Lens choice for a particular angle of view

[Fintan]

I have a 16mp Hasselblad digital back which I haven't been using much. I've it up for sale but haven't had any takers and I'm thinking of putting it on a 5x4 camera.

Bearing in mind the sensor is 36.9mm x 36.9mm, I'm wondering what 5x4 lens would give me the same angle of view as a 50mm on a 6x6 Hasselblad?

I'm also wondering if there's any sliding digital back adapters that don't cost a fortune?

So any recommendations for a lens and sliding back and a camera to suit?

[Dave Dawson]

Regaurdless of sensor size, you want to use a lens that will give a 50mm effect on what is a format that uses 80mm as it's 'standard' lens.

Therefor 80/50 = 1.6 as the standard lens on 5x4 is 150mm 150/1.6 = 93.75 so an 90mm lens should give the same effect.
But there again.....I've ben wrong many times before !

Cheers Dave

[J. Gilbert Plantinga]

You still need a 50mm lens because you haven't changed format at all - the sensor size is the same no matter what camera you use.

[Dave Dawson]

You still need a 50mm lens because you haven't changed format at all - the sensor size is the same no matter what camera you use.

Having just given it further thought......Your right Gilbert:) Focusing a 50mm lens on a 5x4 camera will require a very deep recessed lens board!

Well I told you I'm often wrong:eek:

Cheers Dave

[Mark Barendt]

Bearing in mind the sensor is 36.9mm x 36.9mm, I'm wondering what 5x4 lens would give me the same angle of view as a 50mm on a 6x6 Hasselblad?

Actually 50mm. The sensor is not changing, so the format is not really changing, so the focal length for the same angle of view should not change.

Coverage and how much movement is available is another question. Given that 4x5 is a much larger format (~100x125) I doubt that coverage (what the lens projects) for most any 4x5 lens would be a problem.

[Martin Miksch]

about 30 mm
regards
Martin

[rugenius]

It's not about changing the lens for equivalent view.
As others pointed out already, the sensor size sees the same through any camera body if the lens is the same.

So if you used a 50mm lens before, you could use the same,...
Probably with a recessed lens board pending which 4x5" camera you would use.

Furthermore, not all 50mm lenses have the same image specification/performance.
Focal length is independent from cone of illumination, image circle, or illumination uniformity at the sensor.
To this effect, you might find a smaller or longer focal length to the 50mm lens that develops a similar image pattern at your sensor when focused at infinity, or close up.:)

[Gordon Moat]

Sometimes stitching backs appear on EBAY, often through sellers in China. Most of those I have seen only allow stitching along one plane, meaning that you could do a wider two or three capture image, but your aspect ratio on your final image would change. Depending upon the 4x5, you might be able to do a four shot capture using rear shift, and you could go up in size of final image captured area. Remember that there would be overlap needed for each stitch segment, though I think you could do four shots with a 90mm that would be similar to what you are doing now with a 50mm and one shot.

Stitching also limits what type of scenes you can photograph, though it can be great for architectural images. Sometimes there is not enough room to get the shot in one frame, or simply not a wide enough lens with you. Then a two or four shot capture that you stitch later could be a great solution.

Ciao!

Gordon Moat Photography (http://www.gordonmoat.com)

[Fintan]

I'm kindof scratching my head here and not sure if this question is answered or what to think. I know its not 50mm, and probably near 30mm, perhaps 28mm. But I'm not sure.

I've no interest in stitching, the sliding back is handy for focusing and moving the back into place, thats why I'd like to see if I can get one.

[Paul Kierstead]

Bearing in mind the sensor is 36.9mm x 36.9mm, I'm wondering what 5x4 lens would give me the same angle of view as a 50mm on a 6x6 Hasselblad?


The question is a bit unclear and somewhat confused. A 50mm lens is a 50mm lens, no matter what it is mounted on. And a 36.9x35.9mm sensor is 36.9x35.9mm sensor no matter what it is mounted on. So, assuming you actually mean is

Bearing in mind the sensor is 36.9mm x 36.9mm, I'm wondering what 5x4 lens would give me the same angle of view as a 50mm on a 6x6 Hasselblad using a 36.9x35.9mm sensor on Hasselblad and the 4x5

Then the answer is, of course, 50mm, because you are shooting on the same format. However, interpolating your question some, some of the possible questions you could be asking are:

What lens on 4x5 gives the same field of view as 50mm lens on 36.9mm x 36.9mm
What lens on 36.9mm x 36.9mm gives the same field of view as a 50mm lens on 6x6
What lens on 36.9mm x 36.9mm mounted on a 4x5 camera gives the same field of view as a 50mm lens on 36.9mm x 36.9mm mounted on a Hassy (ans: 50mm, of course, cause camera body doesn't matter)

Oh, I could likely go on ...
Anyway, since we aren't sure what you mean, you are going to get varied answers

[Gordon Moat]

A 50mm on 6x6 gives a 53.2º angle of view. Obviously that is cropped more when using a 36.9mm square sensor, since the original film area was 56mm square. You would have needed a 34mm lens to maintain the 53.2º angle of view that you would have achieved on 56mm square film with a 50mm lens.

To go from the other way, your 50mm on 36.9 square sensor gives a 39.3º viewing angle. To maintain that viewing angle on 56mm square film, you would need a 75mm lens for your Hasselblad and film. Closest choice there is actually an 80mm lens, which would be slightly cropped.

Large format is another story. I will stick with Fuji Quickload, which has an area of 95mm by 125mm. Assuming you cropped to a 95mm square final image, then here are the comparisons: to maintain that 39.3º angle of view, you would need a 124mm lens with 4x5 film, such as Fuji Quickload. If I recall correctly Fuji had a 125mm lens, though likely a Schneider 120mm would be an easier to find lens (not the macro version). If you went with the longer side of the Fuji Quickload holder, to maintain a 39.3º angle of view would require a 159mm lens, and the closest easily available would be a 150mm lens (lots of those); that would be like cropping your Hasselblad shot to a vertical composition, instead of leaving it square.

If you wanted to match 50mm on 56mm square film, assuming using film with your Hasselblad instead of the digital back, then the comparison would use the 53.2º viewing angle. A square image cropped from a Fuji Quickload would require a 79mm lens, leaving you a few choices in 75mm lens, or an 80mm Schneider. If you went for a vertical final image, then 53.2º on the long access would require a 99mm lens, leaving fewer choices on the market, though you could just settle on using a 90mm to get close enough.

All this was done using pCAM software on my Palm Pilot. As you move up in film capture area, the lens can be longer focal length to maintain an angle of view from a smaller format. If you wanted to buy a Nikon or Canon DSLR, and get what your MFDB and 50mm give you now, then you would need a shorter focal length lens, closer to a 35mm for square composition, or 50mm for cropped. Remember that your 36.9mm sensor is close to the long edge of 36mm DSLR sensors (or 35mm film).

Ciao!

Gordon Moat Photography (http://www.gordonmoat.com)

[Fintan]

I do apologise for not being clear and appreciate the replies.

OK to clarify, I like the angle of view that I see when using a 50mm lens with 120 film in a 6cm x 6cm Hasselblad. I think this is 76°45' diagonal.

If I was to put a medium format digital back which is 36.9mm x 36.9mm onto a 5x4 camera, what lens would allow me to capture 76°45' diagonal on this sensor?

[Ron Marshall]

About a 33mm lens would be needed.

Both are square formats. Assume 6x6 is about 56mm on a side.

(36.9/56)*50mm ~ 33mm

[Gordon Moat]

I do apologise for not being clear and appreciate the replies.

OK to clarify, I like the angle of view that I see when using a 50mm lens with 120 film in a 6cm x 6cm Hasselblad. I think this is 76°45' diagonal.

If I was to put a medium format digital back which is 36.9mm x 36.9mm onto a 5x4 camera, what lens would allow me to capture 76°45' diagonal on this sensor?

http://www.schneideroptics.com/ecommerce/CatalogItemDetail.aspx?CID=1325&IID=1886

or the equivalent from Rodenstock, though the Linos website is down for maintenance currently. I did find that ALPA have that lens in a helical mount, with some specifications for you to compare it to the Schneider:

http://www.alpa.ch/index.php?path=products/lenses/adapted_alpa_lenses&detailpage=154

Check the PDF document links for specification on the lens. Also, ALPA have an XLS (Excel file) Comparable Focal Length Calculator on their website:

http://www.alpa.ch/knowledgebase/search/Comparible+Focal+Length+Calculator

What I would suggest is sticking to a camera which allows shift movements, rather than going with a regular 4x5 camera. Only some 4x5 cameras would be appropriate for such ultra short focal lengths, and your movements are very limited by the lack of coverage of the lenses.

Ciao!

Gordon Moat Photography (http://www.gordonmoat.com)

[Fintan]

ah thats great thanks

[John NYC]

A 50mm on 6x6 gives a 53.2º angle of view.

Gordon Moat Photography (http://www.gordonmoat.com)

Slightly irrelevant to the OP, but how are you getting 53.2 degrees?

[GPS]

A 50mm on 6x6 gives a 53.2º angle of view.

...


I do apologise for not being clear and appreciate the replies.

OK to clarify, I like the angle of view that I see when using a 50mm lens with 120 film in a 6cm x 6cm Hasselblad. I think this is 76°45' diagonal.

...

50mm lens on a 6x6 film format makes 61.9° view angle ...:)

[GPS]

50mm lens on a 6x6 film format makes 61.9° angle view...:)

The equivalent angle of view on a 36.9mm sensor is a 31mm lens.

[John NYC]

50mm lens on a 6x6 film format makes 61.9° view angle ...:)


Slightly irrelevant to the OP, but how are you getting 53.2 degrees?

Correct trig if you used 6x6 cm for size. Medium format film is 56mm on a side, yielding a 58.498 degree angle of view (horizontal or vertical) with a 50mm focal length.

If there are any doubts still with all the various answers, here's a really handy website, but too bad it doesn't do LF.

http://www.sweeting.org/mark/lenses/medium_format.php

[Gordon Moat]

Slightly irrelevant to the OP, but how are you getting 53.2 degrees?

While I was jumping around in settings in pCAM software, somehow I got the camera to subject distance down to 0.297m

[GPS]

Correct trig if you used 6x6 cm for size. Medium format film is 56mm on a side, yielding a 58.498 degree angle of view (horizontal or vertical) with a 50mm focal length.

If there are any doubts still with all the various answers, here's a really handy website, but too bad it doesn't do LF.

http://www.sweeting.org/mark/lenses/medium_format.php
Unfortunately, you're not as correct as you think you're...
Different medium camera types have different actual film frame size. Thus one camera can indeed have 56mm film gate while the other has 57mm. The differences are even bigger on the horizontal side. The OP didn't specify the actual film gate size on his Hasselblad, hence...
The same is valid for LF. Therefore when citing view angles the nominal film sizes are usually taken for calculations unless one is interested in the actual values and takes the precise actual film gate values for it.

[John NYC]

Unfortunately, you're not as correct as you think you're...
Different medium camera types have different actual film frame size. Thus one camera can indeed have 56mm film gate while the other has 57mm. The differences are even bigger on the horizontal side. The OP didn't specify the actual film gate size on his Hasselblad, hence...
The same is valid for LF. Therefore when citing view angles the nominal film sizes are usually taken for calculations unless one is interested in the actual values and takes the precise actual film gate values for it.

Which is why I said your answer is correct if you use 6x6cm. That is, you are using the same math I am.

The website I showed uses 56mm on a side also, and that is what I've usually seen quoted as the typical actual size.

[John NYC]

While I was jumping around in settings in pCAM software, somehow I got the camera to subject distance down to 0.297m

Not sure I'm following you.

[Gordon Moat]

Not sure I'm following you.

Angle of view changes slightly with focus distance. If you only did calculations at or near infinity focus, then the numbers might be more consistent. Anyway, I only used pCAM to come close to the lenses that might match the needs of the OP, and then wrote about which choices might be easily available.

[John NYC]

Angle of view changes slightly with focus distance.

Ah, didn't realize that.