Technical Imaging - Effect of bellows extension.

[Pete Askew]

Following some questions raised from the thread on the use of a bellows unit for macro photography I thought the following might help with the understanding of the relationship between bellows extension, distance from subject, magnification and exposure. This was shot using the same setup as described in http://www.realphotographersforum.c...o-photography-using-copy-stand.html#post38745, even the same flower! The only thing that was changed was the amount of extension behind the lens. To achieve focus, this mean also adjusting the lens to subject distance. The results show the effect on subject size in the frame and exposure as the same setting were used for each shot. Note the upper LH control patch (M in the shot with the lowest magnification): this is the nominal mid grey and is actually only 'correctly' exposed in the shot with the lowest magnification (as discussed in the previous post). I hope this makes some sense.

Same magnification etc as in http://www.realphotographersforum.c...o-photography-using-copy-stand.html#post38745 but with an exposure scale card included. This has a total of 275 mm extension giving a lens to subject distance of 145 mm (bellows at near maximum extension + 56 mm and 32 mm extension tubes).

A total of 250 mm extension giving a lens to subject distance of 160 mm (bellows at near maximum extension + 56 mm extension tube).

A total of 185 mm extension giving a lens to subject distance of 185 mm (bellows at near maximum extension).

A total of 125 mm extension giving a lens to subject distance of 300 mm.

A total of 80 mm extension giving a lens to subject distance of 500 mm.

The reason I never use maximum extension is to allow some movement for fine focus as this is easier than using the column or the rack (due to the weight of the camera).

Hasselblad ELM (mains-powered version) + Zeiss 135 mm f1:5.6 CF S-Planar or Hasselblad Auto-Bellows +/- 56 mm and 32 mm extension tubes shot onto a Phase One H20 at 50 ISO into Capture One Pro 6, 1s at f1:22. Exported via LR after 40% adaptive sharpening in Nik Output Sharpener.

 

[Brian Moore]

Is that a wee bit of dust I see on the petal on the right? (If so I LOVE that!)

Thanks for posting this Pete. I didn't see your first post on this subject for some reason but taking a look at these images and then going back to the first post is really enlightening as to the rig and the set-up. Pretty amazing to me, really. Unfortunately this kind of work is so far out of my league that I wouldn't even know what to say. (Other than ask about the dust, a subject about which I know much!)

 

[Pete Askew]

Thanks Brian. Actually it's on the sensor - it stays in the same place as the magnification changes. Time for a quick clean I think. Fortunately this is dead simple with a back as it easy to access and huge! More than can be said for the S/H D3x I just bought (broke my rule about buying SH digital - although it was OK with a second S5 Pro we bought the other day). The camera has only had 1800 actuations. Unfortunately all inside a flour mill with the lens off!! So, it'll either be a pro-clean by the dealer or it will go back and I'll buy a new one instead!

 

[Hamish Gill]

Ive cleaned a few sensors in my time Pete, more than happy to give it a go for you ... ?
I think I owe you a favour or 2

thanks for posting this, does certainly help demonstrate what we were talking about before!

 

[Pete Askew]

Thanks for the offer Hamish. It was supposed to have been in mint condition and will be cleaned professionally by Nikon through the dealer. In that way, if any of the marks don't come off he can give me a refund and order a new one from Nikon for me.

Part 3 on its way!! So much for working today - I'm also making up some ID11 but just remembered about the heater and now have to wait for the water to cool back to 40°C from 70°C!!