Flare testing a few lenses

[swmcl]

I've just sat down with a selection of lenses and pointed them towards the late afternoon sun. The sun wasn't on the groundglass but would've been nearly so.

When an assistant held a card to cover the lens from direct sunlight while I looked at the groundglass under the darkcloth I saw quite a difference between my lenses.

If there is a massive difference in the image flare can one assume the lens needs some attention?

I don't know if I've done something to seriously tell the difference between the men and the boys here but I can tell you that a renowned lens family had very little difference between shaded and unshaded whereas another brand and model was terrible in comparison.

I do think I'm talking about lens flare and not bellows flare here although when the sun was not in the image but was resolved onto the bellows I could definitely see it. I'm seeing a general 'fogging' right across the whole image.

Thoughts?

Get ready to send a lens to the manufacturer?

Cheers,

[Fredrick]

Is the lens in question multicoated?

[swmcl]

Yes. All the lenses are recent production. Rodenstock, Schneider and Fujinon.

[ic-racer]

Something like a coffee can that is painted black on the inside can be used. Place it in a daylight scene. Make it close enough so it makes a hole on the negative just a little bigger than the sensor spot on your densitometer. Expose the scene with each lens in question.

[swmcl]

I hear you about the coffee can but in this case, there were plenty of dark parts in the image and I can see an effect of the shading of the lens quite well in the groundglass on all the lenses. Unless I'm misunderstanding what's going on with a general fogging of the whole groundglass, which is a distinct possibility, I've got my money on lens flare. It helps to have an assistant turning the 'light' on and off for sure.

[Maris Rusis]

Take care with the sun disc just off the ground glass. With a large aperture lens the sun image focussed on the bellows will burn a hole clean through them in seconds. I was photographing some back lit flowers and wondered why the GG image was so indistinct. I found out when I took the back off the camera to change orientation and a big puff of smoke came out!

[swmcl]

Thanks Maris, much appreciated. As it was it was about 4:30 in the afternoon and yes, when I took the back off the camera and saw how bright the sun disk was I did think that things might get a bit smokey!!

I fully accept that I may have a magnifying glass of sorts doing this.

You Maris would know what lens I'm talking of. I'm not happy with the contrast of it and haven't been since its journey earlier in the year. I've contacted the Californian chapter of Schneider and am awaiting a reply. I'm thinking I've got some outgassing of a new cement.

Cheers,

[goamules]

I think flare can be caused by a few things. Lens design and number of air-glass surfaces, and the quality of the coatings would make a difference. But since all modern lenses are Planar designs, and you are shooting ones with modern coatings, differing flare is being caused by other factors. Different types of coating would make a difference.

Condition of the black paint inside the lens barrel, and internal features could case differences. The cleanliness of the glass can be a big factor too. If there are microscratches, haze or similar problems, there will be more flare when shooting into the sun.

Shooting into the sun is the most difficult situation for any lens, and if you find one that works for you well, just use that one.

[Kevin Crisp]

What were you trying to discover by testing?

[swmcl]

Thanks Kevin,

What bought the 'testing' on was a doubt about one of my lenses that had been recently serviced. Ever since it came back I've been looking through it and wondering about its performance. So the other day I came up with the idea of looking critically at a scene that included or nearly included the sun. I asked my son to shade and unshade my lenses and I just put a few of them in there to compare. What I got was a lens with a much poorer performance than the others and my query was to: a. determine whether my test was showing me anything relevant and, b. whether someone else had done something similar.

The lenses were Rodenstock Sironar S's 180mm and 240mm along with a Schneider 110mm Super Symmar and a Fujinon 300 C - all in tip-top condition. The Rodenstocks did show what I'll call flare but only very slightly, the Fuji was slightly worse and about 10 times worse was the 110mm Super Symmar. I've had the cementing issue sorted on the Symmar recently by Schneider in California and I'm happy that I can now focus the lens very well but I'm not sure of the contrast abilities. The 110 is absolutely clean as from the factory and is perfect to look at. There is certainly no obvious fogging of elements that I can see but it is a pretty small aperture on it for sure. If there is someone out there who has done this or could do this then I guess that would confirm or deny my observations I guess.

The 110mm has a very strong reputation but I don't know. I reckon the Sironar's are hard to beat.