Review of eTone Ultra Bright Fresnel Lens

[_T_]

I just received and installed an eTone fresnel on my Cambo SC. I haven't seen many reviews of this fresnel so I wanted to give what first impressions I have.

The fresnel pattern doesn't interfere with my ability to see small details on the ground glass and doesn't impede focusing with or without an 8x loupe. The pattern is very fine so that it's almost invisible except for the slight reflections it produces from stray light hitting the viewing side of the glass, which go away when using a dark cloth.

I pointed my camera at a light source and used a spot meter to measure the brightness of the same square on the grid of my ground glass with and without the fresnel and I was pleasantly surprised. eTone claims an improvement in brightness of 1-2 stops, but with all of my lenses it outperformed this spec. The least improvement I saw was 3 stops brighter than the ground glass alone, and with my Fujinon WS 180mm f/5.6 I saw an improvement in brightness of 5 stops.

I am blown away with the improvement. Composing is so much easier, the image on the glass is clear and bright from edge to edge with my Fujinon SWD 90mm f/5.6. Where once I struggled to position my eye correctly in order to be able to clearly see objects in the corners and edges of the glass, now I can see the entire image clearly from a single position, no need to bob and weave to catch the light.

I did find that the clipped corners on the fresnel were rather small. They did not allow me to sight the aperture through the clipped corners of the ground glass, but I was able to fix that quickly with a pair of scissors. I used the ground glass itself as a template so now the fresnel is exactly the same size as my gg.

I'm quite happy with my purchase and at about $40 usd with free shipping it was a steal compared to many of the products offered by some of the major camera manufacturers.

When I have more time and experience with the eTone I will come back with further thoughts and give an opinion on it's longevity.

 

[BrianShaw]

Excellent review and personal experience. That is a very astonishing brightness improvement; almost unbelievable! I've been happy with my Dave Parker Satin Snow ground glass for years but changing eyes could make this upgrade desireable. eTone products, in general, have met my needs as high quality and affordable.

 

[blee1996]

Thank you for the detailed and informed review! I am currently researching fresnel lens for my older 4x5 and 8x10 camera, and this is really helpful.

 

[Dan Fromm]

Interesting. The description on etonephoto.com says that the fresnel goes in front of the ground glass. Shouldn't this more the focal plane?

OP, what's your experience? With the fresnel in place is the film still in register with the gg?

 

[BrianShaw]

Interesting. The description on etonephoto.com says that the fresnel goes in front of the ground glass. Shouldn't this move the focal plane?

OP, what's your experience? With the fresnel in place is the film still in register with the gg?

I'd assume so, except perhaps with some of the Speeed Graphics. I assumed that was misguided and incorrect. Hopefully the buyers/users know better.

 

[blee1996]

Interesting. The description on etonephoto.com says that the fresnel goes in front of the ground glass. Shouldn't this more the focal plane?

OP, what's your experience? With the fresnel in place is the film still in register with the gg?

I was about to ask the same question after reading the description on eTone ebay listing. And I also think that is incorrect, since it will shift the focal plane which will not agree with the film holders.

 

[_T_]

Interesting. The description on etonephoto.com says that the fresnel goes in front of the ground glass. Shouldn't this more the focal plane?

OP, what's your experience? With the fresnel in place is the film still in register with the gg?

The placement of the fresnel will depend on the particular camera on which you wish to install it and the dimensions of the fresnel.

If your camera is designed to have a fresnel installed in front of the ground glass, i.e. on the inside of the camera, but it doesn’t currently have a fresnel installed then it might be possible. You would have to check if there are shims holding the gg at the correct T distance, then you would have to compare the measurement of the shim(s) thickness to the thickness of the fresnel you want to install. If the fresnel is the same thickness as the shim you can just remove the shims and pop it right in, if it’s thinner you will need to find the right shims to increase the T distance, if it’s thicker than the shims you cannot install the fresnel in front of the gg. If there are no shims then your camera probably isn’t designed to have a fresnel in front of the gg.

My Cambo is not designed to have the fresnel in front of the gg so I had to install it on the back of the ground glass, in other words on the viewing side. On my SC it’s a fairly simple matter of loosening the ground glass clips slightly, sliding the fresnel under them and tightening them back down. Some cameras have different systems for holding the fresnel in this position, for example some require that a notch be cut on each of the short ends to accommodate the gg clips which do not have the travel to hold both the gg and the fresnel. The plastic is easy enough to cut that you should be able to find a way to cut notches if you need to but I can’t give a recommendation. All I can say is it seems too chippy to do it with scissors. You would end up with a jagged sort of partially shattered edge if you did that.

As for the direction in which the fresnel should face, after much research it’s my understanding that the fresnel should face with the ridged side facing the ground glass whether it’s in front of or behind the gg.

It appears that the fresnel will work in either orientation if installed on the outside of the gg but that it would be undesirable to have the delicate ridges facing outwards where they can be more easily damaged. I don’t know if the fresnel would work in either orientation on the inside of the gg or why it’s recommended that the ridges face the ground glass when it’s placed on the inside of the camera, only that all the sources I can find agree that this is the correct way.

Being plastic the fresnel is more prone to wear than the ground glass. For that reason I intend to report back on the wear and tear I find after using the fresnel several times. I just received a box of HP5 and I intend to return with further information after the entire box of 25 sheets has been shot unless I find that the fresnel has worn significantly before I reach the end of the box.

 

[Dan Fromm]

In other words, the vendor's directions are wrong.

 

[pdccamerqs]

Hi T,

Great review and update. I just received two 4x5 Etone fresnels, one in "graphic" size for speeds and crowns, and one for most other 4x5 cameras. The fresnels for the graphics are little larger in length and width. I will be installing the smaller "regular" fresnel on an Intrepid 4x5 this weekend.

I will install it on the inside of the camera, with the smooth side facing the lens. I have had many fresnels on many cameras from Kodak Reflexes, to Graphics, to Calumets (Cambo) and more - and some I have mounted on the lens side and some on the photographer side. I have never had any problems with focusing . My understanding, and please correct me if I am wrong, is that the side you mount the fresnel on (ie. on the photographer side or on the lens side of the ground glass) makes no difference, as long as you don't change the position (distance) of the ground glass relative to the lens.

Best of luck with the HP5!

Paul

 

[Doremus Scudder]

In other words, the vendor's directions are wrong.

That certainly seems to be the case. Maybe the OP can let the vendor know about this thread and the error. If the product is good, it might increase sales.

Doremus

 

[_T_]

My understanding, and please correct me if I am wrong, is that the side you mount the fresnel on (ie. on the photographer side or on the lens side of the ground glass) makes no difference, as long as you don't change the position (distance) of the ground glass relative to the lens.

Best of luck with the HP5!

Paul

Yes that’s true. If you can find some way to install the fresnel without moving the ground glass you can put it on either side of the glass and there may be other ways to do this that I haven’t considered. If you can figure a way to put the fresnel on the inside of the camera that would be preferable but it’s not always possible.

And thanks!

That certainly seems to be the case. Maybe the OP can let the vendor know about this thread and the error. If the product is good, it might increase sales.

Doremus

I think that eTone might be relying on the consumer to research the matter. There is quite a lot of information on the subject and much of it is dependent on the equipment that the consumer intends to use the fresnel with.

I think that giving a comprehensive overview of the subject on the product page could be confusing and deter sales.

And on the amount of improvement in brightness reported by eTone: the performance of the fresnel in this regard is dependent on the lens it’s being used with. The numbers that eTone lists are likely conservative estimates intended to keep customers from being dissatisfied, and they may be accurate with certain lenses.

These are part of the reason that I decided to make this thread. In order to make a place where all of this info can be easily found when looking for information about the product.

 

[abruzzi]

My understanding, and please correct me if I am wrong, is that the side you mount the fresnel on (ie. on the photographer side or on the lens side of the ground glass) makes no difference, as long as you don't change the position (distance) of the ground glass relative to the lens.

My understanding is a fresnel between the lens and the ground glass, will affect the focal position of the ground glass by about 1/3 the thickness of the fresnel. Admittedly, I've seen this mentioned on forums by relatively knowledgeable members, but I haven't seen anything "official" from camera makers or published papers.

 

[Dan Fromm]

I think that eTone might be relying on the consumer to research the matter. There is quite a lot of information on the subject and much of it is dependent on the equipment that the consumer intends to use the fresnel with.

I think that giving a comprehensive overview of the subject on the product page could be confusing and deter sales.

I see. Let the buyer beware.

By the way, the problem I raised is entirely independent of the camera in which the eTone fresnel is mounted. If the focusing panel is designed for a fresnel the same thickness as eTone's, fine, wonderful. Otherwise the buyer will be in trouble.

 

[_T_]

My understanding is a fresnel between the lens and the ground glass, will affect the focal position of the ground glass by about 1/3 the thickness of the fresnel. Admittedly, I've seen this mentioned on forums by relatively knowledgeable members, but I haven't seen anything "official" from camera makers or published papers.

You can use this formula to calculate exactly how far off your focus will be if you move the T distance to install the fresnel:

1/f - 1/BellowsExtension = 1/SubjectDistance

I just took calipers to a chunk of the fresnel I cut off and it’s 0.8mm thick.

So if I were to move my T distance by the thickness of the fresnel and focus my 90mm lens at a distant object, say 10m, then I would have this formula

1/90mm - 1/B.E. = 1/10,000mm
B.E. would therefore normally be 90.82mm but with the t distance being off by 0.8 you would actually have 90.02 which we plug back into the formula:

1/90mm - 1/90.02 = 1/S.D.
Subject distance would then be 405,090mm or 405m meaning you’d be off on your focus by almost half a km. Meaning you wouldn’t be able to trust the focus on your ground glass at such subject distances.

So you can see 0.8mm can have a significant impact especially when focusing on distant objects.

For the record this is idealized slightly. In practice you would have to account for the flange focal distance of the lens but the illustration is still useful.

Edit: Excuse me I flipped a sign with that explanation it’s been corrected now