Minolta DImage Scan dual F-2400 - scanner lens

[Beatsy]

Thanks Rik - that's easier than I thought. I measured 3 extensions to check the numbers and got a bit of variance, but I assume it's close enough (rounded all to 2 decimal places).

Pupil is 6.5mm (assuming that just means the diameter of the light disc seen through the lens held at arms length).

Ext1 = 20mm = 1.84x
Ext2 = 45mm = 2.56x
Ext3 = 100mm = 4.08x

There is additional extension from another adapter and the lens being up inside the objective casing it's held in but I assume this irrelevant.

Using Ext1 and Ext2 (45-20)/(2.56-1.84)=(FL)34.78 and 34.78/6.5=F5.35
Using Ext2 and Ext3 (100-45)/(4.08-2.56)=(FL)36.18 and 36.18/6.5=F5.57
Using Ext3 and Ext1 (100-20)/(4.08-1.84) = (FL)35.71 anf 35.71/6.5=F5.5

So I get about 35mm and f/5.5. Does it sound in the ballpark for these lenses?

[ChrisR]

There is additional extension from another adapter and the lens being up inside the objective casing it's held in but I assume this irrelevant.

Yes, if they were in place for all three. It's the differences which matter.
The aperture sounds about right, but can you correlate it theory: https://www.cambridgeincolour.com/tutor ... graphy.htm ?
For a 4.5µm pixel, it looks to be 'limiting'.

[rjlittlefield]

For a 4.5µm pixel, it looks to be 'limiting'.

For some definition of "limiting". But see also http://www.photomacrography.net/forum/v ... 164#101164, which demonstrates that an f/11 optical image contains bars about 1.78 times smaller than are captured by a sensor with 4.7 micron pixels.

Assuming f/5.5 and 1.2X, effective f/12, then per http://www.photomacrography.net/forum/v ... 831#124831, the cutoff frequency for green light, 550 nm, will be 0.15 cycles/micron, 6.655 microns per cycle, so clearly finer than the Nyquist sampling limit of 9.0 microns per cycle with 4.5 micron pixels, even assuming no further degradation after that.

The pictures shown at cambridgeincolour will correctly suggest that the Airy disk diameter for f/12 has diameter greater than 3 pixel widths. But that's measuring to the first zero, and obscures the fact that the peak of the Airy disk is narrow enough that useful information still fits in less than one pixel width.

--Rik

[ChrisR]

Sure, the CIC page itself refers to "partially overlapping" and indicates a less than hard cutoff. Starting to have an effect.
Steve, does your arsenal have something to compare it with?

[Beatsy]

Sure, the CIC page itself refers to "partially overlapping" and indicates a less than hard cutoff. Starting to have an effect.
Steve, does your arsenal have something to compare it with?

You mean to compare resolution with?

I'm pretty sure a 5x Mitty pushed down to 3.375x on a 135mm tube would win for resolution in the centre. But I know the corners get mushy on FF so to my mind, the F-2400 will win overall (it's equally sharp across the frame and into the corners above 1.3x or so - even though 3.3x is approaching, or at, the top of its useful extension range).

I suppose the closest proper 'comparator' I have is MP-E 65 set at the same mag and f/5.6. That covers full-frame pretty well. Or should I use the MP-E at it's sweet spot (f/4 on mine)? And what sort of comparison target - just the wafer shots again? I'm concentrating on a few other stacks at the mo...

...but. I just won an Ebay auction for the carriage mech from a Heidelberg Linoscan 1800 (apologies if anyone here was also bidding). It has two lenses in it. Not that cheap, but I if those lenses are any good I think the price will have been a steal. We'll see - nothing ventured, nothing gained. I seem to have contracted a minor scanner lens bug - but I think this purchase should see it cured Anyway, that should arrive early next week. I'll roll it all up into one test and include those lenses in the comparisons (when I get them).

Edit: the seller sent them special delivery so I'll have 'em in my grubby mitts tomorrow (but busy elsewhere most of the day ). Should have some results by the weekend.

[Lou Jost]

Good job! Our universe of lenses is expanding rapidly!

[Vector1968]

Thanks for sharing this.

[RobertOToole]

Good work on this one Beatsy.

Just got back in town from 2 weeks in Africa so I am a little late with my info. I actually have one of these, my lens was from the multi II and was encased in plastic housing and was way too much trouble to remove so I wouldn't recommend the lens to anyone but was this the case with your lens?

The diameter of the lens is so small I was not going to bother with the hassle of even mounting it so I actually offered the lens for free to the first taker, its spoken for now.

But the good news is that I just received a Minolta Multi Pro F-5000 medium format scanner so I will have the Multi-pro, Elite 5400 I and II, and the Multi-II lenses here. Maybe I can set-up a test over the next few days once I catch up here in the office.

Multi Pro specs:

http://www.konicaminoltasupport.com/fil ... s2887e.pdf

FYI, Minolta Scanner Specs:




Best,

Robert

[Beatsy]

Good work on this one Beatsy.

Just got back in town from 2 weeks in Africa so I am a little late with my info. I actually have one of these, my lens was from the multi II and was encased in plastic housing and was way too much trouble to remove so I wouldn't recommend the lens to anyone but was this the case with your lens?

Thanks Robert. Sorry for the delayed answer, I only just noticed your post.

I'm not sure if this is the plastic housing you mean but as you can see, I had no difficulty getting the lens out. The process was controlled but not at all gentle Once the lid was prised off, the lens was easily lifted out as it was only held in place by a couple of blobs of silicone-sealant type stuff.


The F-2400 lens really is a little cracker. Despite being distracted by a pair of lenses from the Heidelberg Linoscan 1800 (one OK, one fantastic - testing still underway and awaiting parts) I keep returning to the F-2400 for another "little play".

The sweet spot is extensions of 90mm to 150mm (from sensor to back of lens) which gives magnifications of 1.25x to 3.0x respectively. This covers full frame with a minimal little clip of vignetting and mush in the extreme corners at the lowest mag - and all clear by 1.35x. The range can be pushed further at both ends, but you get bigger mushy corners and more vignetting at the low end and begin to exceed the resolution at the top. It can be usefully pushed to 4x though (~190mm extension), and maybe beyond, but that's too unweildy on my rig, so I'm not bothering with it. I'm looking for a circa 2x solution anyway and this lens suits admirably. Only downside is the short-ish focal length of ~35mm which causes strong perspective distortion and results in loss of the edges to "streakies" in stacking. Depends how deep the stack is of course, deeper = more lost to streakies, but it does rob some of that extra FoV gained from lower mag.

[RobertOToole]

Hi Beatsy

That looks a heck of a lot easier to remove than my scanner.

I just figured it out, I had the F-2820 not the F-2400.

The 2820 has the lens encased in plastic. It took a chisel to remove it.

I wouldn't recommend it unless its really cheap, I think I paid $20, that was too much, the seller should have paid me for taking it off his hands

This is what it looks like.

[Beatsy]

Yeah, not that one Robert. This one...

https://www.ebay.co.uk/itm/Minolta-Dima ... 2759236365

Note: there's 26 days left on this Buy It Now (or Make Offer), but I suspect it won't be around much longer! I'd have bought it, but I already got mine

[RobertOToole]

Yeah, not that one Robert. This one...

https://www.ebay.co.uk/itm/Minolta-Dima ... 2759236365

Thanks.

I posted info on the F-2820 so people wont make the same mistake as I did and buy one.

This is your unit I believe:

http://www.konicaminoltasupport.com/Dim ... 659.0.html?

[Beatsy]

Yep, that's the one