7 times longer than the true

normal focal length is the basic problem with fast compact wide lenses.

 

So why not look at your OM zuiko lenses as a clue to what might be possible? You can't really look at the 40mm

f/2... that is a portrait lens for 4/3s! The design equivalent in terms of lens mount length (not view angle

equivalent) to a 17mm lens for 4/3s would be the 21mm for OM. (4/3s mount 37mm:17mm = OM mount 46mm:21mm) And

what we see is two different 21mm lenses... the f/3.5 which is similar in size to the compact 24mm f/2.8 OM...

which I'm guessing the 25mm f/2.8 ZD is based on... and the f/2 which is dramatically larger and weighs much much

more. (Not as much as the Leica 25mm f/1.4, but still big comparitively) But this also brings up another lens

design.... the 16mm f/3.5 OM... which is also similar is in size to the 21mm f/3.5 and 24mm f/2.8. If you do the

math... OM mount 46mm:16mm = 4/3s mount 37mm:13mm!

 

So... it might technically be possible for Olympus to release a 13mm f/3.5 wide-angle pancake lens, as well as a

17mm f/3.5 pancake lens... but would Olympus be willing to sell them for cheap enough to make such a slow

fixed-lens design marketable?

[patrick j dempsey]

Ok, I went and looked at some numbers... the new pancake ZD is 25mm f/2.8 with a length of 23.5mm. Now I'm going

to do some big time assumption. The following numbers are totally theorhetical and based on nothing in the

reality of lens design. It is based on the assumption of SCALING down existing OM Zuiko designs to the 4/3s

mount. I looked up actual numbers, so this corrects some of the things I said in the previous post. Bear with me

as I go off into theorhetical land:

<br><br>

OM mount registration distance: 46mm<br>

4/3s mount registration distance: 38.7mm<br>

Scale factor: 1.189

<br><br>

Here are the OM wide angle lenses from 16mm to 28mm scaled down to 4/3s mount. Focal length, maximum aperture

and physical length of the lens from mount to filter are listed, as well as full frame equivalency:

<br><br>

16mm f/3.5, 31mm -> 13.5mm f/3.5, 26mm = 27mm FFEq<br>

18mm f/3.5, 42mm -> 15mm f/3.5, 35.3mm = 30mm FFEq<br>

21mm f/2, 44mm -> 17.7mm f/2, 37mm = 35.4mm FFEq<br>

21mm f/3.5, 31mm -> 17.7mm f/3.5, 26mm = 35.4mm FFEq<br>

24mm f/2, 48mm -> 20mm f/2, 40.4mm = 40mm FFEq<br>

24mm f/2.8, 31mm -> 20mm f/2.8, 26mm = 40mm FFEq<br>

28mm f/2, 43mm -> 23.5mm f/2, 36mm = 47mm FFEq<br>

28mm f/2.8, 32mm -> 23.5mm f/2.8, 27mm = 47mm FFEq<br>

28mm f/3.5, 31mm -> 23.5mm f/3.5, 26mm = 47mm FFEq<br>

<br><br>

So based on these estimations, scaled down versions of OM lens designs could produce a handful of compact wides

and normals... and even a rather fast 18mm lens! Hmm... I might have to eat my words! And really the designs

would not have to be as complex because they would be covering a smaller image circle.

[godfrey]

These older film camera lenses are not designed with digital sensors' sensitivities in mind. Digital sensors are critical on

angle of incidence of the light ... film is not ... and this becomes particularly critical as the focal length decreases.

 

Digital sensors require that the light be incident to the photosites at very nearly orthogonal angles (very close to 90

degrees to the sensor plane) for best results. Without that, artifacts, chromatic aberration, corner shading, loss of sharpness and light

falloff arise.

 

This is yet another factor contributing to the difficulty of producing short focal length lenses that are fast, compact, light

and inexpensive. Results with film camera lenses onto digital sensors, for lenses under 20mm focal length, have been

only mediocre despite the smaller format size for this reason.

 

Godfrey

[jtk]

Pentax 14/2.8 is big and exquisite, 20/3.2 is tiny and exquisite. Take your pick.

[jtk]

...make that 21/3.2. Sweet, fast low light autofocus (but it's as good as any manual focus lens, used that way).

[warren_lafever]

i recently wrote olympus about a wide prime 12,14mm - f1.4,2 and they sent me a we cant talk about projects in development email. so i assume one is on the way of some sort

[mark_audacity_romberg]

They can make a 12mm zoom; it follows that they can make a prime at a similar focal length. <br>

The 'no lenses shorter than the register' arguments above <i>sound</i> good, but the fact that there are several such

lenses in production makes them not only invalid, but a little silly.

[warren_lafever]

here is another thought. see if you can find some really wide and fast OM lenses and use those with an adapter.