4x5 or 8x10 lens

[bwlf]

I plead ignorance about large format lenses.
One of the lenses I have... says "8x10". But it fits on my Wista 45N (4x5) no problem... Is there some inherent difference between 8x10 lenses and 4x5 lenses?

This is the same question I have been struggling with myself, and did not find it answered here in the forums or in the large format lens primer... so please excuse me resurrecting this old thread and I appreciate your help in trying to understand!

What I am concerned about is the "crop factor" of e.g. a 150mm lens with an image circle for 8x10 being used on a 4x5 back. Is this now essentially a 300mm lens focal length perspective on the 4x5 back/camera? (Similar to this unanswered photo.net question: 8x10 lens on 4x5 camera)

I have an 8x10 camera with 4x5 back, and plan to mostly shoot 4x5 but want my lenses to cover 8x10 as well. I just found the 8x10 lens list (which details the image circles ~320mm+) and the 4x5 lens list. Now my concern is that since the image circle of a 150mm lens for 8x10 (e.g. Nikon Nikkor SW 150mm f/8 -- has 400mm image circle) is nearly 2x larger than the 150mm lens for 4x5 (e.g. Nikon Nikkor W 150 f/5.6 -- has 210mm image circle)... I tend to believe there is also a 2x crop factor of the "8x10 lens" when used on a "4x5 camera" (same as swapping out the 8x10 back for a 4x5 back)?

So for 4x5 normal perspective (shooting 4x5 back on 8x10 camera), if I bought the 'wrong' 150mm lens (Nikkor SW instead for 8x10)... I presume I would effectively be shooting 300mm since I'm cropped in on the 150mm image circle for 8x10?

[Dan Fromm]

Come from digital, have you?

Crop factor. We don't even think in terms of crop factors. A 150 mm lens is a 150 mm lens is a 150 mm lens. Focal length is focal length is focal length.

That said, and no doubt having misunderstood your question completely, 150 mm is the normal (= the image's diagonal) focal length for 4x5. 300 mm is the normal focal length for 8x10. Set a 4x5 camera with a 150 mm lens next to an 8x10 camera with a 300 mm lens and the two will see the same field. Set the two cameras up each with a 150 that covers its format (or each with a 150 that covers 8x10) and the 4x5 will see a field whose diagonal is 53 degrees wide and the 8x10 will see 90 degrees.

If you want to use lenses that cover 8x10 on a 4x5 camera go ahead and do it. You'll pay a price in size and weight but its your back, not mine. I use lenses that cover 4x5, 8x10 and even larger formats on my little 2x3 cameras. Its no big thing and yes, my back doesn't like those big long lenses.

What was your question anyway?

[Oren Grad]

To cut to the chase: a 150mm Nikkor SW and a 150mm Nikkor W will give you the same field of view - the same picture - on a 4x5 sheet of film.

[John Kasaian]

If the 150 will cover 8x10 it should give lots of wiggle room on a 4x5. I think wiggle room is more important than crop factor, unless of course you're shooting agriculture.

[bwlf]

To cut to the chase: a 150mm Nikkor SW and a 150mm Nikkor W will give you the same field of view - the same picture - on a 4x5 sheet of film.

Thank you Oren... that sounds reassuring =)

Yes Dan, coming from digital and calculating crop factor... that's why I'm familiar with 150mm on 4x5 being equivalent to 300mm on 8x10 for "normal" perspective. Actually that seems to help as you said a 150mm lens on "4x5 will see a field whose diagonal is 53 degrees wide (normal) and the 8x10 will see 90 degrees (very wide)".... then both lenses see this wide angle of view... it's just cropped by the 4x5 lens back. I am assuming the lenses would both sit the same distance from the ground glass (be it 4x5 or 8x10 back) to be in focus at infinity.

So why does the image circle vary so much? Is this strictly a rear element function?

[bwlf]

150mm lens on "4x5 will see a field whose diagonal is 53 degrees wide (normal) and the 8x10 will see 90 degrees (very wide)".... then both lenses see this wide angle of view

So why does the image circle vary so much?

Ok, I think it just finally dawned on me... I was confusing "crop" with "zoom". So 'a 150mm lens is 150mm lens is 150mm lens' all provide the same zoom amplification in the lens - making the subject scene appear closer. These different 150mm lenses with their small and large image circles - is simply a more narrow or wider angle of view of that 'zoomed in' scene. While a 400mm image circle is projected, that does not mean the ground glass needs to cover that entire image circle... but it has that much "wiggle room" (rise, fall, tilt, shift) to essentially 'crop out' an angle of view for the size of film (e.g. 4x5 at 153.7mm, 5x7 at 208.6mm, or 8x at 312.5mm) which does become a wider view as the film/gg image area size increases.

[Corran]

To reiterate the term Oren mentioned - "Field of View" is the term you are looking for.

The Field of View is determined by the focal length and size of the film (or sensor) behind it. Whether or not the lens can fully illuminate the film (and/or how much you can utilize movements) of course depends on the lens.

I wouldn't use the word "zoom" when discussing a prime lens.

[Jerry Bodine]

It seems you're also confused about the term "perspective", which refers to the relative position of one object to another in the image. Perspective is synonymous with "point of view" and can only be changed by moving the camera/tripod to a different location. Therefore, if you were to keep the camera stationary the perspective of objects would remain unchanged with two lenses of different focal lengths (regardless of image circle). BUT if you then move the camera farther back so that the area included by the longer lens matched that of the shorter lens (at the previous location), you would see a change in perspective (point of view) but also an apparent flattening (compression) of the distance between near-objects and far-objects (known as "foreshortening"). Some refer to this foreshortening as "flattened perspective" which only adds to the confusion.

[Drew Wiley]

The 300L is a fairly heavy lens and shutter. So the main problem will be if your 4x5 front standard can support something like this without vibration.

[Liquid Artist]

While I was only shooting 4x5 I started intentionally adding lenses that would cover 8x10 with movements to my collection.
The reason being, I didn't want to buy lenses over again when I got a bigger camera.

This reasoning didn't exactly turn out as planned though.
I only upgraded to a 5x7, which most of my 4x5 lenses will already cover.
Plus my next camera will be 11x14 or bigger which only 1 lens I've already bought will cover.