Loupe question

[Raffay]

Hello, I am using a 128mm enlarging lens to act as a loupe but with a 127mm lens on the camera I am still finding it difficult to focus on my subjects eye. I know 127mm is way too short for portraits but this is the only lens I have right now. I was looking at this loupe on freestyle photos that says 10x magnification. I wanted to know how magnification factor is calculated for example what magnification factor is my lens providing and whether this loupe from freestyle be a substantial increase in magnification - it is for almost 40 dollars.

Any help would be appreciated.

Cheers
Raffay

[vinny]

10x is too strong as you'll be viewing the grain of the ground glass. I prefer 6x from Peak.

[Ari]

I normally use a 5x Peak loupe, but switch to a 10x for wide-angle work; I find it harder to achieve precise focus with wides using only a 5x.
Vinny's right, though; at 10x, you get a lot of the GG grain.

[C. D. Keth]

I use an 8x. I don't think 10x is too strong if that's what you happen to have. It will work. 4x to 8x is kind of the sweet spot for most people.

[Raffay]

Thank you for your inputs, however, I want to know the comparison between what I am using and this one, so that I don't spend money on something that I already have. Where can you order this peak brand from?

Cheers
Raffay

[Doremus Scudder]

I use 8x or 10x. I like the extra magnification.

Best,

Doremus

[Michael W]

I've been using one of the Peak 5x magnifiers. About $14 from B&H. Good quality for a plastic magnifier and longer than most so I don't have to push my face up against the ground glass.

[vinny]

Sorry, i must be using a 4x. Where to find it? B&h, or any other online photography store. Try google.
http://www.peakoptics.com/index.php?main_page=product_info&cPath=65&products_id=103&zenid=f506ca1585ef31a39da8c59752dc32f2

[John Kasaian]

The cheap Agfa type 9x loupes (less than $8) do all right plus they'll multi task when louping your negatives. Upgrade to a nicer Toyo or Silvestri if you really want to spent the extra $$. My 2-cents anyway.

[Leonard Evens]

Some googling suggests that the formula for magnification is either
250/f or 250/f + 1
depending on how the loupe is used. Here f is the focal length measured in mm. (250 mm is the location of the unaided near point for normal eyes for young people.

250/127 is about 2. So you "loupe" is providing between two and three times magnification. This would be too little to see much detail for a wide angle lens or any lens used in closeups. You should try something with a magnification of 8 X to 10 X, but even 10 X will be hard to use because it will show surface detail on the gg, which may be difficult to distinuinguish from image detail.

Of course, you would have so much depth of field in such circumstances, that critical focusing my not be all that important.

You should look up advice about how to focus in closeups. Oftne, you should move the camera rather than hte lens. This is described elsewhere in the large format site.

[C. D. Keth]

How is moving the camera and changing a chosen frame an acceptable method of focusing?

[E. von Hoegh]

How is moving the camera and changing a chosen frame an acceptable method of focusing?

Moving the entire camera allows you to focus without changing the reproduction ratio, it's a technique used when making extreme closeups (which the OP is not, he's making portraits).

[C. D. Keth]

Very, very few people care about being precisely 1:1 or any other reproduction ratio. Most people are much more concerned about a particular composition.

[E. von Hoegh]

Very, very few people care about being precisely 1:1 or any other reproduction ratio. Most people are much more concerned about a particular composition.

When you're taking a picture of (for instance) a damaged pivot (from a pocket watch) .020" in diameter, and filling about 1/4 the short dimension of a 35mm frame with the image, it's much more convenient to move the entire camera because moving the lens alone changes the lens/film distance, lens/subject distance, and reproduction ratio. I did say it was used in extreme closeups.

[E. von Hoegh]

For the OP, there are certain advantages to using a proper loupe for focussing. It's important to set the loupe so it is focussed on the texture of the ground glass, and the loupe will be much more convenient than holding a lens the required distance from the gg. Most prefer a 6 to 8 power loupe, a 10 power loupe really is best on a finer than usual ground glass.

[ac12]

I have what I think is a 8x loupe (looks like a Peak 8x, but has a Nikon label) and I do see a lot of the ground glass grain on my Toyo 45D.
Should I drop down to 5x when using my 150mm lens?
I don't have a lower power loupe so I don't know the visual effect.

The tall 5x Peak does look interesting, like looking at a 20x25 print.
I had to go to the Peak web site to get the size of the loupe. 35mm diameter x 66mm high

[Maris Rusis]

I choose the power of a loupe on considerations of the final enlargement ratio of the negative.

If I'm going to enlarge a 4x5 negative to 16x20 that's a 4x enlargement so the focussing loupe power needs to be greater than 4x to give me reserve focussing accuracy. If I'm focussing an 8x10 camera with a view to contacting out the negative I don't need a loupe at all; just some strong reading spectacles. The principle is that I need to focus finer than I can see.

[C. D. Keth]

If I'm focussing an 8x10 camera with a view to contacting out the negative I don't need a loupe at all; just some strong reading spectacles.

Why not focus all film at all sizes with the same fine standards? What if you want to enlarge that negative later? I'd hate to do it and just find it didn't hold up because I was lazy with my focusing at the time of exposure and introduced error.

[Ari]

After reading this thread, I decided to bite the bullet, and I ordered a 12x loupe from Edmund Optics (http://www.edmundoptics.com/microscopy/magnifiers/comparators/transparent-base-magnifier/30-055).

It was recommended to me a while back, but I resisted buying a $60 loupe.

But I've had too many wide-angle shots look soft when I scan and go to full size; it is always a disappointment.

[irwinhh]

A entire set of different magnification loupes can be purchased at Harbor Freight for less than $5.
Pick the one you like and toss the others!