CV wides: cornerfix, colorshift and vignetting

[uhoh7]

I'm sure for many here, this will not be new, but some may benifit from what I am learning now.

CV has a series of primes from 12mm to 35mm which are very small and optically excellent. They cost a fraction of normal leica glass.

They are designed for film, and when used digitally the produce colorshifts and vignetting. Till now this was only an issue for the chosen who possessed digital leicas.

But the everyman nex cameras have changed all that:

You can see the appeal.

Cornerfix is a free software program which was made to adjust these lenses post exposure in M9s. It works perfectly for the nex as well.

You create a lens profile by shooting against a white background---this is actually a bit tricky, and I just used snow, which is not ideal, but seems to work anyway.

Here are the results:

before:

CV 35mm f/2.5 color skopar

after:

the workflow goes:

download raw into folder, batch convert to dng, batch process with cornerfix, edit as needed in LR and export to jpeg.

this is my first effort. I think I would keep a touch of vignetting in my ultimate profiles: this is adjustable.

The point is it works.

 

[nigelb]

In general use I rarely use cornerfix to correct the images from the Skopar 35mm, vignette and colour shift not that noticeable, but I can certainly see the value of it with pale skies and snow. Cornerfix is pretty essential with the Helios 15mm, and often useful with the 25mm Snapshot Skopar.

Setting up a workflow for DNG converter and Cornerfix lens profiles is easy once you get the hang of it, but if you constantly change lenses it can get a bit confusing (wouldn't it be nice if the focal length appeared in the EXIF). It seems to discipline me to use fewer lens changes when I go out which isn't a bad thing.

 

[uhoh7]

In general use I rarely use cornerfix to correct the images from the Skopar 35mm, vignette and colour shift not that noticeable, but I can certainly see the value of it with pale skies and snow. Cornerfix is pretty essential with the Helios 15mm, and often useful with the 25mm Snapshot Skopar.

Setting up a workflow for DNG converter and Cornerfix lens profiles is easy once you get the hang of it, but if you constantly change lenses it can get a bit confusing (wouldn't it be nice if the focal length appeared in the EXIF). It seems to discipline me to use fewer lens changes when I go out which isn't a bad thing.

I'm still working on decent profiles for the 21 28 and 35. Not at all happy with the one above. Was hoping I could find some, but no luck, so I am playing with grey cards 🙁

 

[artur5]

Corner fix is for sure a great piece of software. That said, I'm not keen on having to fix every single image coming from a lens, not even with a semi automated batched process. For one thing, there's no Exif telling you which lens was used on which picture, so you have to know-remember-write down somewhere the information. Also, apart of wasting time in the process, the fixed image is not, by any means, like a picture coming from a retrofocus-telecentric design of a SLR wideangle.
To correct the cyan corners/vigneting, you must raise proportionally the level of red color and overall luminance, so you're increasing the visible noise, specially the red channel, and reducing the dynamic range on the outward parts of the image. There's no free lunch.

This is one of my reasons to keep away from rangefinder wideangles for using on my NEX. Another reason is the cost. A Zeiss Distagon 28/2,8 in Y/Contax mount comes at 1/3 of the price of a Zeiss Biogon ZM 28/2,8. Likewise, a Leica Summicron R 35 is way cheaper than the equivalent 35 in M mount.
Third: for some rangefinder lenses the minimal focusing distance is ( in my opinion) another negative factor. I just discarded the otherwise excellent C/V Ultron 35/1.7 because of the 0,9mtr/3 feet minimal focusing distance. Most 28mm SLR lenses go down to 0.3 mtr.
Of course, this is not an issue for everybody and some lenses, like the second version of the C/V Nokton 35/1.2, have a more reasonable m.f.d of 0,5 mtr. but then, this is a bulky, heavy and not that cheap lens..
Of course rangefinder lenses have big pluses too: small, light weight, well built and almost all of them very good performers. It's a matter of priorities. Provided the optical quality is good enough, I don't mind more bulk, weight and maybe distortion if I can get a decent price, no nasty color shifts at the corners and a convenient minimal focus distance.
I'm not bashing rangefinders, they're great but, for the time being, I'm sticking to reflex optics for my NEX.

 

[uhoh7]

Corner fix is for sure a great piece of software. That said, I'm not keen on having to fix every single image coming from a lens, not even with a semi automated batched process. For one thing, there's no Exif telling you which lens was used on which picture, so you have to know-remember-write down somewhere the information. Also, apart of wasting time in the process, the fixed image is not, by any means, like a picture coming from a retrofocus-telecentric design of a SLR wideangle.
To correct the cyan corners/vigneting, you must raise proportionally the level of red color and overall luminance, so you're increasing the visible noise, specially the red channel, and reducing the dynamic range on the outward parts of the image. There's no free lunch.

This is one of my reasons to keep away from rangefinder wideangles for using on my NEX. Another reason is the cost. A Zeiss Distagon 28/2,8 in Y/Contax mount comes at 1/3 of the price of a Zeiss Biogon ZM 28/2,8. Likewise, a Leica Summicron R 35 is way cheaper than the equivalent 35 in M mount.
Third: for some rangefinder lenses the minimal focusing distance is ( in my opinion) another negative factor. I just discarded the otherwise excellent C/V Ultron 35/1.7 because of the 0,9mtr/3 feet minimal focusing distance. Most 28mm SLR lenses go down to 0.3 mtr.
Of course, this is not an issue for everybody and some lenses, like the second version of the C/V Nokton 35/1.2, have a more reasonable m.f.d of 0,5 mtr. but then, this is a bulky, heavy and not that cheap lens..
Of course rangefinder lenses have big pluses too: small, light weight, well built and almost all of them very good performers. It's a matter of priorities. Provided the optical quality is good enough, I don't mind more bulk, weight and maybe distortion if I can get a decent price, no nasty color shifts at the corners and a convenient minimal focus distance.
I'm not bashing rangefinders, they're great but, for the time being, I'm sticking to reflex optics for my NEX.

Ty for interesting post

1) I am only learning CF now, so I am not an expert. But I have seen many images adjusted by CF from CV wides, with no evidence of increased noise whatever. Not to say that at pixel peeping levels it does not exist.

2) The extra step in the workflow is the price of extremely compact affordable wide CV primes. I have a number of superb SLR primes which do not require any fixes. They are large and heavy compared to the CV wides. When that's not an issue I use them.

you can see the following flickr for reference to CF end results:

http://www.flickr.com/photos/jhapeman/sets/72157624028500566/with/4142808692/

 

[rxmd]

2) The extra step in the workflow is the price of extremely compact affordable wide CV primes.

But the need for using adapted wide primes in the first place is only a result of Sony's extremely limited native lens lineup.

There are basically two classes of people who buy EVIL cameras. One buy them because they already have some lenses they'd like to adapt - these are typically the sort of people who don't mind fiddling with Cornerfix and keeping notes of what lens they used when because there is no EXIF data. (This group of people is also vocal on sites such as this and Flickr, but quite small.) The other group is those who want to use it with their native lenses. The Sony lineup doesn't really offer much flexibility for the latter group. Basically you have to use hacks like adapting rangefinder wides or use adapted A-mount lenses (which are then big, and some, such as the 11-18/f4.5-5.6, not all that great) because the platform doesn't offer anything else.

On 4/3 the situation is different. You can use lenses like the Olympus 7-14/f4 that are quite excellent and (by virtue of optimizing a lens for the sensor size behind it) both compact and cheap for what they offer - for $1500 new you get a useful range of focal lengths at very good quality that fully integrates into the system, whereas in the CV world a new 12mm lens alone will set you back $850 at least, isn't really all that wide in comparison, and forces you to do things like use Cornerfix, manual focusing and paper-based surrogate-EXIF notes. So if you want to do wideangles, 4/3 allows you to buy into a system, whereas the NEX at present forces you to resort to hacks. I guess Sony will do something about their lens lineup at some point in the future.

 

[uhoh7]

But the need for using adapted wide primes in the first place is only a result of Sony's extremely limited native lens lineup.

There are basically two classes of people who buy EVIL cameras. One buy them because they already have some lenses they'd like to adapt - these are typically the sort of people who don't mind fiddling with Cornerfix and keeping notes of what lens they used when because there is no EXIF data. (This group of people is also vocal on sites such as this and Flickr, but quite small.) The other group is those who want to use it with their native lenses. The Sony lineup doesn't really offer much flexibility for the latter group. Basically you have to use hacks like adapting rangefinder wides or use adapted A-mount lenses (which are then big, and some, such as the 11-18/f4.5-5.6, not all that great) because the platform doesn't offer anything else.

On 4/3 the situation is different. You can use lenses like the Olympus 7-14/f4 that are quite excellent and (by virtue of optimizing a lens for the sensor size behind it) both compact and cheap for what they offer - for $1500 new you get a useful range of focal lengths at very good quality that fully integrates into the system, whereas in the CV world a new 12mm lens alone will set you back $850 at least, isn't really all that wide in comparison, and forces you to do things like use Cornerfix, manual focusing and paper-based surrogate-EXIF notes. So if you want to do wideangles, 4/3 allows you to buy into a system, whereas the NEX at present forces you to resort to hacks. I guess Sony will do something about their lens lineup at some point in the future.

Not doubt 4/3 native lenses with AF are plentiful. Within one year we will see many more options for the nex from a number of lens makers.

How many of these will be as small and as sharp as a CV 28mm f/3.5 is open to question.

By your definition adjusting the white balance or noise of a raw file in LR could be considered a hack.

Everyone has their own priorites: for you obviously the 4/3 meets your needs much better than the Nex system. I my case, I'm interested in legacy glass of all descriptions and an RF-like experience. For that the Nex has no peer at the moment. The 2x crop of the 4/3 is brutal.

You mention the cost of CV lenses. However the fact is the used prices are much lower and extremely stable. They are very liquid commodities. If you pay a decent price you can't really loose anything.

And it's alot of fun to use them.

 

[ampguy]

same here

same here

no need for cornerfix on M8, film, or NEX with CV 15, 21, any 28 or 35.

I think it's a requirement for photoshop users only.

In general use I rarely use cornerfix to correct the images from the Skopar 35mm, vignette and colour shift not that noticeable, but I can certainly see the value of it with pale skies and snow. Cornerfix is pretty essential with the Helios 15mm, and often useful with the 25mm Snapshot Skopar.

Setting up a workflow for DNG converter and Cornerfix lens profiles is easy once you get the hang of it, but if you constantly change lenses it can get a bit confusing (wouldn't it be nice if the focal length appeared in the EXIF). It seems to discipline me to use fewer lens changes when I go out which isn't a bad thing.

 

[nigelb]

no need for cornerfix on M8, film, or NEX with CV 15, 21, any 28 or 35.

I think it's a requirement for photoshop users only.

??? I don't follow, please explain 😕

 

[uhoh7]

no need for cornerfix on M8, film, or NEX with CV 15, 21, any 28 or 35.

I think it's a requirement for photoshop users only.

What does photoshop have to do with it?

How many of these lenses do you own?

 

[Doug]

The genius of CornerFix is that the correction profile is made with your own lens, so the correction is neutral and as good as the profile. By contrast, the M8 & M9 use a lookup table to correct the same issues with a known lens type, and like CornerFix, the correction is applied in the RAW file. But it's approximate, even affected by the brand of the filter you use. If you apply a Leica code to a lens not in the coding chart, it's a further approximation, and CornerFix is likely to do a better job... though certainly with less convenience. Marvelous little program!

 

[uhoh7]

The genius of CornerFix is that the correction profile is made with your own lens, so the correction is neutral and as good as the profile. By contrast, the M8 & M9 use a lookup table to correct the same issues with a known lens type, and like CornerFix, the correction is applied in the RAW file. But it's approximate, even affected by the brand of the filter you use. If you apply a Leica code to a lens not in the coding chart, it's a further approximation, and CornerFix is likely to do a better job... though certainly with less convenience. Marvelous little program!

TY very much for reply Doug

getting a good profile shot is what many of us struggle with at first: any tips on that?

 

[gekopaca]

I've got a R-D1 and my favorite lens is Ultra-wide Heliar 12mm (LTM version).
Never had issues with corners or colors or something else.

Maybe the issue is the NEX sensor?

 

[rxmd]

I my case, I'm interested in legacy glass of all descriptions and an RF-like experience. For that the Nex has no peer at the moment. The 2x crop of the 4/3 is brutal.

To be honest I fail to see the "RF-like experience" in a camera that has no viewfinder and that makes you focus by zooming around on an LCD screen.

I find the market can currently be subsumed as follows:
(A) Digital camera
(B) Interchangeable lenses
(C) Rangefinder experience
...and you get to pick any two, or spend serious money.

getting a good profile shot is what many of us struggle with at first: any tips on that?

As usual, get a large enough grey card and take care of even illumination (outside under an overcast sky, for example).

Substituting the grey card with other more or less grey surfaces is inviting trouble IMHO, you end up importing whatever inaccuracies you had in reference test shot into every other picture you take.

 

[uhoh7]

To be honest I fail to see the "RF-like experience" in a camera that has no viewfinder and that makes you focus by zooming around on an LCD screen.

I find there are two kinds of people who know all about one camera or another and offer advice and judgement about them.

1) those that have one and use it.

2) those that don't.

Please excuse my use of "RF-like experience", which aparently offends you.

I will have to think of another way to describe shooting with RF lenses on a M8 sized crop with a very small form factor camera. I am open to suggestions.

If the main attribute of rangefinders is the focusing mechanisim, to the exclusion of optics, resolution and form factor, then I should not use the term.

As far as "zooming around the screen" being mandatory for focusing: far from it. The LCD is extremely sharp. "zooming" is optional, as is "moving around".

this is not to even mention many RF users prefocus for candid shooting. Is it still a rangefinder then?

nothing remotely "RF-like" there. What was I thinking?

 

[Doug]

Well, uhoh, the category boundaries are fuzzy, such that some cameras having no RF are still grouped with their related RF kin, such as Bessa L and Leica M1.

But I take rxmd's point, and RFF does have a name for the category that includes the NEX; the name of the forum in which this discussion thread resides. "CEVIL : Compact Electronic Viewfinder Interchangeable Lens".

 

[rxmd]

I find there are two kinds of people who know all about one camera or another and offer advice and judgement about them.

1) those that have one and use it.
2) those that don't.

3) And those that don't and have an informed opinion why. Do we agree on that?

Incidentally, appearances notwithstanding I'm not offended, and you shouldn't be either.

For me the key to the "RF-like experience" is the optical viewfinder with framelines in it. It's what gives immediacy to shooting. A camera that makes me frame and focus by chimping does not give me the same kind of feeling, no matter how small it is. The NEX's screen is OK but it's chimping nonetheless, and I find that for precise focusing I do need to zoom in, resulting in even less immediacy. I'm ready to do that on a ground glass with a 4x5, but with candids with a compact it feels extremely out of place for me.

Have you tried an M8 for an extended amount of time? Try it one day. The viewfinder is good, and the difference between 1,3 and 1,6x crop is the same as between a 20 and 24mm field of view when you put a 15 on your camera - it sounds small but it's quite signficant in practice.

 

[uhoh7]

hehe, chimping? is that squinting?

You guys are the experts on RFs, not me, and I have nothing but admiration for those who use them.

To many of us, and the camera buying public at large, the focusing mechanism has always been the least attractive thing about them.

Why did the SLR take over?

What is the attraction of an M9? It's small, unobtrusive and shoots full frame. Frameline focusing is something, it seems to me, that many buy the M9 in spite of, not because of--like the price.

Then there is the whole viewfinder thing--they don't have framelines at all.

The nex crop is 1.5, not 1.6, but I had not realised the M8 was 1.33, which is obviously much better.

The nex is not a rangefinder, of that there is no doubt. But in terms of field application--it's size and the glass it uses, it's as close as you get without the framelines. So for me, it's "RF like". It's been called the poor man's M9, so I'm not the only one who feels that way.

I yearn for the day I can throw out my nex and use a full frame short register EVIL with the glass I love. I do not however yearn for framelines. This may only be ignorance on my part. When I have the chance I will play with them.

I do thank you both for your input and insight.

Now, back to shooting a decent profile for the CVs.

How big a grey card do you think is needed?

I printed out one on a letter, but I am not liking the results.

Grey is better than white poster board?

best,

 

[rxmd]

hehe, chimping? is that squinting?

Chimping is when people look at the back of their camera, either during or after taking a shot:

Again, what I like about RF viewfinders is not primarily framelines - incidentally, those aren't used for focusing, they are used for framing. What I like about them is the immediacy of being right in the action. I get less of that in an SLR viewfinder, still less on a ground glass, and still less on any electronic viewfinder I've looked at (or through) so far.

Now, back to shooting a decent profile for the CVs.

How big a grey card do you think is needed?

I printed out one on a letter, but I am not liking the results.

Grey is better than white poster board?

Well obviously it has to be large enough to fit in the frame with you at a comfortable distance, so that it gets evenly illuminated and you don't cast a shadow on it.

A grey card is a piece of cardboard (or cloth) with a defined 18% grey level. It's one of the things that many photographers tend to end up buying sooner or later. It's suboptimal to print one yourself because you don't know the base grey level of the paper you're printing it on, because you don't know the blackness level of the ink you're printing it with, and because your printer might print it a little unevenly and you end up importing these impurities into all pictures that you later correct with your printed reference image.

A grey card has a number of advantages over a white card. The most obvious one is that you can use it for other purposes, such as exposure measurements and (within limits) colour correction. Another advantage in your context is that you can crank up the exposure until just before you get blown-out highlights in the histogram. With a white card you are almost guaranteed to get blown-out highlights, and this may lead to inaccuracies in determining the vignetting, because Cornerfix has no way of determining where blowout ends and vignetting begins.

 

[ampguy]

Hi

Hi

I own all of the lenses I test with. No renting or borrowing.

The reason I mention photoshop is because out of camera, my Nex (and hundreds of others I evaluated images from prior to buying) did not have issues with 21 and up like your images do, with your photoshop use.

I do have slightly visible corner issues with the CV 15, but again, not to your extent. And never the issues you've shown with your CV 21.

So, assuming your NEX is working fine, and your lens sample is good. Then why not try posting some non 'shopped photos, and still see if they need some 3rd party corner fixing.

What does photoshop have to do with it?

How many of these lenses do you own?