Nikon SW 75mm f4.5 Lens Test, Vignetting, and Surge Marks (?)

This is a long rambling post. You have been warned...

A New 75mm f4.5 Lens

The Lens Nikon 75mm f4.5 SW

I bought a 75mm lens for my Intrepid 4x5 fof eBay from Japan. My motivation was to replace my much heavier 90mm Fujinon SWD lens. It is a technically great lens but has much more movement than I need and weighs more than my other lenses.  

Now I have purchased 3 similar lenses (90mm, 150m, and 210mm) along with my Fuji GW690III all from Japan through eBay with no trouble. Each was in excellent working order and excellent condition. 

This time, however, my experience was different. I waited a week or so for shipping and to clear customs. (In the UK you pay about 20% VAT which FedEx invoiced me for.) The lens arrived well packed, and I opened it up and found it looked to be in immaculate condition. No scratches in the paint or signs of wear were evident on the lens body. The glass was in excellent condition. I fired the shutter at each speed, and they sounded correct. The lens came with a lens board that I had guessed would fit the Intrepid given the description. I went to mount the lens and moved the aperture blades, and this is where things went wrong. Some of the blades (2 or 3) seemed out of place and indeed as I moved the aperture lever some of the blades were mispositioned and sometimes wouldn't move at all. You can imagine my disappointment. 

I contacted the seller and sent photos of the fault and he asked if I could send the lens for repair. I inquired and replied what the charges might be, and he approved the cost. I sent the shutter off to Linhof Studios in Southend UK as this got some recommendations on Photrio. 

When the lens arrived, they said there was damage on the corner of the lens board and sent photos of it. It was clear the lens had been dropped at some point before it was shipped. They carried on with the repair about a week later and reported that the frame of the shutter had cracked in two places. As such they would not warranty the work as they could not say how long the repair they attempted would last. The blades were put back in place and one they had to straighten slightly. (An important thing to know if you do break a lens is to realize that if the aperture blades as messed up do not move and certainly do not force the blades. The repairperson said this was a frequent problem and shutter leaves are about £18.75 each to replace.) Linhof Studios was quite good and only charged their minimum charge. 

I contacted the seller and asked for a refund for the cost of the lens, the repair cost, shipping to and from the repair center and the VAT I was charged. I submitted all the documentation from the repair and all the invoices. After some back and forth while the seller came to understand what happened he offered to refund the lens cost and let me keep the lens for the cost of VAT and the repairs. I accepted this compromise. The lens works but who knows how long, I think of it as renting it for some unknown period. I expect it will break again if jarred slightly. The lens board fits my camera exactly and has some nice features that would be useful if I must replace the lens in the future. A straight lens board is at least £30 from Intrepid and recessed lens boards are worth more. 

This experience made me realize how delicate the shutter is especially when the glass is mounted, and the shutter is mounted on the lens board. If the lens is dropped there is a good chance it will land on the lens board. With the glass having the largest mass this means the shutter takes an enormous force if it lands on the lens board. The frame of the shutter is not strong and hence considerable damage can occur. 

Lens Test

So next I took it out to test it. I wanted to try it out but also wanted to see if I would have trouble with my square filter holder. The concern is I need to screw in a 67mm adapter to the lens to attach the filter holder and there is the possibility that the holder might interfere with the image from the lens. I also wanted to see the amount of vignetting to expect from the lens as such a wide lens is expected to have some. 

I took the lens out to Fen Drayton which is close by and offers some landscapes that are more interesting than my back garden. It was a very cold and windy day, not very enjoyable. I setup at the end of a lake and made two images with my 2 stop GND filter. The first was wide open at f5.6 (1/15th sec) and the other stopped down at f32 (to keep the exposure at the minimum shutter speed of 1 second).  This was meant to reveal how much vignetting occurs on the lens. 

I composed the image to expose as much sky as possible. One obvious limitation of a short focal length lens is that movements are very restricted by the stiffness of the bellows. The traditional solution is to use a bag bellows which is more flexible. 

I returned with these two images and then set about developing using HC-110 dilution B in my adapted Cibachrome drums I use as a rotary processor. I learned a few interesting things. 

First the images

f5.6 1/15th

f32 1 sec

There is distinct vignetting in both images in the upper corners with it being more pronounced in the wide-open image which is consistent with the way vignetting and lens coverage works. However, the vignetting appears only in the upper corners of the image. This is due to the movement that placed the lens at its highest point. Since the image is inverted on the film plane those corners are at the limits of the lens coverage.

I see no evidence the filter holder is causing any trouble which is great news.

Surge Marks? 

The next observation was unexpected. The development is uneven. Most notably in the second image with the bright vertical band in the center of the sky and a lesser one near the left edge. There is also more subtle horizontal banding in the sky as well. The first two vertical bands are almost certainly surge marks. I encountered these when I made the film holders, I used to hold the 4x5 negative against the wall of the tank.

I cut out and fold small plastic tabs along three edges to help keep the film in position during development. These tabs were quite long, and I got surge marks as a result it seems of the turbulence they cause. I cut these tabs shorter and modified the motor control to reverse direction after a rotation and a half to ensure more even development. (Blog post on this here...) 

After I made these changes, I did not see any more problems for a couple of years. Reading up on online forums these surge marks can come and go for no apparent reason except that some change has been introduced. I don't know if my case is because I am using FP4+ film for the first time in a long while or that because the images have large sky gradients the surge marks are more apparent. 

What I do know is the two light streaks correspond exactly with the position of the shortened plastic tabs. So, I made them shorter. The more subtle banding could be surge marks from the edge of the film I suppose setting up some wave pattern as the film is rotated in the drum. In any case I plan to try to double the volume of developer so rather than 265ml of dilution B I will use 500ml. I hope this might lead to more even development. 

Next, I plan to test a few things out from the list below. 

• Not so much vertical movement to confirm source of vignetting. 
• Try the G617 center filter. 
• Try a larger amount of developer (500ml)

Next Tests

I made two more images nearer my home with Mollie out for a walk. I setup on the bank of the Ouse which turns out to be a swan's landing area. The swan took some umbrage with Mollie and spent some time hissing while she bravely sniffed and investigated from her position on shore. After a minute, some kind of truce was negotiated, and the swan continued to calmly observe us while Mollie grew bored of the swan. 

I made two images on Ilford FP4+ again. This time I aimed to keep the rise of the front standard less and so opted for about 1/3 of the full possible rise before the lens interferes with the bellows. Both images were exposed at f5.6 almost wide open. I did not use my GND this time to keep it simpler.

The first image I made without the center filter from my Fuji G617. This was f5.6 at one-eighth second. I used the tree trunk as the zone V metering spot. 

I then used the center filter with a 67mm to 77mm adapter. The aim was to see if it would be useful in attenuating any vignetting. I had to compensate for the center filter by a full stop, so this was f5.6 at one-fourth second. 

The day was very gray and overcast with little detail in the clouds. The sky is perhaps a little overexposed. I placed the two images side-by-side with just inversion and setting the black point. The image on the right was without the center filter and I had to lighten it slightly to try and match the tone of the tree trunks so a like-for-like comparison would be more easily made. The image on the right does have a slight vignetting and the center filter cleans it up on the image on the left. The vignetting is not so strong as to be a blemish the image, however I would be inclined to use the center filter with chrome films as the higher contrast shows vignetting much more effectively. 

Left Center Filter f5.6 1/4 second Right No Center Filter f5.6 1/8 second

The other experiments revolved around resolving the surge marks during development the previous day. I trimmed shorter the tabs that hold the film into place on my mylar holder. The image on the left I also developed in 500ml of dilution B (HC-110) rather than the 265ml I used last time. I see no more surge marks. With this in mind I developed the image on the right with 265ml of developer and again no evidence of surge marks. 

It seems trimming the tabs helped though as I have seen from other's experience that this issue can come and go for no apparent reason. I am a little wary that the sky is much denser on these most recent negatives and so it may only be apparent on less dense parts of the negative. There may yet be more experiments to nail down this issue for good. 

Conclusions

The lens works well, and I like using it more than the 90mm. The 90mm has such a large rear element (74mm vs 54mm) that even though it is longer focal length it has more restricted movement due to interference with the bellows than the 75mm. The 75mm is also 187g (6.5 oz.) lighter at 420g (14.8 oz.) vs 607g (1 lb. 5 oz.).  

The coverage is less however at f16 it is 200mm while the Fuji 90mm SWD is 238mm at f22. The 75mm coverage shrinks to 126mm at max aperture which corresponds to my first tests and vignetting I see with lots of vertical rise. The horizontal angle of view is a difference between about 74 degrees on the 75mm and 65 degrees on the 90mm lens.

A general complaint about 75mm lenses and shorter focal lengths is how well they work on any given camera due to the short focal length. I have the Intrepid MK3 camera with an upgraded focus platform from the MK4 which is hugely more convenient. The 75mm lens focuses on infinity with some room to spare on the closest mounting point for the standard. The lens I bought came with a recessed lens board which certainly helps, and the lens and lens board accommodate the recess well. 

The lens board has a cable release socket that couples to the lens shutter release so my fat fingers can easily thread the cable release on. The shutter open/close switch has a raised stud. 

Recessed lens board. Cable release socket on right. 
Note raised shutter open/close lever on left. 

On the bottom of the lens the aperture adjustment is also raised out of the recess for easy access. All of these make the lens no more difficult to operate than any other large format lens I have. 

Raised Aperture Lever

Too Wide?

There is one issue with the 75mm lens that does not happen with the 90mm lens. In the lowest front standard fall position (shifted to the bottom of the front standard range) the front of the camera comes into view (especially in portrait orientation). This is problematic as this Intrepid (MK4 base) does not have the means to move the rear standard forward. The Intrepid Mk3 base had some small movement and swing which might have helped (but I cannot verify). Some cameras have a front drop (My previous 4x5 camera an MPP MKIII had this and needed it for an 89mm lens I had.) 

I do not this is a real issue for me or not. I cannot really recall ever using front standard fall movement in a shot. I typically use rise from my recollection. There are a few ways around this. One may be to lower the tripod head to adjust the composition. There is also the ability to tilt the rear standard back, raise and tilt the front standard back to be parallel. This leaves the plane of focus pointing upwards. You then lean the tripod forward to compensate for this.

The angle of view is 74 degrees, If I project half this angle (37 degrees) from the plane of the lens board as an estimate for the nodal point that line does intersect the camera front just before the furthest lens mount point which corresponds to what I see on the ground glass.  

This problem becomes worse in portrait mode versus landscape. Fortunately, I shoot most of my images in landscape. In landscape the problem surfaces about 6mm away from max fall distance. In portrait this moves to about 15mm which is actually a slight rise from center (12mm).  experience will tell if this becomes a serious limitation. 

(NB: The lower fall is limited by the height of the knob used to attach the front standard to the bed of the camera. The slots in the standard go lower than this but cannot be bottomed out because of this knob. This leaves about 80mm of slot in the upward direction.)