Am I expecting too much of my Nettar 515/16?

Theo Sulphate · Apr 27, 2019

Looking at some ~4x4" proof prints, made by a lab that does excellent work, I got the impression the images from my Nettar were soft. Ever since I got the camera about 18 months ago, the images always seemed soft. So I scanned the negatives at 4800x4800 dpi and the images I saw on the screen were only slightly better than the prints.

Maybe I'm expecting too much, but I've seen posts which mention the quality of the images produced by this camera (the lens is a 75mm f/4.5 Novar-Anastigmat).

So here are some samples below. The film I'm using is Portra 160 NC; it's about 18 months past its expiration date, but it's been kept in the refrigerator the whole time.

This first photo, just to give some context, is from an entire 6x6cm image reduced to 12% of its original size:

(yeah, there's dust... actually, the more I look at this one, the nicer it gets)

Again, this is just to show you the scene. I made this photo at f/11 at 1/100 second, hand held, and focus was at infinity. Now, going to 23% on the original scanned image, I present this crop of the distant hills:

The trees in the foreground seem acceptable, but the trees on the hills look soft. Maybe its color fringing and if I'd make a B&W photo they'd be much sharper.

What really puzzles me is that (referring back to the original photo) in the foreground the weeds and tractor-tread marks in the soil seem sharper than I would expect from infinity focus:

This was also at 24%.

Here is a different photo with the same exposure settings and infinity focus, cropped at 12%:

and another at 24%:

So am I expecting to see too much detail at infinity, especially with color film?

Since making these photos, I've just completed a test roll, with exposure combinations made at three different distances, at three different apertures, all from a steady rest. However, I shot the same Portra 160 NC film.

This camera is so much fun to take on trips and use that I want to find the optimal apertures and distances - or maybe I just need to adjust my expectations.

What say you?

bunip · Apr 27, 2019

It's difficoult to say if your camera is in the mean situation of every Novar 75mm lens or not. I have hundreds of folding cameras and I see that every one is different; if I test 4 samples from the same model, same lens, I'll find different results. I have so many cameras because the more you have the better you can source. Take also into account film flatness that sometimes play a big bias from time to time as you could wind your film in different ways and at different times. I wouldn't waste time and film with a novar; these are cheap and you can get a decent tessar or tessar-like (better two) for 100-150 euros each. there you'll see sharpness and have a lot of fun, but I never saw anything similar to modern lenses sharpness (say planars, xenotars or the japanese similars) even with agfa super isolette, voigtlander bessa II (heliar lens or Skopar) or super ikontas.

BMbikerider · Apr 27, 2019

There is nothing wrong with the lens fitted to the Novar lens - just don't expect Planar or even Tessar sharpness. As convenient as they are, I have always found that a 'folder' is not as easy to keep steady when shooting hand held. The lightness does not lend itself to being a very stable 'gun platform'. The other fact may be the actual focusing. I assume it is not equipped with a rangefinder and even with 'only' a 75mm lens, the depth of field is markedly smaller than from say a 50mm. Try it on a tripod at infinity with some fine detail in view and see what you get. As some one once said "I have another camera with a better lens, it was the same camera, I just used a tripod."

Having said all that, if some ham-handed amateur repairer has got his/her hands on the camera they may have done something wrong. One problem could be they have dis-assembled the lens and the focusing may have multi-start threads and all it takes to be out by one thread to upset the marked focusing points.

I would not have used colour negative film for a first film. That is inherently not so sharp as a B&W film of a similar ISO. I have used a couple of folders in the past (a long time in the past) and never found a problem with sharpness so long as I worked within what I could reasonably expect. Whatever film you use, you should still be able to get a decent 12x16 print from a 6x6 negative.

Let us know if you get any improvements.

bunip · Apr 27, 2019

Yes, look around your rear lens element if you can find any sign of DIY disassembling. That could be the problem. And I agree with BMbk about stability when shooting, even if from your pictures does not look like this being the problem.

macfred · Apr 27, 2019

Dutch Flickr user Hans Kerensky has an interesting comparison Novar Anastigmat (75mm f/3.5) vs Tessar on his site :
https://www.flickr.com/photos/29504544@N08/albums/72157620860652449/with/3690295993/
The Novar doesn't look so bad.
Kerensky's flickr is a recommendation for all who are interested in using 'vintage' cameras : https://www.flickr.com/photos/29504544@N08/collections/
I have a Super Ikonta III 531/16 with a Novar Anastigmat 75mm f/3.5 - I only did a few photographs in colour so far but I'm quite satisfied with the results .
Three examples (#1 was captured with focus on infinity at f/16; #2 and #3 are 'mid-focus' range at f/11 and f/8) :

edit: all were captured on outdated Portra 400

bernard_L · Apr 27, 2019

Theo Sulphate said:
What really puzzles me is that (referring back to the original photo) in the foreground the weeds and tractor-tread marks in the soil seem sharper than I would expect from infinity focus:

Maybe in your observations lies the answer to your own question. Possibly the focus is off.

(1) Check that front standard is parallel to film gate. How I would do it:
(1a) obtain a block or stack of plates with a size tat fits inside the film gate, and thick enough that you can...
(1b) Set up the camera on the blocks, resting on a flat horizontal table. So now the film gate is parallel to the table.
(1c) Check the table with a spirit level; need not be perfectly horizontal, only close; make a note of the deviation of the bubble in two perpe directions
(1d) Measure with spirit level against front ring of lens. If defect is found, look for signs of damage to the struts.

(2) Check infinity focus by either of these methods, with diaphragm fully open.
(2a) Rick Oleson's method. Need piece of glass (does not have to be ground glass) in the film plane, with thin lines on side facing lens. View through lens, using a known good SLR with split image spot. Both cameras set to infinity: thin lines should appear in focus.
(2b) Need ground glass in the film plane, and magnifier (could be a 50mm lens used in reverse). Aim at object at "infinity" (>=100m): tree, utility pole.... Sharp? Since your camera might be front-focusing (lens too far from film) repeat at an intermediate distance: find optimum focus, does the distance scale reading agree with actual distance? Warning: on old cameras, it's likely that the distance scale is counted from the lens, not from film plane, but if you do this test, as I wrote, at an "intermediate" distance" (say 3m) the error is not too large.

If you find a focus discrepancy, you need to reset the focus. Unscrew the (probably three) grub screws (just enough, don't lose them, and their slotted head is fragile) around the distance ring, adjust for infinity, re-install carefully the focus ring at the infinity position, tighten (not too much) the grub screws.

The links to Hans Kerensky provided by macfred show how small is the difference in quality between a Novar and a Tessar. So your camera is worth a little effort.

Theo Sulphate · Apr 27, 2019

BMbikerider said:
... if some ham-handed amateur repairer has got his/her hands on the camera they may have done something wrong. One problem could be they have dis-assembled the lens and the focusing may have multi-start threads and all it takes to be out by one thread to upset the marked focusing points.
...

bunip said:
Yes, look around your rear lens element if you can find any sign of DIY disassembling. ...

When I first got the camera, my prints revealed the rear element had been reinstalled backwards (center of the image is sharp, the rest is wildly out of focus). I couldn't remove the element, so my camera-repair friend removed and reinstalled it the correct way (he has over 30 years' experience on many cameras and does excellent work). I'm sure he tested it optically - I will show him the image plus the results of this latest test.

Another (cropped) image and a further crop from the center:

So, it seems there is general agreement the images are soft.

Ian Grant · Apr 27, 2019

One problem is the Novar lenses used quite a soft Schott optical glass for the front element, the same glass was used during the 30's for some Tessars and also the Leitz Summar, Meyer used the same glass for the Domiplan. This glass is prone to atmospheric attack by pollutants.

I have a pre-WWII Ikonta 531 with a Novar which looks very clean but is quite soft so useless, and the Domiplan that came with an Exa I is so badly affected it won't actuall focus to form an image. So I suspect your lens may have a similar issue. I was lucky and found a mint unused post WWII coated Novar in a Prontor and at some point intend to swap the lens cells so I can use the Ikonta.

Ian

AgX · Apr 27, 2019

How can a lens have a that strongly corroded front surface that it is "useless", but still "looks very clean"?

Ian Grant · Apr 27, 2019

AgX said:
How can a lens have a that strongly corroded front surface that it is "useless", but still "looks very clean"?

Essentially the surface of the lens just looks very slightly duller than you'd expect, it's not easy to spot though. In the case of my Domiplan it the front element looks like exceedingly fine etched glass and it's totally even. Jason (Nodda Dunna) has told us the exact optical glass used in another threads.

Ian

wombat2go · Apr 27, 2019

Here is my experience with the year 1936 Nettar 6 X9 with the NettarAnastigmat 1:6.3 10,5 cm.
The photos were initially of low contrast due to visible haze on the lens.
On return from lens/shutter service, the photos were all out of focus.

That was due to an element being assembled in reverse during service.
After that was corrected, the photos are good:
https://app.box.com/s/2vvkg62b2gt3lavig368

Ko.Fe. · Apr 27, 2019

You have to alling the lens. It is very easy if you have ground glass and focusing target. Do it at minimum focus distance.

Dan Daniel · Apr 27, 2019

I know I am looking at internet downloads of scans, but it sure looks to me like the dead grass and dirt is sharp while the background is out of focus slightly. Meaning that the infinity stop on the lens is off? I would check focus on the film plane.

Ste_S · Apr 27, 2019

Yup, something is up with your camera. The photos with my Nettar with the 75mm f4.5 Novar look a whole better then those

JPD · Apr 27, 2019

Adjusting the focus by using a groundglass (or a piece of plexi glass or similar with matte tape) on the film plane is a good start. For the fine tuning I tape a numbered scale like this on the lens and turn the front element to line up the mark I've made to each of the numbers and take pics. Then I study the negatives. If #5 is the sharpest I turn the mark to #5 and screw the focus ring back on. Done.

I do this fine tuning because the film bulges a bit in medium format cameras. The difference of focus on the film vs gg can be a few millimeters turn of the front element. More so on 6x9 than 6x6.

bernard_L · Apr 28, 2019

Ko.Fe. said:
You have to alling the lens. It is very easy if you have ground glass and focusing target. Do it at minimum focus distance.

If doing this at minimum distance, you need to know with certainty if the distances on the distance scale are from the film plane or from the lens. It seems that in the folder era some (most? all?) cameras had distances counted from lens. Now the standard is from film plane. See this post (read the rest of the thread for context):
https://www.photrio.com/forum/threads/folder-distance-scale-origin-point.160778/page-2#post-2092541
The distinction becomes irrelevant as one approaches infinity (if I may say so).

Besides, why would you want to do the alignment at minimum distance? Because depth of field is smaller? But what we want to align is the lens-to-film distance, and that, the depth of focus, is the same (for the same circle of confusion) irrespective of distance.

bernard_L · Apr 28, 2019

JPD said:
I do this fine tuning because the film bulges a bit in medium format cameras. The difference of focus on the film vs gg can be a few millimeters turn of the front element. More so on 6x9 than 6x6.

+1
Indeed, as seen on a S.Ikonta A, the design relies more on the position of the pressure plate than on the rails or rollers to define the film plane. However, if your camera has a red window (as a Nettar should have), you can use the Oleson method and measure the correct focus in the actual working conditions of the camera+film. Prepare a piece of film (sacrifice a frame with extra film on both sides) where you draw or scribe thin lines in the area corresponding to the red window, and insert it in the camera (without the backing paper). The red window will serve to illuminate your scribe marks; use a SLR camera as explained in my previous post. And no, the thickness of the missing backing paper is not an issue because the pressure plate is spring-mounted and makes up for the small difference.

Theo Sulphate · Apr 28, 2019

Ok... based on all this here, I spoke with my repairman, showed him the photos, and he's going to check focus, alignment, and whatever else with his optical equipment.

Thanks to all for their advice, suggestions, and samples. I will follow up to this thread with information when I get it.

Ste_S said:
... The photos with my Nettar with the 75mm f4.5 Novar look a whole better then those...

Nice funicular railway; it reminds me of Angels Flight in Los Angeles in the 1950's and 1960's:

Theo Sulphate · Apr 28, 2019

bernard_L said:
...
Indeed, as seen on a S.Ikonta A, the design relies more on the position of the pressure plate than on the rails or rollers to define the film plane. ...

I am suspicious of my Nettar's pressure plate: it seemed to be pressed flat against the back, with the springs exerting little pressure. I can actually pull it forward a bit.

I do have a groundglass and also another groundglass with small loupe attached. I will investigate the Oleson method - seems easy.

bernard_L · Apr 28, 2019

Theo Sulphate said:
I am suspicious of my Nettar's pressure plate: it seemed to be pressed flat against the back, with the springs exerting little pressure. I can actually pull it forward a bit.

Ha!
Rephrasing my previous: "the design relies more on the position of the pressure plate", the Zeiss design (at least on my S.Ikonta) seem to rely on the film's natural curvature to keep its back against the pressure plate. Now, if as you say, your Nettar's pressure plate is not even resting against the film gate rails and/or the rollers, this means that it is too far back. And so is the film. Which is fully consistent with "the foreground the weeds and tractor-tread marks in the soil seem sharper than I would expect from infinity focus" as noted by you and by Dan Daniel. If the weeds are at approx. 3m distance, a back-of-envelope calculation tells me that would correspond to the film being too far back by approx 2mm.
Why don't you try to "convince" the springs (between the pressure plate and the camera back) to change their shape, then do an Oleson test or a film test, before you resort to a professional repair? You do not even need to waste a full (B&W) film, it is possible to cut out the film (in the dark!) after a few pics, and re-attach what remains to the backing paper with adhesive tape; just remember to skip the used frames (+1) next time.

I do have a groundglass and also another groundglass with small loupe attached. I will investigate the Oleson method - seems easy.

Please re-read my post and/or google for other write-ups. The Oleson method does not involve a loupe.

Ko.Fe. · Apr 28, 2019

bernard_L said:
If doing this at minimum distance, you need to know with certainty if the distances on the distance scale are from the film plane or from the lens. It seems that in the folder era some (most? all?) cameras had distances counted from lens. Now the standard is from film plane. See this post (read the rest of the thread for context):
https://www.photrio.com/forum/threads/folder-distance-scale-origin-point.160778/page-2#post-2092541
The distinction becomes irrelevant as one approaches infinity (if I may say so).

Besides, why would you want to do the alignment at minimum distance? Because depth of field is smaller? But what we want to align is the lens-to-film distance, and that, the depth of focus, is the same (for the same circle of confusion) irrespective of distance.

Sorry, I have done it with this particularly and many other cameras, lenses. It just works. I'm not into theoretical questions and answers, my apologies. In short, if lens is aligned on minimal focus distance it will be aligned on infinity. And, obviously, it is much more easy to see if object in focus at one meter distance comparing to long distance.
Again, I'm using focusing target for it. Focus lens at one meter and put distance colar to be at the distance mark at one meter. Very easy and no theoretical threads needed .

Nettar 515 aligned on minimum focus distance:

Canadian Parliament. by Kostya Fedot, on Flickr

Theo Sulphate · Apr 28, 2019

bernard_L said:
...
Why don't you try to "convince" the springs (between the pressure plate and the camera back) to change their shape, then do an Oleson test or a film test, before you resort to a professional repair?
...

Very carefully I've pulled the plate forward. We shall see what the results are.

Now I really do suspect the plate is the source of the problem rather than the lens. When my repairman corrected the reversed rear element a year ago, I'm sure he would've tested the lens for correct focus - but of course he would've been testing it at the "focal plane" (*) with the back open and therefore wouldn't've noticed the plate was not firmly holding the film in proper position.

(*) I will have to ask how he determines this.

Ko.Fe. said:
...
Nettar 515 aligned on minimal focus distance:
...

Perfect.

bunip · Apr 28, 2019

if he uses an autocollimator he uses an optical mirror on the film plane to collimate the lens with a light going inside the camera through the lens and coming back. this way he can see lens alignment, check focus infinity etc, but on the film plane.

bernard_L · Apr 29, 2019

In another thread, https://www.photrio.com/forum/threads/folder-distance-scale-origin-point.160778/page-2#post-2174708 user alexvaras proposes just this morning the same method as I did in post #17 above https://www.photrio.com/forum/threa...much-of-my-nettar-515-16.167101/#post-2174450, maybe slightly better because he has the paper in place, in case it would make a difference.

alexvaras said:
I have done several collimation of folding cameras, some of them using a ground glass if I knew exactly where the film was placed when closing the back, if I was unsure I used the DSLR way.
I have one 120 technical film with an X draw in the emulsion side, at the same point I cut out a circle on the back paper, I load the film as usual and with the red window I position the film on that spot.
Now with the camera on T or B I put the DSLR (http://elekm.net/zeiss-ikon/repair/collimate/) as said in Mike's tutorial, but in my case I use a film loaded using the same back film plane from the camera to find out the proper distance, for helping to see the X drawn I put a flashlight at the back of the folding red window so it will be visible.
If you need more assistance let me know and I will do a set up at home of how I do it.

bernard_L · Apr 29, 2019

Theo Sulphate said:
I am suspicious of my Nettar's pressure plate: it seemed to be pressed flat against the back, with the springs exerting little pressure. I can actually pull it forward a bit.

On second thoughts, I'm not sure I understand. When the pressure plate is supposed to be pressed against the film gate, the camera is closed. Unless you remove the lens, I don't understand how you can check whether the pressure plate is pressing correctly or not.

Theo Sulphate said:
Very carefully I've pulled the plate forward. We shall see what the results are.

Not too carefully! You need to produce some permanent deformation of the leaf springs to achieve something.

Am I expecting too much of my Nettar 515/16?

Attachments

Privacy & Transparency

Privacy & Transparency