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fralexis
29-Sep-2016, 07:18
I am looking at a fuji lens for my 4x5. The lens has an image circle of 213. Do you think that would be generally acceptable? I want to do some portraits as well as urban work. Thanks.

Alexis

AJ Edmondson
29-Sep-2016, 07:30
213mm will cover the 4x5 format and give you the ability to use some tilt and swing without being excessively limiting. You don't mention focal length which would be a consideration with portraits. Consider the distance you will be working at for your desired objective (head and shoulders, full-length, "environmental" portraiture).

Leigh
29-Sep-2016, 07:33
Hi Alexis,

The full diagonal of 4x5 is 163mm.

Your 213mm ic should cover that easily, but...

It depend entirely on how that ic is defined. Image circle is not a fixed value.

It will be smallest when the lens is focused at infinity and the aperture is fully open.
Focusing closer and/or closing the aperture will increase the ic.

Some lenses give the ic diameter when wide open.
Others give a value when stopped down (by two stops or to f/22 or ???), which will be larger.
You must review the lens' datasheet carefully.

Urban scenes are most sensitive to ic because you have fine detail throughout the field of view.

- Leigh

fralexis
29-Sep-2016, 07:35
Sorry. the focal length is 300mm. I anticipate casual portraits generally half length or perhaps a full length outdoor/environmental shot. Thanks.

fralexis
29-Sep-2016, 07:39
Hi Alexis,

The full diagonal of 4x5 is 163mm.

Your 213mm ic should cover that easily, but...

It depend entirely on how that ic is defined. Image circle is not a fixed value.

It will be smallest when the lens is focused at infinity and the aperture is fully open.
Focusing closer or closing the aperture will both increase the ic.

Some lenses give the ic diameter when wide open.
Others give a value when stopped down (by two stops or to f/22 or ???), which will be larger.

- Leigh

OK Leigh, so for example, if I were to have the subject about 5 feet away at an aperture of f8, that would have more of a image circle than a subject 15 feet away at an aperture of f 48?

Leigh
29-Sep-2016, 07:48
OK Leigh, so for example, if I were to have the subject about 5 feet away at an aperture of f8, that would have more of a image circle than a subject 15 feet away at an aperture of f 48?
Hi Alexis,

That's correct.

The image circle is a cone with its apex at the rear node of the lens.

The rear node is in front of the film by a distance equal to the lens focal length when focused at infinity.
In fact, that's the definition of lens focal length.

To focus on a closer subject you move the lens farther from the film.
Envisioning that cone, as the lens moves forward the diameter of the cone at the film plane increases.

- Leigh

Dan Fromm
29-Sep-2016, 08:56
Re coverage a near distances given coverage at infinity, see post #3 in this http://www.largeformatphotography.info/forum/showthread.php?67361-Calculating-lens-coverage discussion.

Leigh, isn't 4x5's image area's diagonal much closer to 150 mm than to 163?

Leigh
29-Sep-2016, 09:18
Leigh, isn't 4x5's image area's diagonal much closer to 150 mm than to 163?
Hi Dan,

The geometric diagonal of a 4" x 5" rectangle is 163mm.
The actual area on which light impinges when used in a regular film holder is likely closer to 150 than to 163.

As you approach the edge of coverage, light intensity drops gradually, not instantly.
I always use the larger number as a way to compensate for makers' fudge factors and "allowable" light falloff.

There's no way to tell what that fudge factor is/was.
And no way to tell how critical the corners are to a particular scene or shooter.

And as I stated earlier, the number is just a number supplied by the lens maker.
Its real value can vary both + and - for many reasons with any particular shot.

- Leigh

Alan Gales
29-Sep-2016, 09:43
Sorry. the focal length is 300mm. I anticipate casual portraits generally half length or perhaps a full length outdoor/environmental shot. Thanks.

You don't need a large image circle for portraiture.

Lachlan 717
29-Sep-2016, 14:03
Is it the Fujinon 300T?

Your stated IC seems quit small for a 300mm non-Tele.

If it is the 300T, it may not be the best lens for movements due to the position of the nodal point.

fralexis
29-Sep-2016, 15:17
Is it the Fujinon 300T?

Your stated IC seems quit small for a 300mm non-Tele.

If it is the 300T, it may not be the best lens for movements due to the position of the nodal point.

Yes it is that lens. Mainly I want it for portraits, although perhaps some urban or even landscape just to play around. For most urban or architecture I use a wider lens that has movement capabilities. Do you know the 300 T?

Alan Gales
30-Sep-2016, 14:10
I've never used a telephoto lens but they are nice for when you don't have the bellows length to use a regular designed lens of the same focal length. Telephotos are popular for portraiture with Speed/Crown Graphics and wooden field cameras. You should be happy with the Fuji for portraits.

Drew Wiley
30-Sep-2016, 15:57
If you have sufficient bellows length, it's generally preferable to use a non-telephoto design. For instance, a Fuji 300C will be optically much better corrected than
the telephoto version, with a much bigger usable image circle (often needed for sufficient rise in architectural subjects), be much more compact and therefore lightweight, and have the axis for swings and tilts near the center of the lens itself, instead of at some lopsided point. Otherwise, Fuji telephoto lenses have a good
reputation.