New to ICL cameras - primes - help

Hi all, I never actually joined the forums at DPreview but have used the site often over the years. Anyway, I thought I would join here.

I'm a newbie to ICL cameras having just got a used Olympus OMD E-M1 II. I got it for the Panasonic 100-400mm to hopefully improve my wildlife photography (mainly birds at the moment). Therefore, I currently have just one lens and don't have the funds yet for a decent shorter zoom. Having come from a small sensor bridge camera but with a decent lens, I'm wanting to invest in the better lenses to really make a worthwhile difference. This had me investigating a cheaper stop gap prime lens that I could still use for low light in the future and led me to dxomark (and others).

My main question is about the Olympus 45mm F1.8. It has excellent reviews but clicking this link, Dxomark Olympus 45mm F1.8 and then clicking 'Sharpness' and then 'Field Map' leads you to a set of images from 1.8 through to 22. Unfortunately, I can't link directly. Why at f2.8 would the lens suddenly degrade? I would expect a steady rise and fall in quality.

I've made a spreadsheet (half the fun) importing these dxo images of the less expensive primes from Olympus, Panasonic and Sigma and non of them impress me particularly (apart from the 75 f1.8 which is too expensive) when compared to the 12-40 F2.8 and the 60mm macro that looks ok (another wish of mine). To me, I thought that the whole point of a prime was to be decent through the range, good wide open and yet most seem to fail. Don't forget, I'm very new to this different lens stuff so maybe I expect too much, I'm also a pixel peeper lol.

Never rely on a single site that tests just a single sample of a lens. They might have got a defective lens, maybe it's normal sample variation, or some glitch during their testing or measured data processing.

Compare e.g. www.lenstip.com/316.4-Lens_review-Olympus_M.Zuiko_Digital_45_mm_f_1.8_Image_resolution.html

The answer to your question can actually be found at lensrentals (where 10 lens samples are measured and averaged):
"If your question is ‘how did it get sharper in the center, but softer in the edges when stopped down,’ well, the answer is it didn’t. This can happen when a lens has a lot of field curvature."

For the nitty-gritty details please read the blog entry at www.lensrentals.com/blog/2018/03/finally-some-more-m43-mtf-testing-are-the-40s-fabulous/

I guess you are referring to the edge sharpness of 45 I guess you are referring to the edge sharpness of 45 @f/2.8?

It is little strange since the field map showed the edge sharpness would be reduced then improved again on stopping down. It could either be the particular lens issue (sample variation) or it was a fault on DXOMark. As per the few lenses on my research, this doesn't happen.

This happened on some other lens review (e.g. the plastic fantastic O 40-150).

Next, the 12-40 f/2.8 is a very excellent lens. While it has similar center sharpness of the P12-35, it's edge performance is better especially around the wider apertures.

In fact, might be of the format characteristic enabling easier lens design, the prime lenses IQ (specially the center) might not have absolute advantage over zoom lenses. It is to say, the IQ of zoom lenses, specially those kit class f/3.5-XX zoom lenses from Panasonic, are not very far behind prime lenses. I would say not the M43 prime lenses bad, just the zoom lenses are outstanding.

Finally, when I look at the green zone of the field map of M43 lenses, I am impressed. Some of their edge could be not perfect, but M43 lenses have taken lens correction into part of their design. Not sure how much lens correction been taken into account by DXOMark.

DXOMark has offered great piece of info and on its multiple cameras testing allowing me to compare lenses directly. The down side is a few mistake been there without attention to and it has no more test on newer lenses...
Lens rental might not offer the level of info DXOMark can provided. I really wish there could be a site having all the goods from DXOMark, Lensrental and OpticalLimit...

Very interesting read thank you. As and aside, the 'Name Length vs Image Quality' graph made me chuckle. Yes, I have checked other reviews of the lens and they are generally positive, it was that image on DXO that jumped out at me and had me question what might be going on.

That certainly looks very strange.

The better zooms do seem to be especially good. I just need to be patient and save up. I'm aiming for either the Olympus 12-40mm F2.8 or 12-45mm F4 version. They cost the same used where I am.

Your mention of kit lenses reminds me of my observations when comparing the DXO images - I thought that for 14mm alone, the Olympus 14-42mm F3.5-5.6 was a cheaper and better option than the 17mm prime if you need wide angle. The 17mm is overpriced I think.

I like the way DXO present (or is that presented) their reviews, I find them the easiest to understand. I wish they had a review of the Olympus 25mm 1.7 in fact, so that I could see how that looks from their perspective.

My opinion of a "portrait prime" is that it isn't all about sharpness. It is about how it renders, both in the center and corners. Even how it renders the out of focus areas. You don't always want pure sharpness in a portrait. How many people do you know that have tack smooth skin?

The Oly 45mm f/1.8 gets a lot of great marks because it is small, it is light, it is very good at optical quality, and more. And it isn't $1000 US. People get this for what it is, and they use it, and if they don't like the optics, they can bump up to the 45mm f/1.2 Pro...

Agreed. The 75/1.8 has a reputation for being amazingly sharp, but imo it's actually too sharp for portraiture - if I use it in that context, I use a diffusion filter with it.

Ultimately the 45/1.8 is an amazing little lens and is pretty universally beloved. To hell with sharpness charts. 🙄

I like the Olympus 45mm f1.8. It punches way beyond its size and cost.
P4010223 by matthewwatts3061, on Flickr

Lenstip don’t show this behaviour in their review, so maybe it’s an error.

Andrew

I've become focused on sharpness from looking at bird photos! However, I completely understand that a portrait can look better with some softness. The 'stop gap' prime would be more of a general lens, so around 20mm up to 45mm seemed about right and because it would be a general lens, I was looking for the best overall quality in these less expensive primes.

I still haven't decided, but a used 45mm does seem a bargain at the moment with its good reviews.

"Tack smooth skin"???

But, yeah, I get it. Who want to count every pore? Yuck!

Which is why I have no problem doing corporate portraits with MFT and a decent zoom rather than my 42MP detail beast. I mean, odds are those images will never be seen bigger than 2048px online.