How much is IC affected when moving up in Format Size?

[audioexcels]

Theoretical numbers will be used here.

In terms of movement potential, lets say we have 75mm lens on 4X5 film that has 60mm's more IC than is required for the format (bare minimum to cover the sheet). We have a 150mm lens on 8X10 that has similarly 60mm's more IC than is needed to cover the sheet.

What are more realistic numbers when it comes to translating the amount of IC one can expect to have useable to them on the 8X10 sheet vs. what is available on the smaller 4X5 sheet...

OR

Is IC plainly just IC, and the amount of IC required for doing whatever movements one wants to use in order to use up those 60mm's of IC does not apply regardless of size of film?

[Ole Tjugen]

I don't quite understand the question here...

IC is just IC, and the Image Circle is a circle. The film is a rectangle. How much movements are available in each direction depends on image circle, film size, and film shape. 4x5" and 8x10" have the same aspect ratio, which makes it a little bit easier to calculate.

[audioexcels]

I don't quite understand the question here...

IC is just IC, and the Image Circle is a circle. The film is a rectangle. How much movements are available in each direction depends on image circle, film size, and film shape. 4x5" and 8x10" have the same aspect ratio, which makes it a little bit easier to calculate.

So we take a 4X5 and 8X10 into the field. We are composing the identical photo. We use a 75mm lens and the photo we are taking requires 40mm's of IC...We are using a 150mm lens on the 8X10. Will the 8X10 require more IC to get the same image as the one taken on 4X5?

Sorry if this doesn't make sense. Will try to elaborate more if it doesn't.

[tim810]

The image circle of a lens is that, a circle. The diameter is fixed and can't be changed.
For instructional purposes we will use your 75mm with a IC of 6.4 inches and second 75mm with a IC of 12.8. We label these lenses A & B respectively. ( Calculating the usable IC of a particular lens is difficult and is also usually published by manufacturer or someone with experience with the lens. )

Now draw a perfect circle around a 4x5 piece of film and also a 8x10 piece of film. Also draw a line from one corner of the film to the next. This is the diagonal of the film or required diameter of the Image circle necessary to cover the film. If the diameter of the circle of the lens is smaller than that of the diagonal line of the film it doesn't cover as well or at all (some lenses cover better than advertised).

The formula for calculating the diagonal of a piece of film be it 5x8 or 12x20 is to take

the spuare root of [(x^2)+(y^2)]

if you go through this calculation you will find that 4x5 has a 6.4 inch diagonal and 8x10 has a 12.8 inch diagonal.

Example: if you use lens A on 8x10 film than you will get a circular image in the center of a 8x10 piece of film with a diameter of about 6.4 inches. But, if you use lens's A and B on the 4x5 and 8x10 respectively than you will cover your format. barely.

If you want the same angle of view for a given subject using a 4x5 and an 8x10 you need a 75mm (6.4 inch IC) lens on the 4x5 and a 150mm (12.8 inch IC) lens on the 8x10. Both lenses also need to have the same angle of view. Which with these IC's at infinity should have similar angles of view.

Lastly these calculations are if you use this lens at infinity where the axes of the lens is 75mm away from the film plane. If your closer to the subject than the lens is farther away from the film plane and is omitting a larger IC than if at infinity. At 2x infinity or the distance from axes to film plane is 150mm than the image circle is also increased by 2x. So usable IC is now 12.8 inches. the only problem is that now the image density is now 1/2 as bright (maby not by that much but it will take longer to expose usually(personally I double exposure and add reciprocity with the film I use)).

Example: your doing a close up with your 8x10 using lens A (yes the smaller IC lens). The distance from axes to film plane is 150mm now the IC of lens A is 12.8 inches and covers the 8x10 diagonal.


I hope this helps I have more calculations but figured I would "try" and keep it simple.

[Walter Calahan]

Eye See.

You are making your life way to difficult.

As long as you can move the rectangle within the circle you are fine. If the rectangle moves outside the circle you still may be fine if you like the look (Grin).

The angle of view of a 4x5 lens and an 8x10 lens has to match if you want the same 'look' on both formats.

More importantly than all these angels on the head of a needle is GO OUT TO MAKE PICTURES.

[Ron Marshall]

The front page of this site has spreadsheets with the movements possible on modern lenses on the different formats.

If you have Excel it is simple to construct such a table for yourself:

http://www.largeformatphotography.info/lenses/

[Bob Salomon]

Image circle changes with image ratio and aperture. Not with the size of the film.

So a Rodenstock 75mm 4.5 at infinity at f22 has an image circle of 195mm. With 6x7cm film you would have 63mm of rise and 59mm of shift in landscape (horizontal). With 6x9cm film you would have 59mm of rise and 49mm of shift, with 4x5" you would have 29mm of rise and 25mm of shift. At all times you had the same 195mm of image circle at f22 at infinity. The only change was the film size. You would not have enough IC to cover 57 or larger at f22 at infinity with this lens.

[Patrik Roseen]

I think the question is not related to the IC, more towards the movements necessary for the same type of composition on 4x5 and 8x10.

If one uses a normal lens on 4x5 and needs 20mm of rise, what would be the required level of rise for a normal lens on 8x10? Would it still be 20mm or more?

(audioexcels, is this what you mean?)

[audioexcels]

I think the question is not related to the IC, more towards the movements necessary for the same type of composition on 4x5 and 8x10.

If one uses a normal lens on 4x5 and needs 20mm of rise, what would be the required level of rise for a normal lens on 8x10? Would it still be 20mm or more?

(audioexcels, is this what you mean?)

Yes, precisely. Say we are using even 40mm's of rise on both the 4X5 and 8X10 format, using a wide, normal, etc. Will both still only need 40mm's or will one need more than the 40mm's...

[Kevin Crisp]

http://www.largeformatphotography.info/lenses/LF4x5in.html

This is for 4X5, others are on this site as listed on the home page. A very helpful resource.

[audioexcels]

4X5:

Schneider Super-Angulon XL 72 f/5.6 f/45 226

Excess Coverage=72.3
Excess%=31.99



8X10:

Nikon Nikkor SW 150 f/8 f/64 400

Excess Coverage=87.5
Excess%=21.88


A 72mm lens on 4X5 sheet film with less IC than the 150mm lens on 8X10 film gives 50% more excess coverage%...


What puzzles me is that users of the Nikkor 150SW have felt no need for a center filter (color or b/w) since it has plenty of coverage and provides excellent movements.

Why is this the case when the majority of 75mm F4.5-F5.6 lenses that have a similar or greater percentage of coverage than the Nikkor 150SW on 810 sheet film need a center filter? Rather, that most would say anything below a 90 on 45 sheet will need a CF especially shooting color film.

[Ron Marshall]

4X5:

Schneider Super-Angulon XL 72 f/5.6 f/45 226

Excess Coverage=72.3
Excess%=31.99



8X10:

Nikon Nikkor SW 150 f/8 f/64 400

Excess Coverage=87.5
Excess%=21.88


A 72mm lens on 4X5 sheet film with less IC than the 150mm lens on 8X10 film gives 50% more excess coverage%...


What puzzles me is that users of the Nikkor 150SW have felt no need for a center filter (color or b/w) since it has plenty of coverage and provides excellent movements.

Why is this the case when the majority of 75mm F4.5-F5.6 lenses that have a similar or greater percentage of coverage than the Nikkor 150SW on 810 sheet film need a center filter? Rather, that most would say anything below a 90 on 45 sheet will need a CF especially shooting color film.

My 75mm has an image circle of 195mm, so I can't make large movements. If I am shooting neg with the 75mm I often don't bother with a CF. But with the 72mm and large movements I would use a CF. But, it's obviously a personal decision as to how much falloff is acceptable.

[Bob Salomon]

4X5:What puzzles me is that users of the Nikkor 150SW have felt no need for a center filter (color or b/w) since it has plenty of coverage and provides excellent movements.

Why is this the case when the majority of 75mm F4.5-F5.6 lenses that have a similar or greater percentage of coverage than the Nikkor 150SW on 810 sheet film need a center filter? Rather, that most would say anything below a 90 on 45 sheet will need a CF especially shooting color film.

Because the SW series needs a center filter just as much as Schneider, Rodenstock and Fuji do. If one does not see the need for it on the Nikon they won't on the others as well.

One of the main reasons was that Nikon never offered a CF in their program so many people assumed that one was not needed. Not so.

The need for the filter will depend on what you shoot, how you shoot and what you want to do with what you shoot just as much as the lens itself.

[audioexcels]

I have read numerous threads from users of both Nikkor 150SW and Schneider Symmar 150XL lenses, and the 150XL absolutely needed a CF when the Nikkor did not. In other words, the same shot required a CF with the Schneider but not with the Nikkor. The Schneider CF will fit the Nikkor and Heliopan possibly marketed one for it also.

[Ron Marshall]

I have read numerous threads from users of both Nikkor 150SW and Schneider Symmar 150XL lenses, and the 150XL absolutely needed a CF when the Nikkor did not. In other words, the same shot required a CF with the Schneider but not with the Nikkor. The Schneider CF will fit the Nikkor and Heliopan possibly marketed one for it also.

They may or may not be required!

On 4x5, using neg film and without large movements neither requires a CF. On 8x10 with large movements and positive film most people would probably use a CF.

[Really Big Cameras]

Yes, precisely. Say we are using even 40mm's of rise on both the 4X5 and 8X10 format, using a wide, normal, etc. Will both still only need 40mm's or will one need more than the 40mm's...

No, if we assume film dimensions that are twice as big and the focal length of the lens is twice as long, you'll need twice as much rise to get a comparable composition on the larger format. It's all just a function of simple linear proportions.

For simplicity sake, lets assume a 4x5 image is exactly 4" x 5" and an 8x10 image is actually 8" x 10" (they aren't in real life due to nominal film sizes and film holder margins, but they're close enough for a simple approximation). So, the 8x10 image is exactly twice as tall and twice as wide as the 4x5 image. Now, let's take a 75mm lens with a 200mm image circle on the 4x5 format and a 150mm lens with a 400mm image circle on 8x10. Again, everything scales by 2x - both focal length and image circle. Now, if you apply 20mm of front rise using the 75mm on 4x5, you'll need to apply exactly twice as much front rise (40mm) when using the 150mm lens on 8x10 to get the same composition.

Another way to look at it is that the 75mm lens with a 200mm image circle gives you approximately 30mm of usable front rise (in landscape orientation) on 4x5 and the 150mm on 8x10 gives you twice as much excess coverage - approximately 60mm. However, you need twice as much rise to get the same affect.

Kerry Thalmann
Really Big Cameras (http://reallybigcameras.com/)

[Really Big Cameras]

I have read numerous threads from users of both Nikkor 150SW and Schneider Symmar 150XL lenses, and the 150XL absolutely needed a CF when the Nikkor did not. In other words, the same shot required a CF with the Schneider but not with the Nikkor.

The lenses are different designs, therefore, their illumination fall-off characteristics are different. Modern wide angle lenses like the Nikkor SW, the Schneider Super Angulon, the Fujinon SW and the Rodenstock Grandagon employ a tilting entrance pupil to reduce illumination fall-off compared to lenses of standard design. The Super Symmar XL series do not employ tilting entrance pupils and therefore have greater illumination fall-off than other recent wide angle designs that do.

The theoretical best-case illumination fall-off for lenses with a tilting entrance pupil follows the function cosθ^3 (cosine theta to the 3rd power). Theoretical illumination fall-off for lenses without a tilting entrance pupil follows the function cosθ^4 (cosine theta to the 4th power). If you look at the illumination charts for modern lenses you will see that they come very close to achieving these theoretical best-case illumination characteristics.

So, if we assume an image diagonal of 312mm (which is an actual measurement on one of my 8x10 negatives) for 8x10, a lens like the 150mm Nikkor SW with a tilting entrance pupil will have an illumination fall-off of approximately 1.59 from the center to the far corners of the film (assuming the lens is centered). For a 150mm lens without a tilting entrance pupil, like the 150mm Super Symmar X, the fall-off in the far corners increase to 2.12 stops. Both lenses have fall-off, but the 150mm SS XL has more and that would explain why some users would claim it needs a center filter on 8x10, while users of the 150mm Nikkor SW swear no center filter is needed.

Whether or not a center filter is needed/desirable is ultimately a personal choice. It depends on the film you are using, your printing methods, and more than anything else, your personal sensitivity to illumination fall-off in your images.

Kerry Thalmann
Really Big Cameras (http://reallybigcameras.com/)

[audioexcels]

Thanks a lot Kerry. Very simply put and coherent. I appreciate it.