90mm f6.8 vs f8 lenses

[Meekyman]

Hi Folks,

I am relatively new to LF photography.

When it comes to a 90mm lens, is there really a difference between a f6.8 and f8 when it comes to focussing? I can understand that at the maximum aperture one might be brighter than the other, but surely as you stop down to determine where you have all that you want in focus, this difference disappears or am I misunderstanding something?

I'm into landscapes, so would be looking at early dawn and have a good darkcloth. Would that f6.8 make the experience so much better? I think a f5.6 would be too heavy what with the rest of the gear for me.

Cheers

Graham

[Kevin Crisp]

The 6.8 part of the question makes me think you are considering one of the Angulons. They have limited coverage for 4x5 and some of the early ones I have used really aren't sharp to the edges even with no movements. F:8 90's, like the Nikkor, have lots of coverage which is a big plus to most people. To answer your question on focusing, I don't think the f:8 lenses are hard to focus, you should be using a loupe with either since it is so easy to be off if you eyeball a wide angle.

[Michael Graves]

As Kevin points out, the most significant difference is not in how brightly they throw an image. It is a relatively small difference. What Kevin didn't point out is the HUGE difference in size. My 90mm F8 is about the size of a small brick, whereas the 6.8 is a tiny little gem that fits into the palm of my hand with ease. My particular lens is sharp out the edges, but as he aptly mentions, the coverage is just enough for 4x5. No spare coverage for movements. It's a great point and shoot W/A for a Speed Graphic, but not much for architecture.

[Bob Salomon]

The 6.8 part of the question makes me think you are considering one of the Angulons. They have limited coverage for 4x5 and some of the early ones I have used really aren't sharp to the edges even with no movements. F:8 90's, like the Nikkor, have lots of coverage which is a big plus to most people. To answer your question on focusing, I don't think the f:8 lenses are hard to focus, you should be using a loupe with either since it is so easy to be off if you eyeball a wide angle.

What about the very current Rodenstock 90mm 6.8 Grandagon-N?

There is more then the Angulon available.

[Drew Wiley]

I greatly prefer an f/4.5 90 for its interior architecture options, esp when moving the camera about with a center filter in place, and for analogous work in ruins, caven entries etc. For more ordinary landscape work in full light, an f/8 lens wouldn't make much difference and would be more portable anyway. The need for coverage is also related to subject matter. Angulons
don't have much wiggle room, while most of the modern 90's have tons.

[Oren Grad]

What about the very current Rodenstock 90mm 6.8 Grandagon-N?

There is more then the Angulon available.

What Bob said. There's a whole series of f/6.8 Grandagons - 75, 90, 115, 155, 200. These are modern designs with large image circles. I've used the 75, 90, 115 and 155. They're fine lenses that, overall, offer a nice balance of cost/size/weight/optical performance for their respective focal lengths and coverage angles. The Super Angulons, Nikkors and Fujinons are good lenses too. Based on experience with the Grandagons as well as with many other lenses with both larger and smaller maximum apertures, I wouldn't worry about the difference between f/6.8 and f/8 - just look for whatever lens seems to offer the best value overall for you.

[Meekyman]

Hi everyone,

Sorry for any confusion...I was talking about the Rodenstock (Caltar) Grandagon f6.8 90mm lenses indeed vs, for example the Nikon/fujinon f8.

So, the feeling is then that the focussing difference between the f6.8 and f8 lenses is minimal? How is much difference in flare control across the Rodenstock/Nikon/Fujinon 90mm offerings? Any other differences, other than coverage/weight, I should be aware of? I currently own two Rodenstock lenses (135mm f5.6 and 210mm f6.8) and am happy indeed.

Cheers

Graham

Cheers

Graham

[Larry Gebhardt]

I had a 90mm f/8 Super Angulon. It was nice and small, but I had trouble focusing it. I now have the Caltar version of the f/6.8 Grandagon. It's a bit brighter, has more coverage, and works well for my needs. I have not compared it to the Nikon. I think it's an excellent choice, but I have not extensively compared all the 90mm lenses out there.

A fresnel lens for the ground glass is very helpful with 90mm and other short lenses. It makes much more difference than the 1/2 a stop between the two lenses in real visibility.

[Peter Yeti]

Graham,

I use a Sinaron-W 6.8/90 (which is a Rodenstock Grandagon-N) with my Linhof Technika and a Super-Angulon XL 5.6/90 on my Sinar. The SA XL is a brick! It is brighter for focusing and has much larger coverage than the Sinaron/Grandagon but I only use it when this coverage is really an issue. For everything else I use the Sinaron, which is an outrageously good lens. 6.8 is 1/2 f-stop darker than 5.6 and 1/2 f-stop brighter than f8. You can try with one of your lenses whether or not a 1/2 f-stop matters for focusing. Unfortunately, I don't have experience with Fujinons or Nikkors which I could share. I also would pay attention to the availability of a suitable centre filter.

[dave_whatever]

I've used a Fuji 90/8 and currently own a super angulon 90/5.6 and a rodenstock grandagon 90/6.8. The difference between the fuji and the SA in terms of brightness is immediately noticeable, the difference between the 6.8 and the 5.6 is less pronounced. Whichever lens you have the fresnel and ground glass you're using makes more of a difference than the difference between lenses in my experience. A darker f/8 lens with a good fresnel/GG is more than usable, although granted a 5.6 lens is easier to focus wide upon due to the decreased depth of field.