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.in...s/LF4x5in.html

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