Loupe for checking Velvia?

S

ssmc

Well-known
Local time
2:56 AM
Joined
Feb 2, 2009
Messages
596
I got some strange-looking scans of 35mm Velvia 50 and I'd like to check the film itself for sharpness. Basically I need to see whether the problem occurred in the camera (two different bodies and lenses shot at the same time) or if it's the scans. Obviously I don't have a scanner myself at the moment!

The reason I ask specifically is that there seems to be a wide range of magnifications available and I know that Velvia is extremely fine-grained.

Sorry for the "noobishness" of the question!
Scott
 
To check fine detail I would use the strongest magnifier you can see through comfortably. I have 9x and 12x loupes from edmund scientific. They are not difficult to use. I also have a variable power one called the "Emoscope," which can be used at a whole bunch of powers, from 3x up to 35x. It is a little fussy to use, but if you need to inspect near the limits of resolution for Velvia, or for a scanner, you might need the magnification of the Emoscope. I found mine online some years ago. At 35x, it is approaching low-power microscope magnification!
 
I used a 4x Schnieder loupe for judging the sharpness of 35mm Velvia during the twenty years I shot slide film. Low power maybe, but I looked at so much film I could quickly spot the soft ones to discard. The image quality is great on that loupe.
 
Most loupes will outresolve flatbed scanners. If you want to judge critical focus, you'll need a 10x loupe. For viewing the entire frame, 4x to 5x. It's somewhat academic as all the good loupes (Schneider, Rodenstock, Contax, Cabin/Mamiya) are discontinued and you'll have to scour eBay. Most Peak loupes are garbage. One decent option are the Belomo triplet loupes meant for mineralogists. Not as convenient as proper photographic loupes, but inexpensive and still available.

For more details:
https://majid.info/blog/going-all-loopy-about-loupes/
 
Do you find that slide film is more difficult to scan than C-41 or B&W? I do; maybe it is the layers of dye that are present, or something else. I have a couple of thousand slide and when I scan I'm always feeling compromised. Maybe some RFF member can answer both of our concerns and maybe it is the same answer.

Here is one that I took in 1963 (Ektachrome), but with very careful adjustment of the height off the glass it is one of my better attempts. I use a V500:

1963 by carter3john, on Flickr


And this is a Fuji transparency that I did the same way, about 1990 (Mexico):

Slides by carter3john, on Flickr

I know it is hard to see on a computer screen, but I feel that I'm improving (both slides 135 or 35mm).
 
Pocket microscopes are more convenient than loupes for this purpose - it takes enlargements upwards of 10x to evaluate grain.
 
Thanks for the info and suggestions guys! I figured needing fairly high mag., just not sure how much. Also interesting to know about the good vs. not-so good brands. I will also look into the microscope idea (never occurred to me though it makes sense)

These scans were done professionally - I've never had them turn out with huge centrally unsharp areas (only on certain frames) before so I need to track down what's going on.

Regards,
Scott
 
I use a light table 3ft x 6ft for all my light viewing/checking, with 5500-5800 kelvin blubs for proper daylight color value. The 2 loupes I favor (adjustable up to 10x) are the Pentax and Leica 10x models with the last half portion of the loupe in clear glass. You will not go wrong using either of these loupes with this design.
 
rybolt said:
If you have a 50mm lens just open it up all the way and look through the back end.
Click to expand...

+1

This would be a good first test. A fast 50 can make an excellent loupe so long as the iris defaults to full open or you can force it to open.

Certainly, you should try this before spending money and time purchasing a new loupe. A 50mm lens is equivalent of a 10x loupe. If, after experimenting with a 50mm lens, you decide to buy a loupe you will at least have a good reference point when deciding what power you need.

For critical sharpness evaluation, I generally use a 15x loupe. I also have several others with an old Nikon 7x as one of the more frequently used. At work I have an Edmond Scientific 4x that will allow a full 35mm frame to be viewed at once. This gives a nice view of a slide, but isn't the best for critical sharpness evaluation.
 
Ha - you know, I fiddled around with some reversed telescope eyepieces but didn't even think about the 50mm trick!

Excellent advice - off I go...

Scott
 
rybolt said:
If you have a 50mm lens just open it up all the way and look through the back end.
Click to expand...

Yes, a camera lens can make a fine magnifier, but the magnifying power is limited. To find the power, we simply divide 10 inches by the focal length in inches. 50mm is equivalent to 2 inches. So: 10 inches / 2 inches = 5 power. Or, do it in millimeters: 250mm / 50mm = 5x. (It's a dimensionless ratio, so the units don't matter. Just use inches / inches or mm / mm.)

You get more magnification with a shorter lens. 250mm / 35mm = 7.14x. But lenses shorter than 35mm are hard to see through!
 
Dwig said:
A 50mm lens is equivalent of a 10x loupe.
Click to expand...

No, it is about a 4,5x magnification (a little bit more).

For sharpness / resolution evaluation of my slides I am using
- the excellent Schneider 10x loupe
- a little 40x "pocket" microscope from Peak
- or my normal microscope from Bresser (40x - 100x magnification).

By the way: Pocket or normal, simple student microscopes can be bought extremely cheap new and used.

For normal viewing I highly recommend the Schneider 4x (for 35mm) and 3x (for medium format) loupes.
They are both excellent for viewing slides on a light table (outstanding quality, much much better than scans viewed on a monitor), or with the transparent foot for viewing prints.

Cheers, Jan
 
Last edited:
Rob-F said:
I also have a variable power one called the "Emoscope," which can be used at a whole bunch of powers, from 3x up to 35x. It is a little fussy to use, but if you need to inspect near the limits of resolution for Velvia, or for a scanner, you might need the magnification of the Emoscope.
Click to expand...

I agree, the Emoscope is a very useful tool. I find that using it at 15X magnification is perfect for anayzing fine grained 35mm slides to decide if something is sharp enough/ in focus.
 
LKSC said:
I agree, the Emoscope is a very useful tool. I find that using it at 15X magnification is perfect for anayzing fine grained 35mm slides to decide if something is sharp enough/ in focus.
Click to expand...

The field of view on the Emoscope/Emoskop is ridiculously narrow, though, and it is none too bright.
 
majid said:
The field of view on the Emoscope/Emoskop is ridiculously narrow, though, and it is none too bright.
Click to expand...

That's why I say it's a little fussy. That, and all the different "tinker toy" ways of assembling it. I imagine the 15x loupe Dwig mentioned might be pretty adequate, even for Velvia. A 35mm slide magnified 15x would be like looking at a print of around 15 x 22 inches, or so!
 
You must log in or register to reply here.
Back
Top Bottom