5 x 7" negative coverage

[pkbench]

What are the exact dimensions of an image exposed on a 5 x 7" negative in a standard 5 x 7 film holder?

How much should the image circle of a lens exceed the diagonal of film so that vignetting is not noticeable?

 

[keithwms]

About 4 7/8" x 6 3/4".

The image circle must be at least larger than the diagonal- this is the bare minimal requirement to cover the neg with no movements. But you can (and do) have falloff with wide lenses, even if the image circle is sufficient....

 

[pkbench]

That is my question for the fast 90 mm lenses have image circles in the 235 mm range whereas the 105 and 115 lenses have image circles in the 250 range. I want a lens that will not cause noticable vignetting, primarily with black and white negatives. Thanks. CL

 

[Ole]

The diagonal is about 210mm. So an image circle of 210mm will cover - exactly, when perfectly zeroed and centered, with zero vignetting.

But there is a difference between "image circle" and "circle of illumination". One example is the old 120mm Angulon: The stated image circle at 211mm is just enough for 5x7" (205mm), and just falls at the 211mm needed for 13x18cm. Yet it is quite useable on 13x18cm even with a little movements, since the circle of illumination far exceeds the image circle, and a slightly softer bit in the outer mm in one or two corners will rarely be noticed.

 

[Dan Dozer]

Back when I shot 5 x 7, (regardless of what the Schneider posted image circle information is) I used both my 210 Symmar S F5.6 and 90mm Super Angulon F8 with no vignetting problems at all. However, with the 90mm, I did not get any rise/fall adjustements due to the short focal length.

 

[keithwms]

CL, there should be enough wiggle room for the 90 to hack it if you are careful and stop down liberally.

The image circles you found are probably for infinity focus at f/22. Something that might make the difference: how closely will you be focusing? When people do ultrawides, they often are not focusing at infinity but rather quite a bit closer, in which case the coverage will be larger than stated in the specs.

Anyway, worst case, you crop a tiny bit off the edges of the neg. You still wind up with a substantially wider shot than you'd get on 4x5

 

[pkbench]

So image circle is the lens coverage before light falloff occurs, therefore I will not need a center filter for my Rodenstock Grandagon-N 90 mm f 6.8 lens (image circle 221 mm) on a 5 x 7 camera. Thankk you for the information. I guess someone just wanted to sell me a center filter.

 

[pkbench]

Keith, I am trying to get the Fotoman 57PS, and I will probably use the hyperfocal distance at f22 most of the time.

 

[pkbench]

Ole, what is the diagonal of an exposed 5 x 7" negative, 205 or 210 mm?

 

[Ole]

So image circle is the lens coverage before light falloff occurs, therefore I will not need a center filter for my Rodenstock Grandagon-N 90 mm f 6.8 lens (image circle 221 mm) on a 5 x 7 camera. Thankk you for the information. I guess someone just wanted to sell me a center filter.

NONONONO!

The image circle is the lens coverage before the image sharpness decreases to below some level decided upon by the lens manufacturer, NOT the point at where light fall-off becomes noticeable!

I've posted (repeatedly) an image shot with a 90mm f:8 Super Angulon on 13x18cm film, where the light falloff is "camouflaged" in the dark valley sides. And (also repeatedly) a link to a page where I use a 90mm f:6.8 Angulon on 13x18cm film, showing both the extent of the image circle, the circle of illumination, and the degree of light falloff. The plain old Angulon shows no vignetting, but severe falloff. The newer 90/8 SA shows far less falloff, but vignettes sharply at the end of the image circle.

With some scenes you can easily get away with not using a center filter on a 90mm SA on 5x7" film. With other scenes it will be a huge improvement.

 

[Ole]

Ole, what is the diagonal of an exposed 5 x 7" negative, 205 or 210 mm?

205mm, according to Schneider. I use "about 210mm" since I use both 5x7" and 13x18cm film, frequently on the same day. 210-ish is close enough - see my prevoious post(s).

 

[Ole]

Dead Link Removed

There. That's my "Angulon shootout".

Remember that these shots were done partly to illustrate the difference between the three parameters: Image Circle, Illumination circle, and illumination falloff. So they show a lens which is said to barely cover 4x5" straight on with no movements at small apertures, used on a much larger film size.

Notice that the illumination falls off from the center out (the images get darker), yet there is some image all the way into the corners. But the sharp image ends a little bit in from the corners, showing that the circle of illumination is much larger than the image circle in this case.

A center filter will even out the illumination, giving more even exposure across the field. But the circle of illumination may actually get smaller, since the filter might vignette a little bit of the extremem ends of the circle of illumination. The image circle will be little if at all affected.

 

[pkbench]

Ole, how might I see thoise images? Thanks CL

 

[Ole]

Click the link, and click the thumbnails on the new page. Each image opens in a new window.

 

[pkbench]

Sorry, I just noticed the link.