Zuiko 28mm f2.8 on Sony a7r: Is this what I should expect?

diddy · Joined: 28 Mar 2012 Posts: 288

Hi,
I read a few reviews about the Zuiko 28mm f2.8 lens on the Sony a7r and they were all quite positive. So I though I should give it a go. This is one picture where I managed to get the building in the distance in focus using the focus magnifier function, however, the borders are quite weak. Is this what I should expect from this lens or do I just have a bad copy?
Here the picture (Please have a look at it at 100%):

marcusBMG · Joined: 07 Dec 2012 Posts: 1304 Location: Conwy N Wales

What f stop was this?

For more insight have a look at Dan Eurrit's field curvature tests here

http://www.codectest.com/2014/28mm-camera-lens-comparison-on-the-sony-a7r-first-round

http://www.codectest.com/2014/28mm-prime-lens-comparison-shot-on-sony-a7r-second-round

calvin83 · Joined: 12 Apr 2009 Posts: 7554 Location: Hong Kong

Which aperture value you use? F8 or F11?

diddy · Joined: 28 Mar 2012 Posts: 288

I am not too sure any more. Most of my pictures were taken with either f8 or f11. If this were one is f8, do you think that f11 could improve performance by that much?

calvin83 · Joined: 12 Apr 2009 Posts: 7554 Location: Hong Kong

Most old wide angle are not as flat field as the recent ones made specifically for digital sensor. In your photo, I think only the building in the center is in focus. Assume the lens and adapter is fine, you may need to re-focus/adjust the orientation of camera if you want the trees on the left/right to be in focus. You might need to use F11 if you need sharp extreme corners.

diddy · Joined: 28 Mar 2012 Posts: 288

Thanks for your reply. I had a look at the other pics I took and non really shows great corner performance (and there were some f11 pics among them). It seems like it might make sense to start saving money for the Sony FE 28mm f2 lens which will be released in March.

memetph · Joined: 01 Dec 2013 Posts: 942 Location: Poland

What was your focusing point ?
You should test your lens by shooting a wall or a facade from a distance.

shapencolour · Joined: 03 Oct 2013 Posts: 270

The picture looks much,much too soft for the Oly 28/2.8 on the A7/R at f8-11.Normaly picture should be sharp/very sharp across the frame with only some smeraing in the farthest corners at f8,that is almost entirely gone by f11.You probably have either misfocused or there is something wrong with your adapter.Badly assembled copy is also possible.

memetph · Joined: 01 Dec 2013 Posts: 942 Location: Poland

If the problem is your lens , you could try the Rokkor MD W 28 3.5 ( 5 elements) which is good and pretty inexpensive or the Pentax SMC K (not M) 28 3.5 which is very good and still affordable.
The future Sony has the advantage that it can be transformed in a UWA. Let's wait for its performance.

SMC K 28 3.5 on A7

diddy · Joined: 28 Mar 2012 Posts: 288

@memetph: The focus was on the temple in the centre. But at this distance, everything should be in focus (well at least everything on the same line as the temple and beyond).

@shapencolour: The building in the centre is sharp though. What I realised is that if I position the focusing ring on the infinity mark, the borders get sharp, but the building/temple will be unsharp. So I used focus magnification to focus properly on the temple: On the focusing scale this is slightly before the infinity mark. I asked in another forum about this and someone mentioned that the field curvature might be the problem.
Example:

View at 100%. You will see that the fence gets unsharp towards the centre as well as the temple etc.

Pictures taken of closer objects do not show any problems. Do you have any examples of this lens at f8 or f11 that you can share? I still have the option to return this lens for a refund in case you think it is a problem with the lens itself.

memetph · Joined: 01 Dec 2013 Posts: 942 Location: Poland

it is normal that inifinity will be reached before the symbol. The adapter has to be slightly too short to secure that.

diddy · Joined: 28 Mar 2012 Posts: 288

@memetph: Ok, thanks for clarifying this. So do you think the lens has a problem then?

RSalles · Posted: Sun Dec 14, 2014 7:32 pm Post subject:

OM Zuiko series has 2 lens that I have opposite impression: the 1.4 50mm is one of the lens I like the most, the 2.8/28mm is a lens that I don't like.
Last year I bought a copy from a member here and I had to happinesses: The first when buying and the second selling. It was the worst Zuiko I had by far,

Cheers,

Renato

memetph · Joined: 01 Dec 2013 Posts: 942 Location: Poland

Gerald · Joined: 25 Mar 2014 Posts: 1196 Location: Brazil

A 36 MB FF sensor is cruel and shows all the shortcomings of a wide-angle lens.
First the indisputable fact: There is indeed a very visible difference in sharpness between center and edge. This kind of behavior is common in photographic lenses, especially wide-open. However, the real question is how to make a correct diagnosis of the situation.

There are five hypotheses to be tested:
1) The difference in sharpness between center and edge is caused by coma and astigmatism.
2) The difference in sharpness between center and edge is caused by field curvature.
3) The adapter or lens/camera mount suffer from tilt.
4) This behavior is normal for this lens
5) The copy of the lens is defective.

To find out which is the true hypothesis, it is necessary to retest the lens properly. Please, start by noting what was the aperture used!
Any lens must be tested wide-open first. It is incredible, but many people do not know that any minimally decent lens has an excellent performance at F8-F11 wide-open. Testing a lens at F8-F11 is pretty much a waste of time.

diddy · Joined: 28 Mar 2012 Posts: 288

Ok, here are my test results in following order: f2.8, f11, f11. The picture of the the building seems fairly ok, but the one of distant trees/bushes shows a weakness outside the centre (some legacy lenses do exhibit this behaviour - not too sure if this is normal for the Zuiko):

scsambrook · Expire: 2011-11-18

Diddy - I just downloaded your images spent a few minutes playing with them in my lunch break here at the office. If I open them in Picasa they actually look quite a bit better than they do on the forum. If I add a very modest amount of sharpening they look better still.

The trees right at the edges of the shots with the white house actually look pretty good to me.

To be truthful, going by what I can see on my screen, I'm not sure that I can see anything to complain about in this particular lens. Most - if not all - 28mm lenses show some fall-off at the edges and the effects of diffraction can also be expected to reduce clarity a little at f11. I don't want to sound unkind or grumpy, but just how much more detail do you want to get out of those tree branches? There's plenty of informed writing about how fine detail at long distances gets 'lost', particularly with wide angle lenses. I wonder if you're running into the proverbial brick wall here. How does it perform at distances between 1 meter and - say- 20 meters?

diddy · Joined: 28 Mar 2012 Posts: 288

From what I can judge by my testing, at closer distances this lens performs better.
In general, it is good to hear that you mention that this it what I can expect from this lens (judging by the picture with the trees in the distance). Honestly I wouldn't have expected much more, maybe just a tiny bit because reviews on this particular lens on the Sony a7r were quite positive. On the other hand, I tested a lot of legacy wide angle lenses on the Sigma SD1 Merrill (although this one has a crop-sized sensor) and of have the lenses showed a similar effect. I didn't have the Olympus Zuiko 28mm f2.8 at that time. Overall, yes, judging by the GBP 39 I paid for it, it does a fairly ok job on the Sony a7r.

Gerald · Joined: 25 Mar 2014 Posts: 1196 Location: Brazil

Tervueren · Expire: 2014-11-08

https://www.onlandscape.co.uk/2014/02/wideangle-options-sony-a7r/

diddy · Joined: 28 Mar 2012 Posts: 288

Thanks a lot for the links to these articles!

shapencolour · Joined: 03 Oct 2013 Posts: 270

To my eyes both the 2.8 and f11 pictures of the building look more or less as they should.I don't see the mentioned weakness either.I see them now on the lousy desktop's screen,but for sure their appearance would be better in the LR5.7 with default settings and very good after applying a little bit of sharpness and custom CA correction.