450mm lens with 420mm bellows draw?

[ic-racer]

Any ideas of how to make this work based on experience?

In this situation I have used an extension bellows. It addresses some of the issues mentioned above.

[Maris Rusis]

One desperate trick I've resorted to is to shorten the focal length of a lens. The 300mm I use on my 8x10 camera is sometimes too long and I want something slightly wider. Answer? Screw a #1 close-up lens on the front. A 450mm with a #1 close-up lens on it reduces to an effective 310mm. How to use? Focus a couple stops down from wide open to allow for most of the inevitable focus shift and then stop way down for the actual exposure. Result? Tolerable image quality compared to no picture at all.

I have and use top-hat lens boards occasionally on my Tachihara 4x5 camera. The anxiety then is the strain on the front standard of the camera caused by a big lens hanging out there with extended leverage. And front swings and tilts with a top-hat lens board involve much increased image shift and the danger of mechanical vignetting. Compromise, compromise.

[Bob Salomon]

One desperate trick I've resorted to is to shorten the focal length of a lens. The 300mm I use on my 8x10 camera is sometimes too long and I want something slightly wider. Answer? Screw a #1 close-up lens on the front. A 450mm with a #1 close-up lens on it reduces to an effective 310mm. How to use? Focus a couple stops down from wide open to allow for most of the inevitable focus shift and then stop way down for the actual exposure. Result? Tolerable image quality compared to no picture at all.

I have and use top-hat lens boards occasionally on my Tachihara 4x5 camera. The anxiety then is the strain on the front standard of the camera caused by a big lens hanging out there with extended leverage. And front swings and tilts with a top-hat lens board involve much increased image shift and the danger of mechanical vignetting. Compromise, compromise.

Have you ever checked out minus lenses? And with the cost of time and materials shooting large format why would you settle for tolerable/mediocre quality? Or don’t you care?

[Maris Rusis]

Have you ever checked out minus lenses? And with the cost of time and materials shooting large format why would you settle for tolerable/mediocre quality? Or don’t you care?

Yes, I've done extensive trial with minus lenses from -0.5D to -2.5D. The stronger the supplementary lens the worse is the image quality, as expected.

The reason to settle for tolerable image quality rather than no picture at all hinges on the other costs beyond materials. A memorable experience involved backpacking an 8x10 outfit several kilometres into extremely rugged country (Carnarvon Gorge, Queensland, Australia) to get to a scene (Moss Garden) that is fully visible from only one cliff top ledge. My lens, a 300mm, wasn't quite wide angle enough to take in this truly hard won scene so I added a +1 dioptre supplementary lens to deliver an effective focal length of about 230mm. Exposed at f64 the negative was good enough for a nice contact print. I don't possess the iron discipline to walk so far and hurt so much just to concede defeat in the interests of optical rectitude.