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Digital cropped sensor and lens hoods

simonpg

New Member
Here is a question that came to mind although I am not a digital shooter.

If one is shooting on a cropped sensor camera/back with a conventional full frame lens, should one use a longer focal length lens hood to maximise contrast etc?

Think about it: using a wider angle lens like a 60mm V series lens with a CFV digital back with a 1.5 crop factor means you get an equivalent angle of view of a 90mm lens - the lens' "sweet spot" is all that covers the digital sensor. So should one be using say the 80mm lens' lens hood to optimise the flare / contrast protection?

I hope this is not a stupid question; excuse me if it is please.
 

polypal

New Member
Simon,

Interesting point you made here.

It is worth experimenting with a longer shade to see if there is something to be gained in strong backlight situations.

A professional lensshade is the easiest way to allow for a longer more effective shade.
It can be adjusted from the standard setting to the longer setting.

Paul
 

qnu

Banned
Simon,

The answer is yes, you could and should use a longer shade to get optimal shading.
How much of a difference it will make is another matter.

Hasselblad once thought of a new application for an extended Databus. The lens could convey info about how far it was extended to a bellows shade attached on front, and that would adjust its length accordingly and automatically.

Needless to say such thing never appeared.
But the idea is valid: even when focusing the angle of view changes, and a shade could/should be adjusted. Yet again, how much - if anything at all - that would improve results remains to be seen.
 

jotloob

MFF-Patron
@ Simon and @ Q.G.

In my logic , the answer is NO .

The characteristics , the AOV and the behaviour of the lens , you use , remain the same , no matter if you shoot on film 56x56mm , 42x56mm or 37x37mm or 37x48mm sensor .
And the lens does not know which shooting format your are going to use and if you want to crop your (film) image later .
The AOV you see on the screen for the CFV back or an other CF back is smaller , of course . But a DISTAGON 60mm still is a DISTAGON 60mm , even with crop factor of 1.5 , which would simulate a 90mm lens looking at the image we take .
But optimum shading also depends very much on the direction of the light .
 

qnu

Banned
Jürgen,

The light that, when using a larger format, is recorded by that larger format is doing nothing when you are not recording it because you are using a smaller format. Nothing, except bounce around inside the camera, lowering contrast.
It will do that when reflected of a larger sensor or film too. But what are you going to do about that, since you want it to hit the sensor/film?
But when it is not needed, it can, and should be, blocked. It makes a lot of sense to stop it entering in the first place.

And that you do using a longer shade.
Ever seen a shade vignet? Then you will have seen how efficiently a shade can keep light out.
When not using the larger format, we want that vignetting to occur in the bits we are not recording anyway. And we can indeed have that vignetting, by using a longer shade.

So the answer is a resounding YES!
 

jotloob

MFF-Patron
Mmmmmm ....

Q.G. what you say sounds good . I think , I was regarding the issue too much just from the lens point of view .
So I will use my modified "60/60" shade with my SWC and the 60/80 with my DISTAGON when using the CFV .
I have found the vignetting shade for the 250mm , which came with the proshade 6093T . That proofs , what you say .

Simon , I guess you will have a CFV soon . So you should mark the "60/60" shade as FOR FILM ONLY .
 

fotografz

Active Member
The same thing came to mind Jurgen .... the good old slide-in vignetting shade for the 250mm. So, if the CFV back produces a 1.5X crop factor, then the 250 vignetting shade could be used with a 180/4.
 

mr_orange

New Member
Thanks for the link, I have emailed them for a quote; second question, I have a 50mm cfi which came with a screw on attachment, which I presume is for shorter filter size (sorry don't know technical name for it) any way I ended up attaching it to the lens and am now wondering what size filters threads I need for it. Kind of thing I should have done first in hindsight as can't remove it now.
 

qnu

Banned
Paul,

I think it is not a screw-on attachment, but the bayonet mount (!) bayonet 60 to bayonet 70 adapter.
You remove it by pressing the thing towards the lens and twisting it anticlockwise.

The adapter allows use of larger bayonet 70 flters on this lens.
This, because the bayonet 60 filters the older versions took would allow mounting only one without vignetting.
 

simonpg

New Member
Thanks guys - good discussion.

Nice to see you toss a "curve ball" in as well Jurgen!


Well I'd be keen to do the experiment and see how much it matters like QG pointed out; but I DON'T HAVE A CFV!
So, it will just have to wait! And Jurgen that brilliant "Loob special" 60/60 hood will keep getting a workout for film shooting alone for quite a while yet.
 

wbulte

Active Member
Hi Simon,

You could get a Superslide back for song and experiment 'narrower' hoods using that one. In the meantime save money for a CFV

Wilko
 

ngophotographer

New Member
Simon:

The answer to your question is yes. The length of the shade will depend on the focal length/sensor size along with the aperature of the lens.

I would recommend either a "Pro Shade" or Lee shade.

The great thing about digital is you can use the viewfinder to actually see when the hood is vignetting (and in the preview ;))

On a more general "shade" note--If you're doing landscapes during sunrise/sunset a "Pl&" is great too. You cl& it to your tripod and use a 4x5/5x7 size gray card as a shield and you can position it further out if you have low angle light that is showing on the lens.

Hope this helps.

Best regards,

Rich
NGOphotographer
 

simonpg

New Member
Thanks Rich. Yes that was my view.
I use a Pro-shade as well as a "bespoke hand-made" dedicated shade for my CF 60mm courtesy of the clever efforts of Jurgen.
 
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